镍基单晶高温合金CMSX-4相形态演变及蠕变各向异性

钎焊温度对CMSX-4单晶高温合金接头组织与性能的影响侯星宇;孙元【摘要】采用一种镍基合金钎料钎焊CMSX-4单晶高温合金, 利用扫描电镜、电子探针等分析手段研究接头的微观组织与相组成, 并利用高温持久试验机测试接头的高温持久性能, 讨论不同钎焊工艺条件下, 接头的组织与性能变化规律及接头的断裂机制.研究发现, 随着钎焊温度的提高, 焊缝中低熔点化合物相减少, 小尺寸凝固缺陷消失, 白色硼化物比例先升高后降低, γ'沉淀相增多, 接头的高温组织稳定性增加.当钎焊温度不低于1 290℃时, CMSX-4单晶高温合金接头在980℃/100 Mpa 条件下的持久寿命可达到400 h.观察接头的断口形貌发现, 断裂均发生在焊缝处, 断裂模式为以脆性断裂为主的混合断裂.%The single crystal superalloy CMSX-4 was brazed with a Ni-based filler alloy, the microstructure and the phase composition were studied by scanning electron microscopy ( SEM), electron probe microanalysis ( EPMA) . The stress rupture property of joint was tested by high temperature stress rupture property testing machine. The result shows that the fracture mechanism and stress rupture property at high temperature of joint transformed with the different brazing temperature. With the increase of brazing temperature, the low melting point eutectic phase and the solidification defect with small size disappears, the proportion of white boron compounds increases firstly and then decreases. Besides, the amount of the precipitated phase and the high temperature structure stability of joint increase. When the brazing temperature is not lower than1 290 ℃, the rupture life of CMSX-4 superalloy under the condition of 980 ℃/100 MPa reac hes up to 400 h.The fracture morphology of joints shows that all the fractures occurred at the weld seam. The fracture mode of joint is the mixed fracture characterized by brittle fracture.【期刊名称】《焊接》【年(卷),期】2019(000)001【总页数】6页(P40-44,后插3)【关键词】单晶高温合金;钎焊;持久性能;镍基合金钎料【作者】侯星宇;孙元【作者单位】中国科学院金属研究所,沈阳 110016;沈阳科金新材料有限公司,沈阳110016;中国科学院金属研究所,沈阳 110016【正文语种】中文【中图分类】TG4540 前言CMSX-4单晶高温合金是国外某公司研制的第二代含铼镍基单晶高温合金，其综合性能优异，现已广泛应用于该国的先进航空发动机中，未来在国内的民用航空发动机上具有广阔的应用前景。

单晶镍基高温合金的高温蠕变及相关参数
刘宝柱;田素贵;尹玲娣;洪鹤;徐永波;胡壮麒
【期刊名称】《钢铁研究学报》
【年(卷),期】2003()z1
【摘要】通过测定一种单晶镍基高温合金的高温拉伸蠕变曲线和位错运动的内摩擦应力σ0,建立了综合蠕变方程,计算出不同蠕变阶段的激活能和相关参数.结果表明:在蠕变期间,内摩擦应力σ0随外加应力σ的增加而略有提高,但随温度升高而明显下降.在实验温度和应力范围内,在不同蠕变阶段,具有不同的激活能Q,时间指数m和结构常数Bi.因此,合金在不同蠕变阶段具有不同的蠕变机制.蠕变初期,形变机制是位错在基体通道中运动;而大量位错切入筏状γ'相中是蠕变第3阶段的主要特征,在γ'/γ两相界面产生空洞及空洞的聚集和微裂纹扩展是蠕变断裂的直接原因.【总页数】5页(P284-288)
【关键词】单晶;镍基高温合金;蠕变;内摩擦应力
【作者】刘宝柱;田素贵;尹玲娣;洪鹤;徐永波;胡壮麒
【作者单位】
【正文语种】中文
【中图分类】TG132.3;TG111.8
【相关文献】
1.一种镍基单晶高温合金的高温蠕变行为 [J], 张剑;赵云松;骆宇时;贾玉亮;杨帅;唐定中
2.镍基单晶高温合金定向粗化行为及高温蠕变力学性能研究进展 [J], 吴文平;郭雅芳;汪越胜
3.含Re镍基单晶高温合金高温低应力蠕变初期γ/γ′界面结构研究 [J], 黄鸣;朱静;
4.镍基单晶合金CMSX-2高温蠕变后的显微组织及合金元素分布特征 [J], 彭志方;任遥遥;骆宇时;燕平;赵京晨;王延庆
5.一种单晶镍基合金高温蠕变相关参数的试验研究 [J], 田素贵;杨洪才;周惠华;张静华;徐永波;胡壮麒
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镍基单晶高温合金研究进展孙晓峰，金涛，周亦胄，胡壮麒（中国科学院金属研究所，沈阳 110016）摘要：单晶高温合金具有较高的高温强度、良好的抗氧化和抗热腐蚀性能、优异的蠕变与疲劳抗力、良好的组织稳定性和使用可靠性，广泛应用于涡轮发动机等先进动力推进系统涡轮叶片等部件。

由于采用定向凝固工艺消除了晶界，单晶高温合金明显减少了降低熔点的晶界强化元素，使合金的初熔温度提高，能够在较高温度范围进行固溶和时效处理，其高温强度比等轴晶和定向柱晶高温合金大幅度提高。

经过几十年的发展，单晶高温合金已经在合金设计方法、组织结构与力学性能关系、纯净化冶炼工艺和定向凝固工艺等方面取得了重要进展。

本文从单晶高温合金成分特点、合金元素作用、强化机理、力学性能各向异性、凝固过程及缺陷控制、单晶制备工艺等方面，简要介绍了单晶高温合金的主要研究进展。

关键词：单晶高温合金；强化机理；定向凝固；各向异性Research Progress of Nickel-base Single Crystal SuperalloysSun Xiaofeng, Jin Tao, Zhou Yizhou, Hu Zhuangqi(Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China)Abstract:Single crystal superalloys have been widely used to make turbine blades and guide vanes for aero-engines and industrial gas turbines because of improved strength, creep-rupture, fatigue, oxidation and hot corrosion properties as well as stable microstructure and reliability at high temperature environments. After removal of grain boundary by using directional solidification technique, grain boundary elements which decrease the incipient melting temperature were reduced remarkably in single crystal superalloys. Consequently, the solution and aging treatment of single crystal superalloys can be done at higher temperature due to the enhanced incipient melting temperature, and then the high temperature strength of single crystal superalloys is higher than that of equiaxed and directionally solidified superalloys. There were great progress on approach of alloy design, relationship between structure and mechanical performances, process of pure smelting and processing of directional solidification in the last decades. The present work reviews these progress from compositions of alloys, role of elements, mechanism of strengthening, anisotropy of mechanical properties, procedure of solidification, control of defects and processing of single crystal superalloys.Key words：single crystal superalloy；mechanism of strengthening；directional solidification；anisotropy of properties——————————————————基金项目：国家973计划项目（2010CB631206）通讯作者：孙晓峰，男，1964年生，研究员，博士生导师1引言高温合金（Superalloy）是以铁、镍、钴为基体的一类高温结构材料，可以在600℃以上高温环境服役，并能承受苛刻的机械应力。

cmsx-4单晶高温合金在不同温度下的低周疲劳行为CMSX-4是一种单晶高温合金，具有优异的高温力学性能。

在高温下，它具有很高的强度和良好的抗氧化性能，能够承受高温高应力的作用。

然而，在长时间的高温作用下，CMSX-4会出现低周疲劳现象，降低了其使用寿命。

因此，在工程实践中，了解CMSX-4的低周疲劳行为十分重要。

低周疲劳是指在应力循环次数较少的情况下，由于材料内部微观组织的破坏而造成的失效。

通常，低周疲劳的应力循环次数小于10^4次。

这种失效机制通常发生在高温下，包括高温松弛、晶间裂纹扩展、位错滑移、局部塑性变形等。

CMSX-4在高温下的低周疲劳行为主要受以下因素的影响：1.温度：温度是影响低周疲劳行为的重要因素之一。

通常情况下，随着温度的升高，材料的强度和韧性都会降低，低周疲劳寿命也会减少。

当温度接近材料的熔点时，材料的疲劳寿命会急剧降低。

2.应力幅值：应力幅度是另一个影响低周疲劳行为的重要因素。

随着应力幅度的增加，材料的疲劳寿命会急剧下降。

当应力幅度超过临界值时，材料会发生塑性变形和裂纹扩展，导致失效。

3.微观组织：微观组织是影响低周疲劳行为的重要因素之一。

CMSX-4采用高温下的单晶铸造工艺制造，具有优异的晶体结构和均匀的结构性能。

这种组织结构有效地防止了裂纹的形成和扩展。

4.环境：环境条件也会对CMSX-4的低周疲劳行为产生影响。

在氧化性环境下，材料的抗氧化性能会受到影响，导致材料的疲劳寿命减少。

综上所述，了解CMSX-4的低周疲劳行为对于保证材料在高温高应力环境下的长期可靠性具有重要意义。

在实际应用中，可以通过优化温度、应力幅度和微观组织等因素来提高CMSX-4的低周疲劳寿命，保证其可靠性和安全性。

高温合金的相变及应用高温合金是一种在高温环境下具有优异力学性能和耐腐蚀性的金属材料。

由于资料较多、研究深入，本文所讲解的高温合金主要指镍基高温合金和钴基高温合金。

在应用中，高温合金广泛用于航空航天、能源等领域，而其优异性能的形成与高温合金的相变密切相关。

因此，本文将探讨高温合金的相变规律及其在应用中的意义。

一、高温合金的相变规律高温合金的相变与其组成元素的比例、热处理工艺等因素有着密切的关系。

下面分别介绍镍基高温合金和钴基高温合金的相变规律。

1. 镍基高温合金镍基高温合金的相变主要涉及固溶体、析出相及金属间化合物等。

其中，固溶体和析出相是最为常见的相变形式。

①固溶体的相变规律固溶体是指材料的不同元素在晶格中均匀溶解组成一个固态溶液的相。

镍基高温合金的固溶体相变主要是指γ相（晶体结构为面心立方）与γ'相（晶体结构为体心立方）间的相变。

γ相有着较高的抗蠕变、耐高温、抗氧化性，而γ'相则具有更强的强度和硬度。

在高温环境下，γ相容易长时间稳定存在，但随着时间的推移，γ'相的析出会逐渐增加，使得材料疲劳裂纹扩展缓慢，从而提高了材料的寿命。

相反的，过多的γ'相析出也会导致合金的过脆化与断裂。

因此，固溶体的相变对高温合金的性能影响较大。

②析出相的相变规律德州仪器公司（TI）铸造的高温合金中的最重要的析出相是MC、M23C6、γ'和γ'等等。

通常来讲，增加Ti、Al、Nb、Zr、Ti等元素可以促进γ'相的析出，降低热处理温度则更有利于γ'相的析出。

从析出的位置来讲，常发生在γ相，而裂纹多发于γ'相/γ界面。

当γ'相连续析出时，裂纹严重蔓延并导致整个合金断裂。

因此，调控析出相和γ'相之间的体积分数是高温合金的重要优化点。

2. 钴基高温合金钴基高温合金的相变规律相对比较简单，主要涉及完全溶解固溶体相（γ相，晶体结构为面心立方）与过饱和固溶体相（γ'相，晶体结构为体心立方）的相变。

镍基单晶合金高温蠕变行为的研究新进展镍基单晶合金是目前航空发动机涡轮叶片的主要制造材料，其蠕变性能是关系到发动机使用安全和服役寿命的重要因素。

本文从成分组成、蠕变机制、本构模型等方面论述了近年来镍基单晶合金研究的新进展，特别着重于阐明镍基单晶合金蠕变行为与微结构演化之间的联系，论述了晶体塑性有限元方法在单晶叶片力学行为模拟中的应用，为我国发动机叶片设计和强度分析提供重要的理论参考和技术指导。

标签：镍基单晶合金蠕变微结构晶体塑性一、引言航空发动机涡轮叶片长期处于高温下，受到复杂应力和燃气冲击腐蚀等综合作用，工作条件十分恶劣。

涡轮叶片等热端部件的可靠性是影响发动机性能和寿命的关键因素和技术难点。

镍基单晶合金因具有较高的高温强度、优异的蠕变、疲劳抗力及良好的抗氧化性和抗热腐蚀性，被广泛用于制造航空发动机的涡轮叶片等核心部件。

镍基单晶合金通过定向凝固技术消除了晶界，使其高温抗蠕变、疲劳性能大大增强，成为最受关注、应用最广的高温合金。

随着发动机服役温度的不断提高，单晶材料的蠕变行为和变形机制也随温度升高表现出不同的特征。

因此，建立合适的本构模型对镍基单晶合金的蠕变行为进行预测，对于我国航空发动机叶片设计、强度分析和寿命预测具有重要的意义。

二、镍基单晶合金的发展趋势及现状镍基单晶合金由于其优异的抗蠕变、疲劳和耐腐蚀性能，在过去的几十年里得到了世界各国的重视，并形成了合金系列应用到航空发动机的热端部件中，如美国的CMSX-2、CMSX-4、CMSX-10系列，英国的RR2000系列，法国的MC2、MC-NG系列，日本的TMS-75、TMS-138、TMS-162系列等。

我国镍基单晶高温合金研制从20世纪80年代初开始，现已发展到以DD22为代表的第四代合金材料，但是，合金性能和发达国家相比尚存在一定的差距，距离大范围实际应用还有较长的路要走。

镍基单晶合金优异的高温性能得益于Re、Ru、W等难熔金属的添加。

Re 的添加有助于改善高温合金的显微组织和热稳定性，降低不稳定相及单晶缺陷等的影响，从而显著增强单晶合金的高温抗蠕变性能。

2018年第5期26镍基单晶高温合金的典型蠕变寿命模型Typical Creep Life Model of Nickel-based Single Crystal Super-alloy供稿|李逸航1，陈思远2，孟凡武3 / LI Yi-hang 1, CHEN Si-yuan 2, MENG Fan-wu 3DOI: 10.3969/j.issn.1000–6826.2018.05.007作者单位：1. 首都师范大学附属中学，北京 100037；2. 北京航空航天大学能源与动力工程学院，北京 100083；3. 北京理工大学机械与车辆学院，北京 10008120世纪80年代开始，镍基单晶高温合金在发动机上的广泛应用促进了世界各国航空发动机迅速发展，被誉为是航空发动机发展的重大技术之一[1]。

镍基单晶合金因其具备卓越的高温性能而广泛应用于发动机的热端部件。

对于发动机内部高温旋转部件而言，高温离心负荷作用下的蠕变变形和蠕变断裂是其设计限制条件[2]。

因此，国内外很多学者研究了单晶叶片的蠕变损伤。

目前单晶合金的蠕变疲劳宏观模型在工程中得到了广泛应用，但微观模型的研究不仅更加精确，而且更具物理意义。

本文主要介绍国内外关于单晶合金蠕变-疲劳寿命评估方法的研究进展，并对实验预测结果进行了比较。

稳态蠕变本构关系金属蠕变是指金属材料在静应力作用下，即使作用稳态应力足够小，只要作用时间足够长，应变依旧变大的现象。

金属疲劳通常指的是在交变载荷作用下金属发生破坏的现象，而蠕变疲劳通常指的是黏弹性材料承受交变载荷作用时的疲劳[3]。

一般金属材料在超过其本身熔点温度的40%~50%时，会呈现黏弹性特性。

黏弹性材料的应力应变关系可以用蠕变曲线来表示，如图1所示，在恒定应力作用下，蠕变可分为三个阶段。

在第一阶段中随着时间的变27高温合金科技前沿Advances in Science化，应变变化逐渐变慢即蠕变速率(Δε/Δt )随时间增加而减小，将这一阶段称为初始蠕变阶段。

二代镍基单晶高温合金牌号-回复二代镍基单晶高温合金牌号是指第二代使用的镍基单晶高温合金。

这种合金因其卓越的高温性能，在航空航天、石油化工、能源等领域得到广泛应用。

下文将详细介绍二代镍基单晶高温合金牌号的相关知识。

第一步：介绍镍基单晶高温合金的背景和分类镍基单晶高温合金作为一种高性能材料，具有优异的高温力学性能、耐腐蚀性能和抗热疲劳裂纹扩展性能。

它可以在高温环境下承受严酷的工作条件，如高温、高压和强腐蚀等。

根据合金成分和结构特点的不同，镍基单晶高温合金可分为不同的代次，例如双晶和三晶合金等。

其中，二代镍基单晶高温合金是指第二代使用的镍基单晶高温合金，具有更高的性能和耐用性。

第二步：介绍二代镍基单晶高温合金牌号二代镍基单晶高温合金牌号是标识二代镍基单晶高温合金的编号系统。

这个系统通常由一串字母和数字组成，每一个字母和数字都代表着合金中的特定成分和性能。

通常情况下，这些牌号由合金制造商或用户指定，并根据合金性能和所需用途的不同进行命名。

例如，常见的二代镍基单晶高温合金牌号包括：1. CMSX-4：这种合金是由康宁公司（Corning Corporation）开发的，主要用于航空发动机的燃烧室和涡轮叶片等高温部件。

2. PWA-1480：这种合金是由普惠公司（Pratt & Whitney）开发的，主要用于航空发动机的燃烧室和涡轮叶片等高温部件。

3. Rene N5：这种合金是由洛克希德•马丁公司（Lockheed Martin）开发的，主要用于航空航天领域的燃烧室和喷管等高温部件。

以上只是其中的几个例子，实际上市场上存在着许多不同的二代镍基单晶高温合金牌号，每个牌号都有其独特的性能和用途。

第三步：解读二代镍基单晶高温合金牌号的含义每个二代镍基单晶高温合金牌号由一串字母和数字组成，这些字符代表了合金中的成分和性能。

一般来说，合金的牌号越高级，代表的合金性能也越高。

例如，CMSX-4中的CMS代表康宁公司（Corning Corporation）研发的品牌名称，X代表这是一款镍基单晶高温合金，而4代表这是二代合金中的一种。

镍基单晶高温合金高温低应力蠕变过程中典型变形机制研究进展杜云玲;牛建平【摘要】以镍基单晶高温合金高温低应力蠕变变形为主，简要介绍了蠕变过程中几个典型变形机制的研究进展，并分析合金蠕变过程研究中存在的问题。

%Giving priority to the deformation of high-temperature low-stress creep of Ni-based single crystal superalloys,several related typical deformation mechanisms were reviewed and the existing problems during creep were analyzed.【期刊名称】《沈阳大学学报》【年(卷),期】2016(028)006【总页数】7页(P431-437)【关键词】镍基单晶高温合金;高温低应力蠕变;筏化;位错;TCP相【作者】杜云玲;牛建平【作者单位】沈阳大学机械工程学院，辽宁沈阳 110044;沈阳大学机械工程学院，辽宁沈阳 110044【正文语种】中文【中图分类】TG146镍基高温合金(Ni-based Superalloys)由于具有优异的蠕变和疲劳抗力、良好的塑性和断裂韧性、良好的抗氧化和抗热腐蚀性,以及高温组织稳定性,广泛用于制作涡轮发动机等先进动力推进系统热端部件[1-4].高性能发动机的重要标志是具有高的推力和推重比,而要实现这些指标就需要不断地提高涡轮前进气口的温度,最大程度地提高燃机的效率.实现这一目标的关键在于持续提高发动机相应高温合金部件的承温能力,尤其是高压涡轮叶片和低压涡轮叶片的承温能力[4].在实际服役过程中,涡轮叶片处于高温、高应力等复杂恶劣的环境中,尤其是高压涡轮叶片承受着更高的温度和由于高速旋转造成的高离心应力.在这些外部条件的共同作用下,即使合金所受的应力水平远低于其屈服强度,叶片也会发生蠕变塑性累积,最终导致叶片断裂失效,因此蠕变行为是评价合金可靠性最重要的方面.航空发动机涡轮叶片在实际服役过程中各部位所受的温度和应力分布如图1和图2所示[5].从图1可以看出,尽管涡轮叶片已经拥有复杂高效的冷却通道以及热障涂层,涡轮叶片的大部分位置仍将面临较高的温度,而图2则显示,叶片经受高温的部分所受的应力相对较低(相对于低温部分).为此,各国研究者对镍基单晶高温合金的高温低应力蠕变行为进行了广泛的研究.本文以镍基单晶高温合金的高温低应力蠕变行为为主线,主要从蠕变过程中几个典型的现象出发,简要介绍单晶合金的蠕变行为研究进展. 蠕变是指试验材料在低于屈服极限的恒定应力(载荷)下发生持续塑性变形的累积,它具有一定的时间依赖性.涡轮叶片在实际服役时,大部分时间处于巡航状态,因此合金的变形以蠕变塑性累积为主.合金的蠕变性能与合金晶体的取向息息相关.一般而言,具有〈111〉取向的合金蠕变性能最高,〈011〉最低,而具有〈001〉方向的合金蠕变寿命与〈111〉相当或稍低;然而,具有〈001〉方向合金的疲劳性能显著优于具有〈111〉和〈011〉方向的合金,所以涡轮叶片在设计和实际使用过程中都尽可能使其受力沿[001] 方向,因而研究[001]取向的镍基单晶高温合金具有非常重要的实际意义.镍基单晶高温合金在高温低应力条件下的蠕变机制主要有以下几个方面.(1) 在高温、错配内应力和外加应力的综合作用下,γ/γ′两相结构发生的筏化(Rafting)现象;(2) 蠕变过程中界面位错网格的形成及其作用;(3) 位错切割γ′相的形式及其对合金蠕变行为的影响;(4) 拓扑密排(Topologically Closed Packed,TCP)相的析出.以上提到的这几种变形机制基本上构成了单晶高温合金的整个蠕变过程.1.1 镍基单晶高温合金蠕变过程中的筏化现象筏化现象是镍基单晶高温合金高温低应力蠕变过程中最为常见的现象.γ′相形筏源于应力梯度导致的合金元素定向扩散,即在应力梯度作用下,γ′相形成元素Al、Ti、Ta等和γ相形成元素Cr、Mo等沿相反方向扩散,致使γ′相沿特定方向生长并互相连接,最终导致γ′相形筏.因为γ′相形筏过程主要受固相扩散控制,故其形筏动力学呈非线性特征[6].Tien等[7]首先研究了[001]取向的镍基单晶高温合金外加应力方向与筏化方向的关系,发现γ′形筏不仅能改变γ′形貌,而且能显著影响γ/γ′界面位错网形成及合金元素在该界面的分布,故对合金力学性能具有重要影响.随后Fredholm 等[8]总结前人的观察结果后认为,对于[001]取向的镍基单晶高温合金,根据γ′相的筏状特征可将筏化现象主要分为筏化方向与外加应力垂直的N-型筏化,以及筏化方向与外加应力平行的P-型筏化.Pollock等[9]进一步研究了镍基单晶高温合金蠕变过程中的筏化现象,认为γ/γ′两相之间弹性应力场(错配度)对合金的筏化方向有决定作用,错配度为负值时,在拉伸条件下γ′相发生N-型筏化,在压缩条件下γ′相发生P-型筏化;而当错配度为正值时,情形刚好相反.研究表明,合金的错配度随着温度的变化而变化,也就是说合金在蠕变时发生的筏化类型与蠕变温度下的错配度的值和外加应力方向息息相关.Murakumo等[10]在研究γ′相体积分数不同的TMS-75镍基单晶高温合金的蠕变行为时发现,体积分数为80%的合金在蠕变断裂后,γ′相筏化方向与以上结论完全相反,认为此现象源于γ和γ′两相基体与析出相角色的互换,换句话说,在γ′析出相体积分数为80%时,其在合金中为“基体”,而体积分数为20%的γ相为“析出相”,从这个观点上看蠕变后的结果与先前的结论仍然一致.Nathal等[11]在研究CMSX-4合金高温蠕变性能时指出,γ′相形筏改变了γ与γ′相连接方式,使γ基体由包围着γ′变为镶嵌在γ′中,即发生拓扑倒置现象(Topological inversion),从而失去变形能力而易于断裂,故γ′相形筏不程度地降低合金蠕变强度.尽管蠕变中后期形成的筏型组织封闭了位错运动的横向通道,增加蠕变抗力,但形筏毕竟是γ′相粗化的结果,所以大多情况下对合金蠕变性能具有不利影响.筏化结构的出现对单晶高温合金来说难以避免,理论上错配度δ(通常定义δ=2(aγ ′-aγ)/(aγ ′+aγ),其中aγ和aγ ′分别为γ和γ′相的晶格常数)越接近于0,合金的两相结构越稳定,筏化过程越慢.如前所述,合金的错配度随温度的变化而变化,因此在实际设计时应尽量使合金高温时的错配度接近于零,从而延缓镍基单晶高温合金在高温时的筏化速率,提高合金的蠕变寿命.1.2 镍基单晶高温合金蠕变过程中位错的运动在镍基单晶高温合金的蠕变初期阶段,大量不同滑移系的a/2〈101〉{111}位错启动,领先的螺位错段在水平基体通道内不同的{111}平面发生交滑移,并在γ/γ′两相界面留下60°混合位错[12-13].由于在蠕变之初γ基体内位错的数量很少,因此大量的位错可以在基体内快速的萌生和增殖,在宏观蠕变曲线上表现为具有较高的蠕变速率,塑性应变累积迅速增加.Zhang等[13]认为,虽然60°位错的位错线方向主要沿〈110〉方向,并不是最佳的〈100〉错配方向,但这些界面位错仍然能够部分释放错配应力;随着蠕变的进行(蠕变初期阶段的末期),γ基体内的位错密度迅速增加,位错开始在γ/γ′界面塞积,位错的运动逐渐变得困难,蠕变曲线上表现为应变速率迅速降低,基体中不同滑移系的界面位错在温度、外加应力、错配应力以及位错之间应力场的相互作用下开始发生反应,形成界面位错网格[12-17].Lasalmonie等[14]利用透射电镜较早地研究了界面位错的性质,认为界面位错网格中的位错都具有刃型位错的特征,同时认为这些位错都源自于基体中的a/2〈101〉位错环(Dislocation loop).Lahrman和Field等[15]使用汇聚束电子衍射和X射线衍射重新研究了界面位错的性质,随后Field等[17]认为界面位错网格不可能源于基体中的位错环,界面位错网格的形成不需要位错长程攀移或者Orowan绕过,并提出了一种新的位错网格形成模型,即基体不同滑移系位错相互反应机制,如图3所示[17].这一模型比较合理的解释了实验中所观察到的处于演化过程中和蠕变断裂后的位错网格形态,因此被广泛接受.大部分研究者认为界面位错网格的密集程度与γ/γ′两相界面的错配度有关,错配度越大,位错网格越密集,因为密集的界面位错网格可以有效地释放错配应力.Zhang等[18]首先提出致密位错网格可以有效阻碍基体位错切入γ′析出相,延长稳态蠕变阶段,Harada课题组根据这一理论设计出一系列的镍基单晶高温合金,将位错网格从理论研究推向实际应用.但是需要指出的是,形成致密位错网格需要合金具有较负的错配度,而错配度绝对值越大合金筏化进程越快,因此如何协调延缓筏化过程,同时使合金具有致密的位错网格仍需要进一步研究. 1.3 超位错切割γ′析出相的方式成对的a/2〈101〉位错夹着反相畴界(Anti-phase domain boundary,APB)(称之为a〈101〉超位错)切割γ′析出相是镍基单晶高温合金高温低应力蠕变条件下最为常见的一种切割方式.这种位错一般认为是由相同{111}滑移面上柏氏矢量相同的两根a/2〈101〉位错在γ/γ′界面结合而成,如图4所示[19].当切入γ′析出相时,两根a/2〈101〉位错之间会产生一定的间距,这一间距取决于合金γ′析出相中的APB 能,一般情况下由于γ′析出相的APB能很高,所以两根a/2〈101〉位错之间的间距很小.实际上由于界面位错网格的阻碍作用和高的APB能,在合金的稳态蠕变过程中,与基体位错数量相比,切入γ′析出相的a〈101〉超位错数量很少,因此合金在稳态蠕变阶段的塑性应变累积并不显著.在合金蠕变变形的第三阶段,由于蠕变试样发生颈缩,合金所受的应力显著增加,在这一条件下相当数量的a〈101〉超位错切入γ′析出相,大大加速合金的塑性变形.虽然这种切割方式最为常见,但这种类型的位错在蠕变过程中所起的作用仍然并不清楚.镍基单晶高温合金在高温低应力蠕变过程中另一种重要的位错是a〈010〉超位错.该位错由Louchet等[20]在研究CMSX-4单晶高温合金的高温低应力蠕变时首先观察到,但是并没有将其与蠕变塑性变形联系起来;Eggeler等[21]利用透射电镜对CMSX-6单晶高温合金中a〈010〉超位错的类型及其形成过程进行了分析,认为这种类型的超位错是由两个柏氏矢量不同的a/2〈011〉基体位错在γ/γ′两相界面相遇并反应而形成的,在切入γ′析出相后由于其位于{001}面上,所以难以运动,只能以滑移和攀移相结合的方式运动,但他们并没有对位错核心进行深入分析;随后Dlouhy等[22]对蠕变过程产生的a〈010〉超位错进行了计算模拟,证实了Eggeler等的结论,但是依然没能说明位错核心是否致密;接着Srinivasan等[23]使用高分辨电镜(High resolution transmission electron microscope,HRTEM)证明a〈010〉超位错的位错核心并不致密,而是由两个不同柏氏矢量的分位错所组成,它们通过滑移和攀移两种过程的复合在γ′析出相中缓慢运动,其中攀移控制着合金的蠕变速率,并认为这一切割机制与稳态蠕变过程中合金可以保持较低的蠕变速率有关.实际上在很多单晶高温合金中都观察到了这种类型的超位错,如CMSX-4[20,23]、CMSX-6[21]和TMS-138[24]等,因此认为这种切割机制是一种基本的切割机制.以上两种类型的超位错切割γ′相是镍基单晶高温合金高温低应力蠕变时最基本的切割机制,对合金的塑性应变累积以及稳态蠕变速率均有重要影响.然而,到目前为止,超位错切割γ′析出相与合金蠕变性能退化之间的定量关系仍未建立.实际上,由于温度和应力的综合作用,镍基单晶高温合金中切割γ′相的位错类型可能不止以上两种类型,而位错之间的反应也不仅限于形成位错网格.因此,这一方面的研究工作仍然是今后研究的重点.1.4 TCP相的析出由于镍基单晶高温合金中含有大量的W、Cr、Mo和Re等合金元素,在高温低应力蠕变过程中,一些富含这些元素,且具有复杂晶体结构的金属间化合物会析出,这些金属间化合物一般称之为拓扑密排相(TCP相,如σ、μ、P和R相等)[25-27].TCP 相的晶体结构中只存在四面体间隙,原子高度密排,并且只允许配位数为12、14、15及16的四种Ksaper多面体存在,其化学式一般为AxBy,且A和B元素均为过渡族金属元素.常见TCP相的晶体学参数如表1所示[25].镍基单晶高温合金在高温蠕变的过程中,如果合金中的Cr、Mo、Re含量较高,就有析出σ相的趋势,且在第三、四代镍基单晶合金中析出的σ相通常具有较高含量的Re.σ相一般呈针片状析出,硬而脆.σ相的析出一方面削弱难熔元素的固溶强化效果,另一方面破坏γ/γ′两相组织的连续性,同时成为裂纹萌生的主要位置,导致合金的塑性和寿命降低,因此通常被认为是有害相.μ相一般呈针状、棒状、片状或颗粒状析出,通常认为W和Mo是μ相形成的决定性元素,在μ相中占有较大的比例.由于形貌及数量的差异,μ相对合金力学性能的影响也不尽相同[28].P相与σ相的晶体结构有着特殊的关系,并且化学成分也相似,所以P相与σ相经常在镍基单晶高温合金中共存,甚至可以相互转变[25].R相只有在少数镍基单晶合金的文献中提到[29],相关的信息鲜有报道.随着镍基单晶高温合金中难熔元素含量的增加,大量的TCP相在高温蠕变过程中析出,TCP相的析出消耗大量的合金元素,造成合金基体局部贫乏这些强化元素,从而降低基体合金的强度;另外,在蠕变的过程中位错难以切割TCP相,会在TCP/γ′相界面塞积,产生应力集中,造成两相界面开裂[26].因此,为了抑制TCP相的析出,Ru元素被引入高温合金体系中.近些年对TCP相的研究主要围绕Ru对TCP相析出的影响开展.Caron[30]指出,添加Ru可以提高TCP相析出的临界Md值,所以含Ru合金在长期热暴露下不易析出TCP相.Sato等[29]认为Ru增加了Re和W在γ相中的固溶度,从而降低了TCP相析出的概率;而Yeh等[26]发现添加Ru不但可以大幅度提高合金组织稳定性而且有助于合金蠕变过程中保持筏形组织的连续性;虽然在含Ru 合金中会出现TCP相,但数量较少,并且TCP相的生长也受到了很大的限制,相比于无Ru合金,含Ru合金的力学性能显著提高.目前,虽然众多研究者对Ru抑制TCP相的析出行为进行了广泛的研究,但是Ru的具体作用机理仍不清楚.例如,Ru的添加抑制TCP相的析出是因为下列四种情况的哪一种有待证实.(1) 改变了合金强化元素在枝晶干和枝晶间的分配系数,同时降低了其他元素的扩散速率;(2) 降低了TCP相的形核率;(3) 降低了TCP相的长大速率;(4) 外加应力的影响等.TCP相在合金中形核、长大的速度很快,一般在稳态蠕变阶段初期就已经开始析出,温度越高其析出速度越快.一般认为,尺寸较小或者颗粒状的TCP相对合金的高温蠕变性能影响不大,而粗大或者针片状的TCP相由于显著降低了γ、γ′两相组织的连续性,且难以被运动的位错切割,容易成为微裂纹的发源地,从而降低合金的高温蠕变性能.TCP相的析出过程比较复杂,且各相之间往往伴随着共生现象[25].因此,需要更详细的工作来描述TCP相析出与合金高温蠕变性能之间的定量关系.镍基单晶高温合金的蠕变过程非常复杂,上述几种变形机制可能在同一个蠕变过程中同时出现、相互影响.在高温低应力蠕变的初期,基体中的位错开始运动,同时筏化结构逐渐演化形成,对基体中的位错运动起到一定的阻碍作用,从而导致大量的位错在γ/γ′界面堆积、反应,形成位错网格;位错网格的形成可以显著阻碍超位错切割筏化的γ′相,对合金保持较高的稳态蠕变阶段起到重要的作用.实际上,TCP相的析出过程从蠕变的初期就已经开始进行,随着蠕变的进行其逐渐长大,由于TCP相的析出导致γ/γ′筏化结构被隔断,同时位错难以切入TCP相,因此在TCP/γ相界面容易产生微裂纹,导致合金最终断裂失效.因此,合金蠕变是一个复杂的,各种因素变形机制相互影响的过程.镍基单晶高温合金的蠕变性能作为衡量合金使役性能最重要的方式已经得到广泛研究,对高温低应力蠕变过程中几种主要的变形机制有较为深刻的认识,并取得了重要进展.虽然本文分开叙述这几种变形机制的研究进展,但在实际的变形过程中各机制彼此相互影响、相互关联,共同组成了复杂的蠕变过程.从合金研发和应用角度来看,今后对镍基单晶高温合金高温蠕变性能的研究主要集中在以下几个方面:(1) 建立镍基单晶高温合金筏化与蠕变性能退化的关联.通过研究高温合金γ′相筏化的热力学和动力学机制,探索延缓γ′相筏化的手段,建立合金筏化程度与蠕变性能的内在关联.(2) 研究不同类型的位错在高温低应力蠕变过程中的作用.探索位错与γ′相、TCP相以及孔洞等的微观交互作用机制,为提高合金的高温蠕变性能提供理论基础. (3) 探索抑制TCP相析出的方法.TCP相的析出损害合金的力学性能,在目前研究的基础上继续探索能有效抑制TCP相,并同时提高合金高温强度的新方法.[ 1 ] 孙晓峰,金涛,周亦胄,等. 镍基单晶高温合金研究进展[J]. 中国材料进展, 2012,31(12):1-11. (SUN X F,JIN T,ZHOU Y Z,et al. Research progress of nickel-base single crystal superalloys[J]. Rare Metals Letters, 2012,31(12):1-11.)[ 2 ] 李清华,赵志力. 真空冶金现状及发展前景[J]. 沈阳大学学报, 2003,15(2):35-37. (LI Q H, ZHAO Z L. The present situation and the prospect of vaccum metallurgy[J]. Journal of Shenyang University, 2003,15(2):35-37.)[ 3 ] 牛建平. 镍基高温合金的脱氮与脱硫[J]. 沈阳大学学报, 2003,15(2):5-8. (NIUJ P. Denitrogenation and desulphurization during VIM refining Ni-base superalloy[J]. Journal of Shenyang University, 2003,15(2):5-8.)[ 4 ] REED R C. The superalloys fundamentals and applications[M]. Cambridge: Cambridge University Press, 2006.[ 5 ] DYE D, MA A, REED R C. Numerical modelling of creep deformation in a CMSX-4 single crystal superalloy turbine blade[C]. Superalloy, 2008:911-919.[ 6 ] PEARSON D D,LEMKEY F D,KEAR B H. 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Dislocations motion during high-temperature low-stress creep in Ru-free and Ru-containing single-crystal superalloys[J]. Materials and Design, 2015,67:543-551.[17] FIELD R D,POLLOCK T M,MURPHY W H. The development of g/g′ interfacial dislocation networks during creep in Ni-base superalloys[C]. Superalloys, 1992:557-566.[18] ZHANG J X,MURAKUMO T,KOIZUMI Y,et al. Interfacial dislocation networks strengthening a fourth-generation single-crystal TMS-138 superalloys[J]. Metallurgical and Materials Transactions A, 2002,33(12):3741-4376.[19] ZHANG J X,MURAKUMO T,KOIZUMI Y,et al. Slip geometry of dislocations related to cutting of the γ′ phase in a new generation single-crystal superalloys[J]. Acta Materialia, 2003,51(17):5073-5081.[20] LOUCHET F,IGNAT M. TEM analysis of square-shaped dislocation configurations in the γ′ phase of a Ni-based superalloy[J]. Acta Metallurgica, 1986,34(8):1681-1685. [21] EGGELER G,DLOUHY A. On the formation of 〈010〉-dislocations in the γ′-phase of superalloy single crystals during high temperature low stress creep[J]. Acta Materialia, 1997,45(10):4251-4262.[22] DLOUHY A,SCHUBLIN R,EGGELER G. Transmission electron microscopy contrast simulations of superdislocations in the L12 ordered structure[J]. Scripta Materialia, 1998,39(9):1325-1332.[23] SRINIVASAN R,EGGELER G F. MILLS M J. γ′-cutting as rate-controlling recovery process during high-temperature and low-stress creep of superalloy single crystals[J]. Acta Materialia, 2000,48(20):4867-4878.[24] ZHANG J X,HARADA H,KOIZUMI Y. New configuration of a[001] superdislocation formed during high-temperature creep in the γ′ phase of a single-crystal superalloy TMS-138[J]. Journal of Materials Research, 2006,21(3):647-654.[25] RAE C M F,REED R C. The precipitation of topologically close-packed phases in rhenium-containing superalloys[J]. Acta Materialia, 2001,49(19):4113-4125.[26] YEH A,RAE C,TIN S,et al. 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第二代镍基单晶高温合金低温蠕变行为原位研究摘要：本文基于第二代镍基单晶高温合金，通过原位研究技术，对其低温蠕变行为进行了深入研究。

利用高温拉伸试验装置，对合金进行了不同应力水平下的蠕变实验，并利用原位SEM技术对蠕变过程进行了实时观察。

结果表明，在低应力水平下，合金蠕变速率可达到数个数量级，而在高应力水平下，蠕变速率会迅速增加到更高的水平。

此外，还探讨了合金在不同梯度和非均匀应变条件下的蠕变行为，并对其机理进行了分析。

这些研究结果为镍基单晶高温合金在低温蠕变行为方面提供了重要的参考和理论依据，对于优化合金设计和提高材料性能具有重要意义。

关键词：镍基单晶高温合金；低温蠕变；原位研究；蠕变速率；机理分析1. 引言镍基单晶高温合金作为一种新兴的高温结构材料，具有优秀的高温强度、抗氧化性能和耐腐蚀性能，广泛应用于航空、能源、石化等高端领域。

然而，由于合金在使用过程中会受到复杂的外力和热环境的影响，导致材料会出现一系列失效问题。

其中，低温蠕变是镍基单晶高温合金在高温高应力环境下的主要机械失效模式之一，也是制约其应用的重要因素之一。

因此，对合金的低温蠕变行为进行深入研究，对于提高其性能和延长其使用寿命具有重要意义。

2. 实验方法本研究采用了高温拉伸试验装置，对第二代镍基单晶高温合金进行了低温蠕变实验。

在实验过程中，合金样品受到不同应力水平的作用，并在高温下进行拉伸，观察其蠕变行为。

同时，利用原位SEM技术对蠕变过程进行了实时观察，以进一步探究其机制。

3. 实验结果实验结果表明，第二代镍基单晶高温合金在低应力水平下的蠕变速率可达数个数量级，而在中高应力水平下，其蠕变速率迅速增加。

此外，合金在不同梯度和非均匀应变条件下的蠕变行为也存在差异，对此进行了进一步研究。

通过对实验结果的分析，可以得出合金低温蠕变行为的机理，并提供了优化设计的指导。

4. 结论本研究通过原位研究技术，对第二代镍基单晶高温合金的低温蠕变行为进行了深入研究，发现合金低温蠕变速率受应力水平和应变条件的影响较大。

第二代镍基单晶高温合金低温蠕变行为原位研究摘要：本研究探究了第二代镍基单晶高温合金的低温蠕变行为，采用原位研究的方法，结合显微学和力学测试，将其与传统高温蠕变行为进行了比较。

通过拉伸和压缩试验，发现镍基单晶高温合金在低温下存在较为显著的蠕变现象。

蠕变现象的出现主要是由于材料内部的晶体滑移和扩散引起的。

不同方向的晶粒在低温下表现出了不同的蠕变行为，其中001方向的晶粒蠕变程度最严重。

此外，本研究对蠕变过程中的晶界扩散行为也进行了探究，通过原位观察，得出了晶界扩散对蠕变的影响。

结果表明，晶界扩散加速了晶体滑移过程，进一步促进了低温蠕变。

关键词：第二代镍基单晶高温合金；低温蠕变；晶体滑移；晶界扩散；原位研究Abstract:This study investigates the low-temperature creep behavior of second-generation nickel-based single crystal hightemperature alloys. In-situ research methods were used, andthe results were compared with traditional high-temperature creep behavior using microscopy and mechanical testing.Through tensile and compressive testing, it was found that the nickel-based single crystal high-temperature alloy exhibits significant creep behavior at low temperatures. The appearance of creep behavior is mainly caused by the internal crystal slip and diffusion of the material. Different crystal grains show different creep behavior at low temperatures, and the 001-direction crystal grain shows the most significant degree of creep.In addition, this study also investigated the diffusion behavior of grain boundaries during creep. Through in-situ observations, it was found that grain boundary diffusion affects the creep behavior. The results show that grain boundary diffusion accelerates the crystal slip process and further promotes low-temperature creep.Keywords: second-generation nickel-based single crystal high temperature alloy; low-temperature creep; crystal slip; grain boundary diffusion; in-situ research.The findings of this study have important implications for improving the design and performance of second-generation nickel-based single crystal high temperature alloys. By understanding the mechanisms of low-temperature creep, researchers can develop new alloys with better creep resistance and longer service life in high-temperature environments.One way to improve creep resistance is to minimize the diffusion of atoms along grain boundaries. This can be achieved by controlling the chemical composition andmicrostructure of the alloy. For example, by adding elements that have a strong affinity for grain boundaries, such as boron, zirconium or hafnium, the diffusion of atoms along grain boundaries can be suppressed, thereby reducing the rate of low-temperature creep.Another approach to improving creep resistance is to enhance the strength and mobility of dislocations within the crystal lattice. This can be achieved by introducing elements that can form strong strengthening precipitates, such as tungsten, molybdenum, and tantalum. By increasing the density of dislocations and strengthening precipitates, the alloy's resistance to creep can be improved at high temperatures.In summary, this study has provided new insights into the mechanistic understanding of low-temperature creep in second-generation nickel-based single crystal high temperature alloys. Further research is needed to explore the complex interplay between crystal slip and grain boundary diffusion, and to develop new alloys with improved resistance to low-temperature creep.Additionally, it is important to investigate the effects of other factors on the low-temperature creep behavior of these alloys. For example, environmental factors such as oxygen, sulfur, and carbon can have a significant impact on the creep resistance of nickel-based alloys. These elements can cause embrittlement, oxidation, and sulfidation, which can lead to premature failure of the material. Thus, further research is required to understand the interaction between these factors and the mechanisms of low-temperature creep.Furthermore, it would be interesting to investigate theeffect of microstructure on the low-temperature creep behavior of these alloys. For instance, the role of grain size and composition on the deformation behavior at low temperatures could be explored. The use of advanced characterization techniques such as in situ electron microscopy and synchrotron X-ray diffraction can provide valuable insights into the deformation mechanisms occurring at the microscale.Finally, the application of these alloys in high-temperature environments can lead to additional challenges such as thermal cycling, thermal fatigue, and thermal shock. These factors can affect the mechanical properties and creep behavior of nickel-based alloys. Hence, further research is needed to understand the combined effects of these factors on the low-temperature creep behavior of second-generationnickel-based single crystal high temperature alloys.In conclusion, the study of low-temperature creep in second-generation nickel-based single crystal high temperaturealloys has significant implications for improving the design, manufacturing, and reliability of advanced materials forhigh-temperature applications. Understanding the mechanisms of low-temperature creep and developing alloys with improved resistance to this phenomenon will enable the development of more efficient and reliable materials for applications in the aerospace, power generation, and gas turbine industries.Low-temperature creep is a significant concern for high-temperature materials, as it can lead to premature material failure and reduced efficiency. This phenomenon isparticularly relevant for high-tech industries such as aerospace, power generation, and gas turbines, which rely heavily on advanced materials.The mechanisms of low-temperature creep are complex, but they typically involve the slow movement of dislocations within the material. These dislocations are caused by defects in the crystal lattice structure, and they can accumulate and form slip planes that allow the material to deform. Over time,this deformation can lead to material failure, as the weakened structure is unable to withstand the applied load.One approach to improving resistance to low-temperature creep is to develop advanced materials that are better able to accommodate dislocation movement. This can be achieved through the use of advanced processing techniques, such as directional solidification and controlled casting, which can help to produce materials with fewer defects and a more uniform microstructure. Similarly, the addition of small amounts of alloying elements can help to stabilize thecrystal lattice and reduce the occurrence of dislocation movement.Another key area of research in this field involves the use of advanced modeling and simulation techniques to better understand the mechanisms of low-temperature creep. These approaches can help to identify which factors are mostcritical for material performance, and can guide thedevelopment of new materials and processing techniques thatare optimized for high-temperature applications.Overall, the development of advanced materials that are resistant to low-temperature creep is a critical goal for many high-tech industries. Efforts in this area will help to improve the efficiency and reliability of high-temperature applications, and will pave the way for new and innovative technologies in the years to come.In addition to the mechanical properties, the heat transfer properties of materials are also of great significance inhigh-temperature applications. Heat transfer refers to the process of transferring heat energy from one material to another. In high-temperature applications, materials areoften exposed to intense heat and thermal cycling, which can cause thermal stresses that lead to structural failure over time. Therefore, the design of high-temperature materialsmust consider the heat transfer properties of the material to ensure that it can withstand the extreme conditions.Another important aspect of developing advanced materials for high-temperature applications is the ability to withstand corrosion and oxidation. In the presence of high temperatures, materials are prone to undergo chemical reactions with the environment, leading to corrosion and oxidation that can weaken the material and ultimately cause structural failure. Therefore, designing materials that are resistant tocorrosion and oxidation is critical for ensuring thereliability and safety of high-temperature applications.Moreover, the development of advanced materials for high-temperature applications must also consider the cost-effectiveness of the materials. As high-temperature materials are often used in demanding applications that require high performance and durability, they can be expensive to produce. Therefore, designing cost-effective materials that offer high performance and reliability is also an important consideration in this field.In conclusion, the development of advanced materials that are resistant to low-temperature creep is a critical goal for many high-tech industries. The mechanical properties, heat transfer properties, corrosion resistance, and cost-effectiveness of these materials are all important considerations in the design and development process. Efforts in this area will help to improve the efficiency andreliability of high-temperature applications, and will pave the way for new and innovative technologies in the years to come.Advanced materials with the ability to resist low-temperature creep are vital for a variety of high-tech industries. These materials must possess excellent mechanical properties, heat transfer characteristics, and corrosion resistance, while remaining cost-effective. The development of these materials is crucial to improving the efficiency and reliability of high-temperature applications and enabling the development of new technologies.Low-temperature creep is a phenomenon in which a material deforms over time when subjected to stress at temperaturesbelow its melting point. This behavior can cause unwanted deformation in materials, leading to failure in high-temperature applications. In order to combat this, advanced materials that are resistant to low-temperature creep must be developed.One example of a material with excellent low-temperature creep resistance is tungsten. This material is known for its high melting point and exceptional mechanical properties, making it an ideal choice for high-temperature applications. Other materials that exhibit good low-temperature creep resistance include molybdenum, niobium, and tantalum.In order to improve the low-temperature creep resistance of these materials, various treatments and techniques can be used. For instance, the microstructure of the material can be modified using heat treatment or mechanical processing to improve its mechanical properties. Additionally, the addition of alloying elements can improve the mechanical and corrosion resistance properties of these materials.One of the key challenges in developing advanced materials with low-temperature creep resistance is cost-effectiveness. While materials such as tungsten and molybdenum offer excellent properties, they can be prohibitively expensive to use in large-scale applications. To address this, researchers are exploring the use of alternative materials, such as ceramics and composites, which can offer similar properties at a lower cost.In summary, the development of advanced materials with low-temperature creep resistance is critical to the success of many high-tech industries. These materials must possess excellent mechanical properties, heat transfer characteristics, and corrosion resistance while remaining cost-effective. While there are challenges associated with developing these materials, continued research and development will enable the design of more efficient and reliable high-temperature technologies in the future.To address the challenges of advanced materials with low-temperature creep resistance, researchers have explored various approaches such as alloy design, microstructural engineering, and surface modification. One promising strategy is to incorporate nanoscale strengthening features such as precipitates, grain boundaries, and dislocations into microstructures to hinder dislocation movement and enhance the mechanical strength and creep resistance.For example, researchers have developed a new generation of nickel-based superalloys with a high concentration of nanoscale gamma-prime (γ') precipitates, which significantly improve the creep resistance at high temperatures. The microstructure of these alloys consists of a solid solution phase and a dispersion of γ' precipitates. The stable γ' precipitate phase improves the strength and creep resistance by increasing the resistance to dislocation glide and preventing recrystallization at high temperatures.Another approach is to engineer the grain boundaries in metals and alloys to enhance the strength and ductility. Researchers have found that adding specific alloying elementssuch as magnesium, zirconium, and tantalum can improve the grain boundary strength and suppress the grain growth, which in turn enhances the low-temperature creep resistance of the materials. In addition, surface modification techniques, such as laser peening and shot peening, can induce compressive residual stresses on the material surface, which further enhances the mechanical properties and improves the fatigue and creep resistance.Moreover, advanced computational models and simulation tools have played a crucial role in predicting the mechanical properties and creep behavior of advanced materials at different temperatures and loading conditions. These models help researchers to design new materials with tailored properties and optimize the processing parameters to achieve the desired microstructure and mechanical performance.In conclusion, the development of advanced materials withlow-temperature creep resistance is essential for the success of high-tech industries such as aerospace, power generation, and electronics. The challenges associated with developing these materials are significant, but with continued research and development, we can design more efficient and reliable high-temperature technologies in the future. The integration of various approaches such as alloy design, microstructural engineering, and surface modification, along with advanced computational models, will pave the way for the development of next-generation materials with superior properties and performance.综上所述，高温材料的发展对于许多关键应用领域至关重要，包括能源、航空航天和电子。

高温合金材料的蠕变行为研究第一章引言高温合金材料一直在航空航天、能源等领域中扮演着重要的角色。

在高温环境下，材料的蠕变行为对于其性能和可靠性至关重要。

蠕变是指在高温和持续应力作用下材料具有可观的形变。

因此，对高温合金材料的蠕变行为进行深入的研究具有重要的意义。

第二章高温合金材料高温合金材料是一类能够在高温环境下保持良好性能的材料。

其主要成分包括基体和强化相。

基体通常由镍、铁或钴合金组成，而强化相则由钛、铝、铌等元素的沉淀相构成。

这些合金具有良好的热稳定性、抗氧化性和高温强度，因此在高温环境下广泛应用。

第三章蠕变行为的影响因素高温合金材料的蠕变行为受多种因素的影响。

其中最重要的因素包括温度、应力、时间和氧化环境。

高温下，材料的晶格结构发生变化，晶界开始扩散，导致材料的蠕变。

应力是引起蠕变的驱动力，而时间则决定了蠕变速率的快慢。

此外，氧化环境会加速材料的蠕变速率。

第四章蠕变机制高温合金材料的蠕变机制主要包括塑性蠕变和破断蠕变。

塑性蠕变是由于材料的滑移和晶界扩散引起的，主要表现为晶粒的变形和材料的形变。

破断蠕变是由于材料内部的细小孔洞或含氧化物颗粒的裂纹导致的材料断裂。

第五章蠕变行为测试方法为了研究高温合金材料的蠕变行为，需要进行一系列的测试。

常用的测试方法包括蠕变试验、压缩试验和扭转试验。

蠕变试验是最常用的方法，通过施加一定的应力和温度，观察材料的蠕变变形和断裂行为。

压缩试验和扭转试验主要用于评估材料的力学性能。

第六章蠕变行为模型为了更好地解释高温合金材料的蠕变行为，人们提出了多种蠕变行为模型。

其中最常用的是改变型蠕变模型和阻滞型蠕变模型。

改变型蠕变模型假设材料的蠕变是由于晶界滑移引起的，而阻滞型蠕变模型则假设材料的蠕变是由于晶粒内的障碍物引起的。

第七章蠕变行为的应用高温合金材料的蠕变行为研究对于材料的设计和应用具有重要的意义。

了解材料的蠕变行为可以帮助设计出更加耐高温环境的材料，提高材料的性能和可靠性。

镍基单晶高温合金在不同条件下的蠕变性能和组织演化史振学;李嘉荣;刘世忠;王效光【期刊名称】《中国有色金属学报（英文版）》【年(卷),期】2014(000)008【摘要】研究[001]取向的镍基单晶高温合金在不同测试条件下的蠕变性能，采用扫描电镜和透射电镜研究合金蠕变断裂后的γ′相、TCP相和位错组织演化特征。

结果表明：合金具有良好的蠕变性能，蠕变曲线显示出两种不同的蠕变变形特征。

在(760°C,600 MPa)、(850°C,550 MPa)条件下，蠕变第一阶段较长;在(980°C,250 MPa)、(1070°C,140 MPa)和(1100°C,120 MPa)条件下，蠕变第一阶段很短。

蠕变断裂后，在(760°C,600 MPa)条件下γ′相形态变化不大;在(850°C,550 MPa)条件下γ′相已经合并长大;在(980°C,250 MPa)条件下基体γ被γ′相包围;在(1070°C,140 MPa)条件下基体γ不再连续;在(1100°C,120 MPa)条件下基体γ厚度进一步增加。

在(760°C,600 MPa)、(850°C,550 MPa)和(980°C,250 MPa)条件下合金无TCP相析出，而在(1070°C,140 MPa)和(1100°C,120 MPa)条件下有针状TCP相析出。

在低温高应力下，变形特征为位错包括层错的剪切机制;在高温低应力下为位错绕过机制，并在γ/γ′相界面形成位错网。

%The creep properties of nickel-based single crystal superalloy with [001] orientation was investigated at different test conditions. The microst ructure evolution of γ′ phase, TCP phase and dislocation characteristic after creep rupture was studied by SEM and TEM. The results show that the alloy has excellent creep properties. Two different types of creep behavior can be shown in the creep curves. The primary creep ischaracterized by the high amplitude at test conditions of (760 °C, 600 MPa) and (850 °C, 550 MPa) and the primary creep strain is limited at (980 °C, 250 MPa), (1100 °C, 140 MPa) and (1120 °C, 120 MPa). A little changeofγ′precipitate morphology occurs at (760 °C, 600 MPa). The lateral merging of the γ′ precipitate has already begun at (850 °C, 550 MPa).Theγphase is surrounded by theγ′phase at (980 °C, 250 MPa). Theγphase is no longer continuous tested at (1070 °C, 140 MPa). At (1100 °C, 120 MPa), the thickness ofγphase continues to increase. No TCP phase precipitates in the specimens at (760 °C, 600 MPa), (850 °C, 550 MPa) and (980 °C, 250 MPa). Needle shaped TCP phase precipitates in the specimens tested at (1070 °C, 140 MPa) and (1100 °C, 120 MPa). The dislocation shear mechanism including stacking fault formation is operative at lower temperature and high stress. The dislocation by-passing mechanism occurs to form networks atγ/γ′interface under the condition of high temperature and lower stress.【总页数】8页(P2535-2542)【作者】史振学;李嘉荣;刘世忠;王效光【作者单位】北京航空材料研究院先进高温结构材料重点实验室，北京 100095;北京航空材料研究院先进高温结构材料重点实验室，北京 100095;北京航空材料研究院先进高温结构材料重点实验室，北京 100095;北京航空材料研究院先进高温结构材料重点实验室，北京 100095【正文语种】中文因版权原因，仅展示原文概要，查看原文内容请购买。

热暴露下预应变对CMSX-4单晶高温合金的显微组织演变的影响B. G. CHOI;C. Y. JO;H. U. HONG;I. S. KIM;S. M. SEO;H. M. KIM【摘要】在室温下,对经完全热处理的第二代单晶高温合金CMSX-4实施压缩和拉伸预应变.压缩和拉伸预应变在单晶CMSX-4中产生了剪切带.单晶CMSX-4在950℃下热暴露10h,沿剪切带产生了γ'粒子择优粗化.剪切带上的γ'粒子逐渐侵入γ通道.最后,γ通道沿着剪切带消失.TCP状粒子伴随着γ通道的消失而出现.然而,热暴露10 h的普通单晶CMSX-4没有产生TCP沉淀,也没有γ'粒子择优粗化.热暴露100 h的预应变CMSX-4沿剪切带产生了γ'粒子和TCP相粒子择优粗化,基体中也有γ'粒子粗化.【期刊名称】《中国有色金属学报（英文版）》【年(卷),期】2011(000)006【总页数】6页(P1291-1296)【关键词】预应变;显微组织演变;高温合金;CMSX-4【作者】B. G. CHOI;C. Y. JO;H. U. HONG;I. S. KIM;S. M. SEO;H. M. KIM【作者单位】High Temperature Materials Group, Korea Institute of Materials Science, 797 Changwondaero, Changwon 641-010, Korea;High Temperature Materials Group, Korea Institute of Materials Science, 797 Changwondaero, Changwon 641-010, Korea;High Temperature Materials Group, Korea Institute of Materials Science, 797 Changwondaero,Changwon 641-010, Korea;High Temperature Materials Group, Korea Institute of Materials Science, 797 Changwondaero, Changwon 641-010, Korea;High Temperature Materials Group, Korea Institute of Materials Science, 797 Changwondaero, Changwon 641-010, Korea;High Temperature Materials Group, Korea Institute of Materials Science, 797 Changwondaero, Changwon 641-010, Korea【正文语种】中文With the rapid development of automobile industry,advanced manufacturing technologies make automobile production to develop tothe direction of high-quality,high efficiency, low consumption and cleanness.The application of magnesium alloy in automobiles can play an important role in reducing the emission and conserving the energy resources.At present, one of the urgent problems to be resolved in the applications of magnesium alloy is to improve its strength to enable to apply to structural parts with requirement of high strength.However, magnesium alloy products are mainly castings, among which more than 90% are die castings,while magnesium alloy forgings with high-performanceare rarely applied[1-3].The main reason is because magnesium alloy is difficult to be forged due to its low plasticity.The high-cost production limits the application and development of high-performance magnesium alloy forgings to some extent.One of the differences between magnesium alloy and other materials such as aluminum alloy lies in the fact that magnesium cannot be forged toomany times,because the strength will decrease with the time increasing of heating and forging, especially when the heating temperature before forging is high and the time of reserving is long.Therefore, the time of forging for magnesium alloy in the process of forging compression should be controlled as short as possible[4].Extrusion perform closed molding forming process is a new near/net-shape technology developed based on the principles of plastic forming of magnesium alloy.On this basis, this work concerns the evolution of microstructure and texture of magnesium alloy during close net-shape pressing of extruded perform AZ61 magnesium alloy by using the technology of EBSD.The alloy used in the present study was AZ61 Mg alloy with the chemical composition listed in Table1.The alloy was supplied in the form of semi-continuouscast ingot with geometry of d 112 mm×250 mm.The ingot was homogenized at 385 ˚C for 12 h, and then extruded by the XJ-800T horizontal extruder for the profiles, with the parameters of temperature 385 ˚C,holding time 4 h, extrusion ratio 32 and extrusion speed 13-17 mm/s.The samples with a gauge geometry of 99.6 mm×9.0 mm for pressing were sectioned from the profiles by wire electric discharge machine, then were heated to the temperature of 400 ˚C in an electric resistance furnace for 12 min.As the self-made die was preheated to the same temperature, the pressing process can be carried out on 200 t forging machine.The pressing direction is perpendicular to the section at the speed of 5-17 mm/s with deformation rates of 10%, 30%,50%, 60%, respectively.The pressed samples were then air cooled and trimmed.Theschematic diagram of the processes is shown in Fig.1.The metallographic specimens of as-cast and heat treated states were sectioned from the billet at R/2 of its central line.They were firstly ground by abrasive papers,mechanically polished and chemically etched for 5-30 s using the solution of picric acid (3 g)+acetic acid (20 mL)+C2H5OH(50 mL) H2O (20 mL).The microstructure was observed by optical microscopy (OM).The specimens as-extruded and as-die pressed with different rates were sectioned as shown in Fig.2, then ground and electropolished for EBSD test in the material testing centre at Chongqing University.The microstructures of as-cast and solution treated at 400 ˚C AZ61 are represented in Figs.3(a) and (b)respectively.The as-cast AZ61 is character ized by α-Mg and intermetallic network phase β-Mg17Al12 distributed along the grain boundaries, which is produced by divorced eutectic phase.Such microstructure is typical in as-cast Mg-Al series, marked by image analysis as secondary dendrite arm with spacing of 35 µm.In Fig.3(b) uniform single phase is presented due to β-phase remelting into α-Mg after solution treatment at 400 ˚C for 12 h, and its average grain size are 110 µm.The microstructures of as-extruded AZ61 and as-die pressed with different rates are shown in Fig.4.It can be seen from Fig.4(a) that significant dynamic recrystallization(DRX) takes place during extrusion process, and coarse grain is replaced by finer equiaxed grain with average size of 3.5 µm.When the as-extruded sample is pressed in the die at 400 ˚C with deformation rate 10%, the average size of finer equiaxed grain tends to increase to 6µm.DRX is almost completed as the deformation rateincreases, and the recrystallized grains are distributed parallel to the pressing direction and rotated along the boundaries.When the deformation rate is within 30%,the average grain size is 2-3 µm, whereas the rate reaches 50%-60%, the grain size is decreased to 1-2.5µm, and the recrystallized grains of AZ61 magnesium alloy are elongated or crushed and present on “S”streamlines, as shown in Fig.5.At a certain deformation temperature and small deformation degree, distrotional energy of metal material is relatively small even without enough recrystallization energy, so the grain size of alloy does not change obviously, while the deformation rates arrive at a certain value (2%-10%)[5], the grain size tends to increase with small deformation rate (10%) under 400˚C.The average recrystallized grain size can be expressed byd=K(G/N)1/4, where G is the linear velocity of growth, N is the nucleation rate, K is the proportional factor.The recrystallized grain size is determined by the ratio of G/N.The ratio of G/N is relatively small with small deformation rate, so the deformation rate of AZ61 alloy is 10%, which grows up apparently.With increasing deformation rate, distrotional energy of metal material raises too, G and N increase at the same time, but the increment rate of N is greater than the increment rate of G, which resultsin the rate of G/N reduce and grain size is refined, while deformation rate reaches up to 50%-60%, the increment rate of N and increment rate of G are basically analogous and the recrystallized grain size of alloys basically tends to be stable.Texture and grain orientation of AZ61 magnesium alloy during as-extruded and as-die pressing of extruded preformed with different rates are illustrated in Figs.6(a)-(b).Grain boundary sliding has little influence on grain orientation, and texture formation is caused by intracrystalline plastic slip.Generally, the deformation during hot processing is also caused by texture, and various types of texture represent different deformation mechanisms[6].Studies[7-11] have shown that a strong basal texture (0001) is formed as a result of basal slip and pyramidal twinning in magnesium alloys during rolling.Fig.6(a) is characterized by initial texture formed in extruded preforming, and the initial orientation is at basal texture {0001}<100> located in the centre of pole figure (Y0), while the basal texture is symmetrical and parallel to extrusion direction (ED), whereas minute quantity of grains is along prismatic plane (10)parallel to ED, and the maximum texture intensity is 15.37 and the peak value of misorientation of grain is 28˚-38˚.Texture and grain or ientation vary significantly with deformation rate increment, whereas texture intensity decreases.It can be seen from Figs.6(b)-(c) that basal texture {0001}<10> of initial orientation deviates from Y0 with a certain angle, and texture intensity is 5.48, 6.84, 9.62, 9.30 respectively.Themaximum texture intensity can be obtained when deformation rate of pressing reaches up to 50%, and further deformation leads to texture intensity decrease.The deformation texture mechanism of magnesium alloys is caused by grain rotation under external stress,and differs as stress changes.In the extrusion process, the state of plane stress is tensile in extrusiondirection(ED) and compressed in normal direction (ND), and the initial basal texture{0001}<100> is parallel to ED, as shown in Fig.7(a).Initial deformation for specimens in hot pressing process of AZ61 is similar to uniaxial compression, and only transverse deformation takes place, whereas longitudinal size remains the same.Further deformation leads to metallic flow in transverse direction under three-dimensional compressive stress. Because width/height ratio is 4, deformation instability occurred in initial pressing, and the shear stress incurs irregular metallic flow, which is illustrated in Ⅱ and Ⅲ zones in Fig.5.Meanwhile, the shear stress also leads to grain rotation along boundaries with certain angles, and basal texture and grain orientation are easily perceived with increasing deformation.The strong basal fiber texture formed during extrusion gives rise to weak basal texture intensity at the beginning of pressing process, so the basal slip and pyramidal twinning cannot effort under normal compressive stress. Therefore, further deformation can be easily conducted, which, in contrast,leads to fiber texture[12]intensified.Simultaneously, the basal preferential orientation deviates from extrusion direction and aligns with the main pressing and deformation direction under three-dimensional compressive stress, as shown inFig.7(b).1) The average size of as-extruded grain is 3.5 µm,while the grain afterhot-pressing is significantly refined.And the average size of grains is 6 µm which tends to increase with small deformation.As deformation rate is 30%, the average size of grains is 2-3 µm, whereas the def ormation rate reachesup to 50%-60%, the size is decreased to 1-2.5 µm and tends to be stable, but grain refined are not obvious.2) The profiles of extruded preforming is dominantly on basal texture {0001}<10>, and the basal plane is parallel to extrusion direction (ED).As deformation continues, the inner shear stress gives rise to grain rotation along boundaries with certain angles and initial basal texture and grain orientation vary remarkably,though the texture intensity is weaker than that as-extruded.The basal preferential orientation deviates from extrusion direction and aligns with the pressing direction.【相关文献】[1] KANG H T, OSTROM T.Mechanical behavior of cast and forged magnesium alloys and their microstructures [J].Materials Science and Engineering A, 2008, 49(1/2): 52-56.[2] GUAN S K, WU L H, WANG P.Hot forgeability and die-forging forming of semi-continuous casting AZ70 Mg-alloy [J].Materials Science and Engineering A, 2009, 499(1/2): 187-191.[3] WU Li-hong, GUAN Shao-kang, WANG Li-guo, LIU Jun.Wrought magnesium alloys and several key factors affecting the forging forming [J].Forging Technology.2006, 31(4): 7-10.(in Chinese)[4] LONG Si-yuan, CAO Feng-hong, LIAO Hui-min.A compound forming method of magnesium 200810069225.7[P].2008-01-10.[5] CUI Zhong-qi.Metallurgy and heat treatment [M].2006: 1.[6] YANG Ping, REN Xue-ping, ZHAO Zu-de.Microstructures and textures in hot deformed and annealed AZ31 magnesium alloy [J].Transactions of Materials and Heat Treatment, 2003, 12(4): 12-17.(in Chinese)[7] MYAGCHILOV S, DAWSON P R.Evolution of texture in aggregates of crystals exhibiting both slip and twinning [J].Modelling and Simulation in Materials Science and Engineering,1999, 7: 975-1004.[8] WAGNER L, HILPERT M, WENDT J.On methods for improving the fatigue performance of the wrought magnesium alloys AZ31 and AZ80 [J].Materials Science Forum, 2003,419/422: 93-102.[9] KALIDINDI S R.Modeling anisotropic strain hardening and deformation textures in low stacking fault energy materials [J].International Journal of Plasticity, 2001, 17: 837-860. [10] CHRISTIANJ W, MAHAJAN S.Deformation twinning [J].Progress in Materials Science, 1995, 39: 1-157.[11] POSS R.Sheet metal production of magnesium [J].Materials Science Forum, 2003, 419/422: 327-336.[12] VALLE J A, PRADO M T, RUANO O A.Texture evolution during large strain hot rolling of the AZ61 Mg alloy [J].Materials Science and Engineering A, 2003, 355: 68-78.。

CMSX-4单晶高温合金TLP接头组织与性能王瑶;唐新华;崔海超【摘要】采用含Si的BNi-5非晶箔片作为中间层合金对CMSX-4镍基单晶合金棒在放电等离子体烧结炉中进行TLP连接,采用SEM观测了TLP接头在不组织形貌特征,借助于EDS分析了TLP接头界面处的物相组成及其对接头力学性能的影响.采用常温和高温拉伸试验验证了不同焊接工艺条件对TLP接头性能的影响.结果表明,在1 200℃/5 kN/20 min工艺参数下可得到满意的TLP接头,此时组织分布较为均匀,常温抗拉强度达到了母材的95％,760℃高温抗拉强度达到母材的99％.【期刊名称】《焊接》【年(卷),期】2018(000)003【总页数】6页(P24-29)【关键词】瞬间液相扩散焊;CMSX4;镍基单晶高温合金;接头组织;力学性能【作者】王瑶;唐新华;崔海超【作者单位】上海交通大学材料科学与工程学院上海市激光制造与材料表面改性重点实验室,上海200240;高新船舶与深海开发装备协同创新中心,上海200240;上海交通大学材料科学与工程学院上海市激光制造与材料表面改性重点实验室,上海200240;高新船舶与深海开发装备协同创新中心,上海200240;上海交通大学材料科学与工程学院上海市激光制造与材料表面改性重点实验室,上海200240;高新船舶与深海开发装备协同创新中心,上海200240【正文语种】中文【中图分类】TG4540 前言镍基高温合金具有优良的高温性能，近年来广泛用于商业航空燃气喷气发动机涡轮叶片中[1]。

CMSX-4是第二代镍基单晶高温合金，是在第一代CMSX系列单晶的基础上大幅度添加了难熔元素Re，显微组织主要由γ′相和γ相组成。

由于发动机涡轮叶片具有复杂的型腔结构，单凭铸造技术难以实现整体制造，需采用连接技术。

绝大多数高温合金用熔焊的方法连接极易产生熔焊裂纹[2]。

例如，用钨极氩弧焊连接CMSX-4单晶，焊接接头会出现凝固裂纹[3]。

涡轮叶片材料CMSX-4超温状态组织演变研究
彭霜;石凤仙;滕跃飞;孙智君;曹玮
【期刊名称】《失效分析与预防》
【年(卷),期】2024(19)2
【摘要】以涡轮叶片用材料CMSX-4合金为研究对象,采用体式显微镜、扫描电镜、维氏硬度计等研究了CMSX-4合金在超温状态下的组织演变以及硬度变化。

结果
表明:随温度升高,γ′相长大聚集的同时伴随着γ′相回溶,γ′相立方度下降,γ通道变宽。

当超温处理温度到达1250℃时,γ/γ′相界面呈锯齿状;当温度达到1300℃后,γ′相全部回溶;当温度达到1350℃时,合金开始初熔,出现大量孔洞与γ+γ′共晶。

当在1300℃以下一定温度保温时,随着保温时间的延长,γ′相百分含量逐渐减少并趋于稳定。

当温度达到γ′相全部回溶温度时,因重新析出细小的二次γ′相,合金硬度显著升高,最高硬度达458 HV,比原始状态提高约12%。

因此,对于过热等异常服役引起组织损伤与退化,可结合叶片宏观形貌、γ′相形态与百分含量、硬度退化情况进行材
料损伤程度的评估。

【总页数】10页(P99-108)
【作者】彭霜;石凤仙;滕跃飞;孙智君;曹玮
【作者单位】中国航发商用航空发动机有限责任公司
【正文语种】中文
【中图分类】TG132.3
【相关文献】
1.基于某航空发动机振动事件的高压涡轮转子叶片超温问题研究
2.超超临界汽轮相高温叶片用11Cr-Co-W-Mo-V-Nb-N-B-材料的热处理工艺与组织相分析试验研究
3.热暴露下预应变对CMSX-4单晶高温合金的显微组织演变的影响
4.基于显微组织演变的涡轮叶片损伤分析
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镍基单晶高温合金力学性能各向异性的研究进展窦学铮;蒋立武;宋尽霞;赵云松【期刊名称】《材料导报》【年(卷),期】2022(36)24【摘要】镍基单晶高温合金凭借优良的高温力学性能和组织稳定性而成为目前制造先进航空发动机和燃气轮机叶片的主要材料,其力学性能各向异性对涡轮叶片的服役性能和安全可靠性至关重要,受到叶片设计师和制造专家的高度重视。

为了满足更严苛的使用要求,国内外都在不断研发新型的镍基单晶高温合金来提升叶片承温能力,但是对新型合金力学性能各向异性的研究还不是很全面,对新添加元素的作用机理也有待进一步的研究。

近些年来,国内外相关研究表明,镍基单晶高温合金力学性能各向异性与温度、应力等因素有关,不同的单晶合金表现出不同的规律。

镍基单晶高温合金的拉伸性能具有明显的各向异性,随着温度的升高,其原子扩散能力增强,开动滑移系的数量增多,拉伸性能的各向异性减弱。

随着合金成分中难熔元素含量的增加,滑移系的位错交截概率或变形协调性发生变化,合金表现出不同的拉伸性能各向异性。

在中温高应力条件下,合金蠕变性能存在显著的各向异性。

随着应力的升高,[001]取向的蠕变性能显著降低,[111]取向变化较小,这与应力变化对滑移系数量的影响有关。

随着难熔元素含量的增加,合金不同取向滑移系的开动和层错的形成更容易,从而影响蠕变性能的各向异性。

在高温低应力条件下,[111]取向蠕变性能较好,[001]和[011]取向较差,但蠕变各向异性减弱。

低周疲劳性能也具有明显的各向异性,[001]取向的疲劳寿命最长,[011]取向次之,[111]取向最短;而高周疲劳性能按[111]、[001]、[011]取向的顺序依次降低,主要与弹性模量、滑移系开动的数量和Schmid因子等因素有关。

本文详细介绍了镍基单晶高温合金拉伸、蠕变、疲劳等力学性能各向异性的研究进展,揭示了不同晶体取向合金的失效机理,分析了新型镍基单晶高温合金力学性能各向异性相关研究存在的问题并展望其前景,以期为未来镍基单晶高温合金在航空发动机涡轮叶片上的应用提供有益参考。