Researchonflowstresso_省略_ompressiondefor

  • 格式:pdf
  • 大小:225.50 KB
  • 文档页数:6
exp(Q / RT ) Z =ε
(2)
Some researches indicated that Z and σ satisfy a particular relationship [7-8]:
Z = A1[sinh(ασ )] n
(3)
There is an equation deduced from Eqs. (2) and (3):
= A[sinh(ασ )] n exp(−Q / RT ) ε
(4)
Eq. (4) is an ameliorated Arrhenius equation that
Wei Y.G. et al., Research on flow stress of spray formed 70Si30Al alloy under hot compression…
RARE METALS Vol. 25, No. 6, Dec 2006, p. 665
Research on flow stress of spray formed 70Si30Al alloy under hot compression deformation
WEI Yanguang, XIONG Baiqing, ZHANG Yong’an, LIU Hongwei, ZHU Baohong, and WANG feng
rapidly to its maximum, and then decreases rapidly and subsequently remains constant.
Fig. 1. Variations in true stress of spray formed 70Si30Al alloy at different temperatures at a strain rate of 0.01: (a) 923 K; (b) 953 K; (c) 993 K; (d) 1033 K.
2. Experimental
The experiment was conducted on a Gleeble-1500 testing machine. Specimens used in this
Corresponding author: WEI Yanguang
E-mail: weiygand Tegart, and the equation is in a hyperbolic sinusoidal format including Q and T. Many researches indicated that the equation
spray formed 70Si30Al alloy at strain rates of 0.01, 0. 1 and 1, respectively. Zener and Hollom expounded and demonstrated a relationship of σ and ε by a tensile experiment of steel in 1994 [6]: σ = σ (Z , ε ) (1)
666
RARE METALS, Vol. 25, No. 6, Dec 2006
and then increases gradually to its maximum and subsequently decreases rapidly and remains constant. When the strain rate is 1, the flow stress increases
State Key Laboratory for Fabrication & Processing of Non-ferrous Metals, Beijing General Research Institute for Non-ferrous Metals, Beijing 100088, China (Received 2005-08-23)
Abstract: The flow stress of spray formed 70Si30Al alloy was studied by hot compression on a Gleeble-1500 test machine. The experimental results indicated that the flow stress depends on the strain rate and the deformation temperature. The flow stress increases with an increase in strain rate at a given deformation temperature. The flow stress decreases with the deformation temperature increasing at a given strain rate. The relational expression among the flow stress, the strain rate, and the deformation temperature satisfies the Arrhenius equation. The deformation activation energy of 70Si30Al alloy during hot deformation is 866.27 kJ/mol from the Arrhenius equation. Key word: 70Si30Al alloy; spray forming; flow stress; hot compression; Arrhenius equation
3. Results and discussion
3.1. Relationship between true stress and true strain of spray formed 70Si30Al According to the increase of deformation temperature at strain rates of 0.01, 0.1 and 1, Figs. 1-3 show the true stress-strain curves. It can be found that the deformation behavior of 70Si30Al alloy is sensitive to strain rate. When the strain rate is 0.01, the flow stress increases rapidly, which has elastic deformation stage, and then increases gradually to its maximum and subsequently decreases to some extent or approximately remains constant. When the strain rate is 0.1, the flow stress increases rapidly,
could explain the laws of conventional deformation better [9-11].
experiment were cut and machined from a spray formed 70Si30Al preform to the size of 12 mm in diameter and 15 mm in length. Specimens were heated at a rate of 10 K/s and then held at a test temperature of 923 K, 953 K, 993 K or 1033 K for 3 min, and subsequently compressed at a strain rate of 0.01, 0.1 or 1 until the materials fractured completely.
From Figs. 1-3, it could be observed that the peak stress and average value of the steady-state stress decrease with the increasing of deformation temperature at a given strain rate, because the solid fraction and resistance of deformation decrease with an increase in deformation temperature. However, the peak stress and average value of the steady state stress increase with an increase in strain rate at a given deformation temperature. In other words, the flow stress increases with the increase of strain rate. 3.2. Flow stress equation There is a particular relationship among the flow stress, the strain rate, and the deformation temperature by the analysis of true stress-strain curves of
[This work was financially supported by the National Basic Research Program of China (No. G20000672).]