Low-temperature superplasticity of ultra-fine-grained Ti-6Al-4V processed by equal-channel angular pressing
Low-temperature superplasticity of ultra-fine-grained Ti-6Al-4V processed by equal-channel angular pressing
复制标题
DOI：
10.1007/s11661-006-0008-z
复制
发表时间：
2006-02-01
影响因子：
2.8
通讯作者：
Semiatin, SL
中科院分区：
文献类型：
--
作者：
Ko, YG;Lee, CS;Semiatin, SL
研究了超细晶Ti-6Al-4V合金的低温超塑性随温度和应变速率的变化规律。通过在873 K下等温等通道角挤压（ECAP）施加近似于4的有效应变，将起始材料的等轴α晶粒尺寸从11 μ m减小到0.3 μ m（体积分数没有变化）。在873 K以下的退火过程中，所得到的超细显微结构相对稳定.在873 ~ 973 K的温度和5 × 10（-5）~ 10（-2）s（-1）的应变速率下，对初始（粗晶（CG））和UFG材料进行了单轴拉伸和载荷松弛试验。拉伸试验表明，在相同的温度和应变速率下，UFG结构表现出相当高的伸长率相比，CG试样。在973 K和10（-4）s（-1）条件下，UFG合金的总延伸率为474%。这一事实有力地表明，低温超塑性可以实现使用UFG结构，通过除了应变硬化的晶界滑动的增强。通过载荷松弛试验和基于非弹性变形理论的解释，阐明了超细晶Ti-6Al-4V低温超塑性的变形机制。
The low-temperature superplasticity of ultra-fine-grained (UFG) Ti-6Al-4V was established as a function of temperature and strain rate. The equiaxed-alpha grain size of the starting material was reduced from 11 to 0.3 mu m (without a change in volume fraction) by imposing an effective strain of similar to 4 via isothermal, equal-channel angular pressing (ECAP) at 873 K. The ultrafine microstructure so produced was relatively stable during annealing at temperatures up to 873 K. Uniaxial tension and load-relaxation tests were conducted for both the starting (coarse-grained (CG)) and UFG materials at temperatures of 873 to 973 K and strain rates of 5 X 10(-5) to 10(-2) s(-1). The tension tests revealed that the UFG structure exhibited considerably higher elongations compared to those of the CG specimens at the same temperature and strain rate. A total elongation of 474 pct was obtained for the UFG alloy at 973 K and 10(-4) s(-1). This fact strongly indicated that low-temperature superplasticity could be achieved using an UFG structure through an enhancement of grain-boundary sliding in addition to strain hardening. The deformation mechanisms underlying the low-temperature superplasticity of UFG Ti-6Al-4V were also elucidated by the load-relaxation tests and accompanying interpretation based on inelastic deformation theory.