对两种晶粒尺寸的99.999％高纯Al试样,经充分退火后,在不同形变温度和不同应变速率下,进行小应变静拉伸试验,结果表明,提高温度和降低应变速率均有助于减小形变硬化。 使用光学显微镜和透射电子显微镜观察了形变后晶界及其邻近区域的状态,确定了温度及应变速率是控制晶界吸收、放出及阻碍位错运动的重要因素。并指出在小应变范性形变中,晶界与位错的交互作用机制是形变条件影响宏观力学性能的重要原因,晶粒尺寸是这一交互作用强度的度量。 本文推导了形变硬化系数A与变形温度、应变速率和晶粒尺寸之间的函数关系式,根据实验数据作了回归计算,求得晶界吸收位错的激活能为0.35eV。
Static tensile tests for 99.999%Al with two grain sizes were conducted with strain rates of 10~(-6) to 10~(-4)S~(-1) and temperatures of-150 to+250℃. The slip traces, the topography near the grain boundary on the surface of tensile specimens and the structure of dislocations were observed hy means of optical microscope and TEM. The results show that the strain hardening reduces with increase of temperature and decrease of strain rate, and it depends upon the interaction between grain boundaries and dislocations which are controlled by both temperature and strain rate. The hardening coefficient A as a function of deformation temperature T, strain rate e and grain size d was derived. (A/G)-T, (A/G)-ε and (A/G)-d curves were computed and compared with experimental data, where G is shear stress.
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