ECAP对纯铜循环硬化/软化特性的改变

以纯铜棒材试样为研究对象，通过试验研究不同道次等通道转角挤压（ECAP）后材料的单轴拉压循环行为，探讨ECAP后材料循环特性的变化，得到以下结论：（1）具有循环硬化特性的纯铜进行ECAP挤压后，其循环特性可转变为循环软化；（2）第一道次ECAP挤压对材料循环应力应变响应的强化作用最大，后续道次挤压对强化的效用迅速降低，4道次以后挤压的强化作用似可忽略不计；（3）因循环软化，纯铜经ECAP挤压后的循环应力应变曲线大大低于其单调拉伸应力应变曲线，与未经ECAP挤压的结果相反。本文研究表明，评估ECAP对材料的强化效果需同时考察材料单调加载和循环加载的力学性能。

From cyclic hardening to cyclic softening: transforming of an ECAPed copper

In order to realize the influence of the ECAP (equal channel angular pressing) to cyclic properties of a material, the bar material of pure copper after multi-pass ECAP is chosen as a study subject and its mechanical behavior under uniaxial tension-compression cycle is investigated by experiment. This research is focus on the change of cyclic behavior of the copper after ECAP. According to the results and observes the conclusions are obtained: (1) The copper treated by ECAP may lead to the transform of cyclic properties from cyclic hardening to cyclic softening; (2) The first pass ECAP has the greatest effect on strengthening of the stress-strain response, the effectiveness of subsequent pass of ECAP will reduce severely and it can be regardless of that for subsequent pass after 4; (3) It has great difference by comparing the stress-strain response between the copper original and ECAPed. The monotonic uniaxial tension stress-strain curve is much higher than the cyclic stress-strain curve for the ECAPed copper, but it is on the contrary for the copper in original state. So it is necessary to evaluate mechanical properties strengthening by ECAP from both the monotonic and cyclic conditions simultaneously.