(1. 大连理工大学 材料科学与工程学院, 大连 116024;
2. 大连理工大学 工业装备结构分析国家重点实验室, 大连 116024)
摘 要: 在600 ℃和较低应变速率下进行NiTi 合金的拉伸实验, 研究了拉伸过程中外加电场（E=1 kV/cm）对其高温变形行为的影响。 采用金相显微镜和扫描电镜对材料的微观组织进行分析。 结果表明： 外加电场可有效降低NiTi合金的屈服强度和塑性变形的流动应力, 提高断裂延伸率； 同时外加电场有效地抑制了NiTi 合金在塑性变形过程中空洞的形成。 在600 ℃, 2.6×10-2 s-1下, 不加电场进行拉伸, 得到应力—应变曲线的周期性波浪曲线, 而在同样条件下施加电场时, 动态再结晶与应变硬化同时发生, 形成稳态的流动曲线。 研究认为, 施加电场促进了NiTi合金高温塑性变形时的位错运动。
关键字: NiTi合金； 直流电场； 高温变形； 应力—应变曲线
NiTi alloys in DC electric field
（1. School of Materials Science and Engineering,
Dalian University of Technology, Dalian 116024, China;
2. National Key Laboratory of Structural Analysis for Industrial Equipment,
Dalian University of Technology, Dalian 116024, China）
Abstract: The effects of a DC electric field up to 1kV/cm on the deformation behavior of NiTi alloys were determined at constant strain rate of 2.6×10-2 s-1 and temperature of 600 ℃. The microstructures were analyzed by metallomicroscopy and SEM. The results demonstrate that the application of electric field decreases the flow stress and the tensile strength and increases the tensile elongation. The existence of the electric field also suppresses the nucleation and growth of internal cavities in tension. When NiTi alloys are tensiled at 600 ℃, the dynamic recrystallization occurs. Without electric field, the stress-strain curves were characterized by periodical undee graph, while under the electric field the curves present steady state. When the deformation under the electric field, the strain hardening and recrystallization take place simultaneously, thus the flow stress curves exhibits steady state. Further analyses demonstrate that the applied electric field promotes the movement of the dislocations in elevated temperature tension.
Key words: NiTi alloys; DC electric field; high temperature deformation; stress—strain curve
