(1. 大連理工大學(xué) 材料科學(xué)與工程學(xué)院, 大連 116024;
2. 大連理工大學(xué) 工業(yè)裝備結(jié)構(gòu)分析國家重點實驗室, 大連 116024)
摘 要: 在600 ℃和較低應(yīng)變速率下進行NiTi 合金的拉伸實驗, 研究了拉伸過程中外加電場（E=1 kV/cm）對其高溫變形行為的影響。 采用金相顯微鏡和掃描電鏡對材料的微觀組織進行分析。 結(jié)果表明： 外加電場可有效降低NiTi合金的屈服強度和塑性變形的流動應(yīng)力, 提高斷裂延伸率； 同時外加電場有效地抑制了NiTi 合金在塑性變形過程中空洞的形成。 在600 ℃, 2.6×10-2 s-1下, 不加電場進行拉伸, 得到應(yīng)力—應(yīng)變曲線的周期性波浪曲線, 而在同樣條件下施加電場時, 動態(tài)再結(jié)晶與應(yīng)變硬化同時發(fā)生, 形成穩(wěn)態(tài)的流動曲線。 研究認(rèn)為, 施加電場促進了NiTi合金高溫塑性變形時的位錯運動。
關(guān)鍵字: NiTi合金； 直流電場； 高溫變形； 應(yīng)力—應(yīng)變曲線
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
