添加Cr对Ti-Ni形状记忆合金相变和低温形变特性的影响

用示差扫描量热仪和拉伸试验研究了添加Cr对形变退火态Ti-Ni形状记忆合金相变和低温形变特性的影响。结果表明,添加微量Cr后,Ti-Ni合金的R、马氏体(M)相变温度θR和θM大幅度降低,M相变热滞?θM增加,应力-应变曲线的平台应力σM显著提高,超弹性(SE)改善,塑性变差。添加微量Cr后,Ti-Ni合金的低温SE特性大幅改善。室温下,Ti-50.8Ni合金呈现形状记忆效应(SME)+SE,而Ti-50.8Ni-0.3Cr合金则呈现SE。退火温度也显著影响Ti-Ni合金的低温形变特性。在10℃变形时,400～500℃退火态Ti-50.8Ni合金呈现SME,550～650℃退火态Ti-50.8Ni合金呈现SME+SE,而400～650℃退火态Ti-50.8Ni-0.3Cr合金则持续呈现SE。

Effect of Adding Cr on Transformation and Low Temperature Deformation Characteristics in Ti-Ni Shape Memory Alloy

The effects of adding Cr on the transformation and the low temperature deformation characteristics in the deformed plus annealed Ti-Ni shape memory alloy(SMA) were investigated by differential scanning calorimetry and tensile test.The results show that after adding trace Cr,the R and martensite(M) transformation temperatures θR and θM decrease a lot,the M transformation temperature hysteresis ΔθM increases,the platform-stress σM in the stress-strain curves increases significantly,and the superelasticity(SE) improves,and the ductility deteriorates in Ti-Ni SMA.After adding trace Cr,the low-temperature SE of Ti-Ni SMA also improves greatly.At room temperature,the Ti-50.8Ni SMA shows shape memory effect(SME) + SE,while the Ti-50.8Ni-0.3Cr SMA shows SE.The annealing temperature affects low temperature deformation characteristics of Ti-Ni SMA.When deformed at 10 ℃,the 400-500 ℃ annealed Ti-50.8Ni SMA shows SME,the 550-650 ℃ annealed Ti-50.8Ni SMA shows SME + SE,while the 400-650 ℃ annealed Ti-50.8Ni-0.3Cr SMA shows SE continuously.