退火温度对TiNi记忆合金马氏体相变超弹性能的影响

Effect of annealing temperature on superelastic properties of martensitic transformation of TiNi memory alloy

采用X射线衍射仪、差示扫描量热法、透射电镜和拉伸试验等研究了退火温度对拉拔变形后的TiNi记忆合金的微观组织、马氏体相变应力、回复应变、残余应变、吸收能量、储存能量及耗散能量的影响。结果表明:当退火温度由350℃升高至550℃,TiNi记忆合金的平均晶粒尺寸由15 nm增大至400 nm,马氏体相变应力由766 MPa降低至115 MPa,回复应变由6.7%减小至0.8%,残余应变由1.3%增大至7.2%,马氏体相变的吸收能量由50.6 MJ/m^(3)减小至8.6 MJ/m^(3),马氏体相变的储存能量由15.7 MJ/m^(3)减小至0.8 MJ/m^(3),马氏体相变的耗散能量由34.9 MJ/m^(3)减小至8.0 MJ/m^(3)。分析认为退火温度对上述TiNi记忆合金马氏体相变超弹性能的影响主要是因为随着退火温度的升高,TiNi记忆合金的晶粒尺寸增大,晶界密度降低,由此降低了合金应力诱发马氏体相变的阻力,进而影响其超弹性能。

Effect of annealing temperature on microstructure,martensitic transformation stress,recovery strain,residual strain,absorbed energy,stored energy and dissipation energy of TiNi memory alloy after drawing deformation was studied by means of X-ray diffraction,differential scanning calorimetry,transmission electron microscopy and tensile test.The results show that when the annealing temperature increases from^(3)50℃to 550℃,the average grain size of the TiNi memory alloy increases from 15 nm to 400 nm,the martensitic transformation stress decreases from 766 MPa to 115 MPa,the recovery strain decreases from 6.7%to 0.8%,the residual strain increases from 1.3%to 7.2%,the absorbed energy of martensitic transformation decreases from 50.6 MJ/m^(3) to 8.6 MJ/m^(3),the stored energy of martensitic transformation decreases from 15.7 MJ/m^(3) to 0.8 MJ/m^(3),and the dissipation energy of martensitic transformation decreases from^(3)4.9 MJ/m^(3) to 8.0 MJ/m^(3).The analysis suggests that the influence of annealing temperature on the martensitic transformation superelasticity performance of the TiNi memory alloy mentioned above is mainly due to the increase in annealing temperature,which increases the grain size of the TiNi memory alloy and reduces the density of grain boundaries,thereby reducing the resistance of alloy stress induced martensitic transformation and affecting its superelasticity performance.