Co对Ti-Ni形状记忆合金相变和形变特性的影响

Effect of Co on Transition and Deformation Characteristics of Ti-Ni Shape Memory Alloy

摘要:

用热重分析仪、X射线衍射仪、示差扫描量热仪及拉伸试验研究了Co对Ti-49.8Ni(at%, 下同)形状记忆合金相变和形变特性的影响。结果表明，中温退火态Ti-49.8Ni合金冷却/加热时的相变类型为A→R→M/M→A(A—母相，R—R相，M—马氏体相)；随退火温度升高，该合金的马氏体相变温度升高， R相变温度先升高后降低；该合金室温相组成为马氏体，具有形状记忆效应(SME)。用1%Co置换等量Ti后所得Ti-49.8Ni-1Co合金冷却/加热时的相变类型为A→R→M/M→R→A，相变温度低，室温组成相为母相A，具有超弹性(SE)特性。退火温度低于600 ℃时，Ti-Ni基合金的SME和SE特性良好，退火温度超过600 ℃后，合金氧化加剧，SME和SE特性变差，塑性显著提高

Abstract:

The effects of Co on the transition and the deformation characteristics of Ti-49.8Ni shape memory alloy were investigated by thermal gravity, X-ray diffraction, differential scanning calorimetry and tensile test. The results indicate that the phase transformation types of intermediate-temperature annealed Ti-49.8Ni alloy during cooling/heating cycle is A→R→M/M→A (A—parent phase, R—R phase, M—martensite phase). With the annealing temperature increasing, the M-phase transformation temperature of Ti-49.8Ni alloy increases, and the R-phase transition temperature increases first and then decreases. The phase of Ti-49.8Ni alloy at room temperature is martensite and shows shape memory effect (SME). After adding 1% Co, the transformation type of Ti-49.8Ni-1Co alloy is A→R→M/M→R→A upon cooling/heating, and the transition temperature of the alloy is low. The phase of Ti-49.8Ni-1Co alloy at room temperature is parent phase, and shows superelasticity (SE). The excellent SME and SE can be obtained in Ti-Ni base alloys when the annealing temperature is below 600 ℃. When the annealing temperature is over 600℃, the oxidation of Ti-Ni alloys speeds up, SME and SE become bad, but the plasticity of the alloy is improved significantly