Ti-50.8Ni合金的相变、形状记忆和超弹性特性

Transformation, Shape Memory and Superelasticity Characteristics of Ti-50.8Ni Alloy

摘要:

用热重分析仪、X射线衍射仪、光学显微镜、示差扫描热分析仪和拉伸试验研究了Ti-50.8Ni形状记忆合金的组织、相变、形状记忆效应（SME）和超弹性（SE）特性。结果表明，Ti-50.8Ni合金在600 ℃以下退火后组织呈纤维状，在该温度以上退火后组织呈等轴状。加热温度超过600 ℃后合金氧化加剧。随退火温度Ta升高，合金冷却/加热过程中的相变类型由A→R→M/M→R→A型向A→R→M/M→A型再向A→R/R→A型转变（A—奥氏体，R—R相，M—马氏体），合金的M相变温度升高，R相变温度降低，M相变热滞降低，合金室温特性由SME+SE向SE转变。形变温度Td＜20 ℃时，合金弹簧呈SME+SE，Td＞30 ℃时，合金弹簧呈SE。随Td升高，合金弹簧的应力诱发M应力升高。

Abstract:

The microstructure, transformation, shape memory effect (SME) and superelasticity (SE) characteristics of Ti-50.8Ni shape memory alloy were investigated by thermal gravimetry, X-ray diffraction, optical microscopy, differential scanning calorimetry and tensile testing. The results show that the microstructure of Ti-50.8Ni alloy is fibrous after annealing below 600 oC, while it is equiaxed after annealing over 600 oC. The alloy oxidation speeds up when the heating temperature is over 600 oC. With the annealing temperature Ta increasing, the transformation types of Ti-50.8Ni alloy change from A→R→M/M→R→A to A→R→M/M→A to A→R/R→A (A—parent phase, R—R phase, M—martensite), the M transformation temperature increases, the R transformation temperature decreases, the M transformation temperature hysteresis decreases, and the alloy’s characteristics at room temperature change from SME+SE to SE. Ti-50.8Ni alloy spring shows SME+SE with deforming temperature Td＜20 oC, and it shows SE with Td＞30 oC. The stress-induced martensite stress of the alloy spring increases with increasing Td.