【摘要】 利用熔炼、锻造、轧制等手段成功制备出微米片TiNi/NbTi形状记忆合金原位复合材料,冷轧退火处理后的复合材料中TiNi片厚度达微米尺度。基于微米片TiNi与基体NbTi之间的简化并联模型,推导出微米片TiNi在约束态相变过程中的回复应力计算公式,公式中回复应力与复合材料中两相的体积比、基体弹性模量以及复合材料预变形前后的热膨胀应变有关。利用公式计算了微米片TiNi在基体NbTi约束下升降温过程中的回复应力变化。计算结果表明,在降温开始阶段,回复应力随着温度的降低而减小,未出现先减小后增大的变化,也未表现出明显的滞后,这与以往拉伸试验机测试的结果不同。随着温度进一步降低,母相TiNi在基体的作用下逐渐转变成具有不均匀变形度的继承变形马氏体使回复应力逐渐减小;在升温阶段,由于降温过程中形成的继承变形马氏体逐渐逆转变为母相而使回复应力随着温度的升高逐渐增大,最高可达630 MPa。更多还原

【Abstract】 An in situ lamellar TiNi /NbTi shape memory composite was obtained by melting,hot-forging and cold-rolling of an as-cast NbTiNi alloy. The thickness of TiNi lamella achieved micron level after cold-rolling and annealing. Based on the parallel model of TiNi and NbTi,a formula was deduced for calculating the recovery stress of micron-lamella TiNi during the constrained martensitic transformation. The recovery stress was related to the volume ratio of the two components,the elastic modulus of matrix and the thermal expansion strain of samples before and after pre-straining,and was calculated by the formula during constrained thermal cycling. The results showed that the calculated recovery stress decreased with temperature decreasing at the initial cooling,and did not show an obvious hysteresis or a wavy shape with first decreasing and then increasing. It was different from the test of tensile machine before. When the temperature further decreased,the recovery stress decreased gradually due to the transformation of TiNi from parent to inheriting deformation martensite with non-uniform deformation degree. During heating,the recovery stress increased gradually up to the maximum of 630MPa because of the transformation from inheriting deformation martensite to parent.更多还原