冷轧变形对Ni-43.5Ti-0.5V形状记忆合金超弹性和显微组织的影响

Effect of cold deformation on superelasticity and microstructure of Ni-43.5Ti-0.5V shape memory alloy

通过恢复率实验、拉伸实验和显微组织分析，研究冷轧变形对Ni-43.5Ti-0.5V形状记忆合金超弹性和显微组织的影响。结果表明：冷轧变形对NiTiV形状记忆合金超弹性具有显著影响。随变形量的增加，合金超弹性呈现先增加后减小的变化规律。当变形量大于15.4%后，大量位错产生，马氏体变体和形变孪晶组织增多且分布致密，起到强化母相、抑制滑移变形的作用，使合金超弹性显著提高。当变形量大于29.1%时，剧烈的组织畸变导致出现过饱和的高密度位错，促使组织非晶化，超弹性开始减小。当变形量在23%~25%范围内变化时，合金获得最佳的非线性超弹性。单独依靠冷轧变形不能使NiTiV合金呈现完全非线性超弹性。另外，恢复率实验能够改善合金的超弹性，并发现了超弹性的稳定性变化规律。

The effects of cold deformation on the superelasticity and microstructure of Ni-43.5Ti-0.5V shape memory alloys （SMA） were investigated by recovery rate test, tensile test and microstructure observation. The results indicate that cold deformation has an evidence influence on the superelasticity of NiTiV SMA. With the increase of the deformation, the superelasticity of the alloy increases first and then decreases. When the deformation is more than 15.4%, a large number of dislocation appears, and the microstructures of martensite variants and deformation twins increase with their compacted distribution, which can strengthen the parent phase, inhibit slip deformation and make the superelasticity of the alloy improved significantly. When the deformation is more than 29.1%, the serious distortion of microstructure makes the supersaturated high density dislocation generated, which promotes the microstructure to turn to the amorphous. The superelasticity of the alloy begins to decrease. When deformation is in the range of 23%-25%, the best non-linear superelasticity of the alloy can be obtained. In a word, non-linear superelasticity of the alloy cannot be obtained only under the condition of cold deformation. In addition, the recovery rate test can improve the superelasticity of the alloy and the variation of the stability of superelasticity was found.