In the present work, the temperature and strain-rate dependence of the superelastic response behavior of NiTi shape memory alloys prepared via electron beam freeform fabrication (EBF3) technique and post-heat-treated is systematically studied. It is demonstrated that the response hysteresis of the EBF3-fabricated NiTi alloys during superelastic cycling decreases with increasing strain-rate at the same test temperature. However, the superelastic response of material gradually alters to a nearly linear mode with the increase of test temperature under the same strain-rate. The corresponding stable superelasticity recovery ratio decreases from 62.6 % to 47.6 % when the test temperature improves from 100 °C to 150 °C. This is mainly due to the activation of dislocations in the {011}<001> slip system of B2 austenite, in which they become plugged and entangled during plastic deformation, deteriorating the material superelastic recovery ability. These findings provide a selection basis for the service conditions of the rapidly prepared NiTi alloys under EBF3-fabrication and post-heat-treatment technology routes.

中文翻译：

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EBF3 制造和后热处理的 NiTi 形状记忆合金中超弹性响应的温度和应变率依赖性


在目前的工作中，系统地研究了通过电子束自由成形（EBF3）技术制备并进行后热处理的NiTi形状记忆合金的超弹性响应行为的温度和应变率依赖性。结果表明，在相同的测试温度下，EBF3 制造的 NiTi 合金在超弹性循环过程中的响应滞后随着应变率的增加而减小。然而，在相同应变率下，随着试验温度的升高，材料的超弹性响应逐渐转变为近线性模式。当测试温度从100℃提高到150℃时，相应的稳定超弹性恢复率从62.6%下降到47.6%。这主要是由于B2奥氏体的{011}<001>滑移系中位错被激活，在塑性变形过程中位错被堵塞和缠结，使材料的超弹恢复能力恶化。这些研究结果为EBF3制造和后热处理技术路线下快速制备NiTi合金的使用条件提供了选择依据。