Influence of Processing Parameter on Phase Transformation and Superelastic Recovery Strain of Laser Solid Forming NiTi alloy
Influence of Processing Parameter on Phase Transformation and Superelastic Recovery Strain of Laser Solid Forming NiTi alloy
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DOI：
10.1016/j.jallcom.2022.164568
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发表时间：
2022-03
影响因子：
6.2
通讯作者：
Y. Feng;Bochao Liu;X. Wan;Qianwen Liu;Xin Lin;Pan Wang
中科院分区：
文献类型：
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作者：
Y. Feng;Bochao Liu;X. Wan;Qianwen Liu;Xin Lin;Pan Wang
具有超弹性和形状记忆效应的NiTi合金由于其优异的形变恢复能力、机械强度和生物相容性而被广泛应用。采用激光立体成形技术制备了Ni50.8Ti49.2合金预合金粉末。沉积工艺参数对沉积合金的组织、相变和形状回复均有影响。LSF沉积态Ni 50. 8 Ti 49. 2合金为沿沉积方向沿着外延生长的柱状晶，沉积层间有少量等轴晶。沉积态Ni50.8Ti49.2合金发生两步/多步马氏体相变。马氏体相变温度随沉积高度变化不大，而R相变温度基本不随沉积高度变化。在力学性能测试中，当激光功率为1700 W，扫描速度为680 mm/min时，试样的压缩超弹性回复率高达9.5%。此外，所有试样中均出现了Ti 2Ni析出相和R相，但只有该试样中的Ti 2Ni析出相和R相与基体具有一定的取向关系。通过压缩变形测试了其形状记忆特性，在激光功率为1500 W、扫描速度为480 mm/min的条件下，获得了形状记忆效应的最大恢复应变为6.1%.
NiTi alloys with superelasticity and shape memory effects are currently widely used because of its excellent deformation recovery ability, mechanical strength, and biocompatibility. The Ni50.8Ti49.2alloy was manufactured by using laser solid forming (LSF) technology with pre-alloyed powder in this work. The microstructure, phase transformation and shape recovery of the deposited alloy were influenced by the parameters used in depositing process. The as-deposited Ni50.8Ti49.2alloy formed by LSF is columnar crystals epitaxially grown along the deposition direction, with a small amount of equiaxed crystals appear between the deposition layers. Two-step/multi-step martensitic transformation occurs in the deposited Ni50.8Ti49.2alloy. The martensitic transformation temperature slightly changes with the deposition height, whereas the R transformation temperature basically does not change with the deposition height. In the test of the mechanical properties, sample with a laser power of 1700 W and a scanning rate of 680 mm/min has a compression superelastic recovery as high as 9.5%. Moreover, Ti2Ni precipitated phase and R phase appeared in all samples, but only the precipitated Ti2Ni and R phase in this sample had a certain orientation relationship with the matrix. Shape memory characteristics was also tested by compression deformation, and the maximum recovery strain of shape memory effect is 6.1%, which is obtained in the sample deposited with 1500 W laser power and 480 mm/min scanning rate.