原位激光定向能量沉积NiTi形状记忆合金的微观结构和力学性能

The NiTi alloy is a key material in aerospace and biomedical fields owing to its excellent superelasticity and high shape memory effect. Laser directed energy deposition (LDED), as an advanced additive manufacturing technology, made the preparation of NiTi alloys with high shape memory effect possible. In this study, the NiTi alloy was fabricated via LDED using Ni and Ti powder feedstock. The microstructure, phase content, and phase transformation of the alloy were analyzed by XRD, phase fitting, SEM, EDS, and DSC. Next, the shape memory effect was tested using compressed cylindrical samples. When the laser energy density was low, several Ni4Ti3 phases were produced in the NiTi alloy. The Ni4Ti3 phase disappeared with an increase in the laser energy density. When the laser energy density was 20.0 J/mm(2), the NiTi alloy showed a high compressive breaking strength of 2878 MPa and a compression failure strain of 34.9%, and the sample also showed a shape recovery rate of 88.2% after 20 cyc of compression.