关键词: 形状记忆合金, 选区激光熔化, 显微组织, 力学性能, 超弹性

Abstract: The energy input per unit volume changes with the laser power and scanning rate. The change of the process parameters on the influence of microstructure and properties of the selective laser melting (SLM) is investigated for the as-deposited Ni50.8Ti49.2. Considering the influence of different energy inputs on the sample microstructure of the scanning direction (SD) and deposition direction (BD), samples are observed by optical microscopy, it was found that with the increase of energy input, the defects of the metallographic structure gradually decreased along the deposition direction. The microstructure evolved from short, thick columnar crystals to slender columnar crystals. Phase constitution at room temperature is investigated by XRD. Most of the samples are B2 parent phase at room temperature, and some samples contained a small amount of Ti3Ni4 phase. At the same time, the microhardness test of the sample shows that the introduction of Ti3Ni4 phase increases the microhardness value in addition to the laser power. The transformation temperatures of different samples are investigated by differential scanning calorimetry(DSC). The cylindrical samples were subjected to compression test using a universal testing machine. The results show that the fracture strain of the sample was up to 42%, and the fracture strain of the high energy input sample is slightly lower. The superelasticity at room temperature increases significantly with the increase of energy input. When the compression strain is 10%, the superelastic recovery rate is as high as 90.2%.

Key words: shape memory alloy(SMA), selective laser melting(SLM), microstructure, mechanical properties, superelasticity