Microstructure and properties of equiatomic Ti-Ni alloy fabricated by selective laser melting
Microstructure and properties of equiatomic Ti-Ni alloy fabricated by selective laser melting
复制标题
选区激光熔化等原子Ti-Ni合金的组织与性能
DOI：
10.1016/j.msea.2019.138586
复制
发表时间：
2020-01-13
期刊：
影响因子：
6.4
通讯作者：
Zhang, L. C.
中科院分区：
文献类型：
--
作者：
Ren, D. C.;Zhang, H. B.;Zhang, L. C.
选择性激光熔化（SLM）作为增材制造技术之一，可用于制备形状复杂的Ti-Ni形状记忆合金。在这项工作中，等原子Ti 50 Ni 50（at.%）采用不同扫描速度的SLM制备了不同尺寸的样品，在低输入激光能量密度（40 J/mm（3））和1000 mm/s的扫描速度下获得了近全致密（相对密度99.5%）的零件。不同扫描速度对合金的相组成、相变温度和维氏硬度影响不大。在低倍镜下，SLM制备的Ti-Ni合金试样呈现典型的熔池形貌，显微组织不均匀，在高倍镜下观察到自适应马氏体（B19 '）孪晶和少量奥氏体（B2）、纳米Ti 2Ni和菱形（R）相。与Ti-Ni粉末相比，SLM制备的Ti-Ni合金具有较低的相变温度和较大的相变起始点和相变结束点之间的滞后温度，这是由于纳米Ti 2Ni相的形成和组织的不均匀性。SLM等原子Ti-Ni合金中R相的形成是由于特殊的重复加热过程和Ti 2Ni相与位错形成的应力场所致。SLM生产的Ti-Ni合金具有较高的压缩和拉伸断裂强度，但较低的压缩和拉伸断裂应变相比，传统的铸造样品。
Selective Laser Melting (SLM) as one of the additive manufacturing technologies can be used to produce Ti-Ni shape memory alloys with complex shape. In this work, equiatomic Ti50Ni50 (at.%) samples were produced by SLM with different scanning speed, and near-fully dense (99.5% relative density) parts were obtained under a low input laser energy density (40 J/mm(3)) with the scanning speed of 1000 mm/s. The different scanning speeds had limited influence on the phase composition, transformation temperatures and Vickers hardness. Under low magnification, the typical molten pool morphology with inhomogenous microstructure was shown in the samples of SLM-produced Ti-Ni alloy, and self-accommodate martensite (B19') twins with a few austenite (B2), nanoscale Ti2Ni and rhombohedral (R) phases were found at higher magnification. Due to the formation of nanoscale Ti2Ni phase and inhomogenous microstructure, the SLM-produced Ti-Ni alloy exhbited lower phase transformation temperatures and larger hysteresis temperatures between the start and finish point of the phase transformation compared to the Ti-Ni powder. The formation of the R phase was contributed to the special repeat heating process and stress field formed by Ti2Ni phase and dislocations In SLM equiatomic Ti-Ni alloy. The SLM-produced Ti-Ni alloy exhibits higher compressive and tensile fracture strength but lower compressive and tensile fracture strain compared to the conventional cast samples.