Shape memory NiTi powders produced by electrode induction melting gas atomization (EIGA) method for additive manufacturing

Abstract

With the development of additive manufacturing technology, it provides an efficient method for preparing complex structured NiTi alloy specimens. Different additive manufacturing technologies have different requirements for powder particle size. In order to satisfy the requirements of additive manufacturing technology for powders. This study aimed to produce spherical NiTi powders suitable for additive manufacturing by electrode induction melting gas atomization (EIGA). Scanning electron microscopy, X-ray diffractometry and differential scanning calorimetry were used to investigate the surface and inner micro-morphology, phase constituent and martensitic transformation temperature of the surface and inner of the NiTi powders with different particle sizes. The results show that the powder mean particle size D50 was 75 μm, flowability was 19.3 s/50 g, apparent density was 3.40 g·cm^–3, and the oxygen content of the powder only 0.005% higher than the raw materials. That the grain of powder becomes finer gradually with decreasing particle size. Ingot and all the powders exhibit a main B2 phase. Particles with different particle sizes have experienced different cooling rates during atomization. Various cooling rates cause different grain size inside the powder; in particular, the transformation temperature decreases with decreasing particle size. This study provides a basis for preparing high quality AM NiTi parts.