Effects of milling and heat treatment on the synthesis of NiTi powders

Abstract

This work reports on the production of Ni-50 at% Ti powders by a planetary ball mill in various times (0.5, 1, 2, 6, 20, 36, 54 and 120 h) and subsequent heat treatment in Ar atmosphere at 820 °C. Study of powders structure after milling and heat treatment was carried out by scanning electron microscopy and X-ray diffractometry. According to the results, after milling for 6 hours NiTi phase formed, and by the milling evolution up to 54 h, it became the dominant phase. It was found that by the milling development, a layer structure in powder particles was formed, also by increasing the milling time a more homogeneous structure was obtained. Amorphous NiTi transformed into ordered NiTi, Ni3Ti, NiTi2 and minor TiO2 and TiO after heat treatment at 820 °C for 1 h.