Electrospark powders of shape memory alloys

Powders of Ti-Ni and Ni-Mn-Ga alloys are obtained by the electrospark method. It is established that the largest particles are of irregular shape and the smaller ones are spherical. Some spherical particles are hollow. No carbon contamination is found within the Ti-Ni and Ni-Mn-Ga powders obtained in cryogen liquids. The Ti-Ni powders of all compositions are mixtures of austenite and martensite phases. Preliminary heat treatment of spherical-particle Ni-Mn-Ga alloys is needed to activate their martensitic transformation. The martensitic transformation proceeds over quite a wide temperature range, which is indicative of high dispersion, and the martensitic temperatures increase, which is indicative of a minor difference between the chemical compositions of powders and massive samples.[PUBLICATION ABSTRACT]