Effect of Ti addition on the mechanical properties and the magnetocaloric effect of Ni-Mn-In metamagnetic shape memory alloys

The effect of small amounts of Ti on the microstructure, mechanical properties and the magnetocaloric effect of a Ni-Mn-In metamagnetic shape memory alloy has been investigated. A strong grain refinement is observed as a consequence of the Ti addition, which in turn does not affect the crystallographic structure. Linked to the grain size reduction, mechanical properties such as microhardness and yield strength considerably increase with the increasing Ti content, following a Hall-Petch relation. Likewise, the MT temperature diminishes with the decreasing grain size, in spite of the increasing e/a. On the other hand, both the Curie temperature and the saturation magnetization of the martensite decrease as a result of the Ti addition. The lowering of the MT temperature brought by the grain refinement and the decrease of the saturation magnetization of the martensite that occurs as a consequence of the Ti addition result in a considerable enhancement of the magnetocaloric effect.