Effect of rare earth Y addition on two-phase Ni53Mn22Co6Ga19 high-temperature shape memory alloy

Abstract

Abstract The microstructures, martensitic transformation, mechanical and shape memory properties of (Ni53Mn22Co6Ga19)100–xY x (x = 0, 0.1, 0.3) high-temperature shape memory alloys were investigated. It was found that small Y addition results in the refinement of grain size and the increase of γ phase volume fraction. These changes can effectively improve the tensile ductility and fracture strength of two-phase Ni53Mn22Co6-Ga19 alloy, up to the maximum values of 10.1 % and 592 MPa respectively at x = 0.1. However, it is proposed that Y(Ni, Mn)4Ga precipitate forms in the alloys with the addition of Y, and its amount increases with further increasing Y addition. The growth of the Y(Ni, Mn)4Ga precipitate results in a decrease in the tensile ductility at x = 0.3. Results further show that shape memory properties of the studied alloys are closely related to the refinement of grain size and the alloy yield strength. While adding 0.1 at.% of Y, the shape memory effect and recovery rate decrease, resulting from the refinement of grain size, compared to those of two-phase Ni53Mn22Co6Ga19 alloy. Subsequently they increase with further increasing Y content to 0.3 at.% due to the decrease in the alloy yield strength.