Characterization of Ni–Mn–Ga alloy with Gd addition

The effect of rare earth element Gd additions in an Ni–Mn–Ga alloy on magnetocaloric effect has previously been investigated. In this paper, the microstructure of Ni53.4Mn20Ga25.6Gd1 was studied by TEM. The results show that Gd partly dissolves in the matrix and partly occurs as precipitates such as Gd and Ni-rich Ni–Mn–Ga–Gd quaternary phases. At room temperature, the alloy is mainly composed of non-modulated martensite with a small amount of seven-layered and ten-layered modulated martensite. The high-resolution electron microscopy (HREM) images also reveal that some layered structures in certain zones are microtwins in nature with a thickness of a few atomic planes as the stacking sequence is not periodic.