Effects of Ti and Gd for Ga substitution on microstructure, magnetic and mechanical properties of polycrystalline Ni-Mn-Ga magnetic shape memory alloy

•Ti fully dissolves in NiMnGa-based single phase structure.•Gd addition promotes dual-phase microstructure in the NiMnGa-based alloy.•Ti for Ga substitution leads to the decrease of the martensitic transition temperature.•Gd shifts the martensitic transition temperature to the room temperature regime.•Ti and Gd improved the mechanical properties of the NiMnGa-based alloy. The present study is focused on the influence of Ti and Gd doping at the Ga site on the microstructure, magnetic and mechanical properties of the polycrystalline Ni50Mn25Ga20-xZx (x = 0 or 5, Z = Gd, Ti) magnetic shape memory alloys. Microstructure investigations show that reference Ni50Mn25Ga25 and Ti-doped alloys, both in the as-cast and annealed state, are single phase materials, whereas Gd-doped sample reveals dendritic dual-phase structure with substantial distinction between Gd-rich and Gd-poor regions. Thermomagnetic measurements expose reversible martensitic transition in the Ni50Mn25Ga25 and Ni50Mn25Ga20Ti5 alloys, where Ti addition to NiMnGa composition leads to the decrease of phase transformation temperature from TM = 193 K for reference sample to TM = 172.5 K for Ti-doped material. Furthermore, the Ni50Mn25Ga20Gd5 alloy does not experience fully martensitic transition. Temperatures of magnetic transformation also varies with chemical composition and equals to 379 K, 318 K and 370 K for the annealed Ni50Mn25Ga25, Ni50Mn25Ga20Ti5 and Ni50Mn25Ga20Gd5 alloy, respectively. Mechanical properties investigation based on the nanoindentation measurements shows beneficial influence of doping elements on material hardness. In addition, planar distributions of hardness allow to deconvolute mechanical properties of each individual phase of the Ni50Mn25Ga20Gd5 alloy.