Effect of isothermal ageing on microstructure, martensitic transformation and mechanical properties of Ni_(53)Mn_(23.5)Ga_(18.5)Ti_5 ferromagnetic shape memory alloy

摘要

The effect of isothermal ageing on the microstructure, martensitic transformation and mechanical properties of Ni_(53)-Mn_(23.5)Ga_(18.5)Ti_5 alloy has been investigated. The results show that Ni_3Ti precipitates are observed in aged samples. The martensitic transformation temperature decreases remarkably with increased ageing time, while the martensitic structure of these alloys is five-layered martensite at room temperature. Additionally, Ti doping can significantly enhance the compressive strength and improve the ductility of Ni-Mn-Ga alloy with the appropriate ageing treatment.