Enhancement of mechanical and functional properties of welded NiTi by controlling nickel vapourisation

Abstract

This work investigates the effect of nickel vapourisation on mechanical properties and superelasticity of a NiTi wire by selecting the highest and lowest power within a laser processing window. The dominant phase at room temperature changes from austenite to a mixture of austenite and martensite under low power and high power condition, respectively due to higher nickel loss in the high power sample. Furthermore, the high power sample has more deviation from base material texture (111)_B2 that causes deterioration in mechanical properties compared with the low power sample with has 81% of base material strength. Better superelasticity of the low power sample (0.38% residual strain) was explained by the existence of the martensite phase and coarser grain structure in the high power sample.