Synthesis of NiTi alloy from thin Ni/Ti multi-layer

DOI: 10.5176/2251-1857_M312.27

Authors: Jamaluddin Abdullah, Abdus Samad Mahmud, Yinong Liu

Abstract: This paper reports the synthesis of NiTi by solid state diffusion annealing of cold-rolled multi-layer Ni/Ti thin foil. Cold-rolled Ni/Ti thin foil of 50 μm annealed at temperature between 673 K and 1073 K exhibits multiple phase formation during annealing. At lower temperature annealing, Ni(Ti) NiTi2, NiTi, Ni3Ti and Ti(Ni) were formed. Phase formation mechanism conforms to the previously proposed model. At higher temperature annealing NiTi phase increased while Ni(Ti) and Ti(Ni) dissappeared. The heavily rolled thin foil underwent amorphization, crystallization and alloying process during annealing. The multilayer foil exhibits thermal transformation behavior similar to cold-worked NiTi alloys, with two-step transformation involving the R-phase transformation observed when heat treated at below 873 K. The annealed specimen exhibits shape memory effects and almost texture free microstructure. This provides alternative processing for texture free NiTi alloy from thin sheet.
Keywords: NiTi shape memory alloy; annealing; thin foil; phase formation; transformation