Microstructural and Mechanical Investigation of NiTi Intermetallics Produced by Hot Deformation Technique

Abstract

This work has been carried out to bring an innovative approach to the difficulties encountered in the production of NiTi shape memory alloys by powder metallurgy (PM). For this purpose, new binder system, which was water soluble, was used for production of NiTi green parts. The green parts were sintered at \(1200\,{^{\circ }}\hbox {C}\) for 60 min, and then red parts were deformed at \(1000\,{^{\circ }}\hbox {C}\) for 40 and 50% deformation ratios. To observe the characterization of the microstructure and hot deformation effects, X-ray diffraction, scanning electron microscopy, mapping, microhardness and density measurements were applied to the samples. Experimental results show that the rhombohedral phase (space group R3), which was a lenticular disk-like morphology (disks), was detected at \(1200\,{^{\circ }}\hbox {C}\) sintered PM parts. 551HV microhardness and \(5.85\,\hbox {g/cm}^{3}\) density values could be achieved with the 50% hot deformation ratio. Furthermore, intermetallic components such as \(\hbox {Ni}_{4}\hbox {Ti}_{3}\), \(\hbox {Ni}_{3}\hbox {Ti}\), NiTi and NiTi \((\hbox {B}_{19})\), which directly affect the shape memory, are beginning to form in the microstructure with deformation.