Microstructure and Properties of Shape Memory NiTi Alloy

Abstract

Many years ago, the shape memory alloys properties of Nickel Titanium (NiTi) were first discovered in the early 1960s, as shape memory alloys had many applied applications, in which oxidization problems were not of concern for the most part. However, over the past decades, NiTi alloys have been increasingly considered in external and internal biomedical devices, for example cardiac stent wires, orthodontics, vascular and bone fractures, fixing plates and screws, self-expanding urinary tracts.. The aim of the research is to study the effect of the elements mobidium and zirconium on the shape memory alloys. When adding small amounts of zirconium leads to a smoothing of the granular size, when adding Mobidium improves the hardening process. The alloy was prepared from primary powders of nickel and titanium, using metallic powder technology, under pressure of 800 MPa. Then the sintering method was carried out in a 4-10 tor vacuum at 950 ° C. The results upon XRD analysis revealed that NiTi were completely changed into NiTi (both cubic and mono phases) and Ni3Ti phase. The samples are ground in a dry atmosphere and the samples are polished after sintering. Optical microscopy, x-ray diffraction techniques. hardness test was conducted using Vickers hardness machine. It was observed that as the Zr content is increased, the hardness values, in VPN, increased. For instance, equi at 30% of Ni Ti had a hardness of 127.05 which increased significantly as Zr content was increased to 20 at %. This is mainly observed due to precipitation hardening which occurs due to the presence of multiple phase in alloy D. Increase in hardness also suggests that the workability. It was observed that as the Mo content is increased, the hardness values, in VPN, increased. For instance, Ni Ti had a hardness of 127.05 which increased was increased to 40at%. This is mainly observed due to precipitation hardening which occurs due to the presence of multiple phase in alloy G. Due to molybdenum, Optical microscopy reveals surface characteristics such as open pores and grain borders, as well as the distinction between the phases NiTi and Ni3Ti.