optimization Possibilities of properties of niti alloys used as traumatology implants

Abstract

Shape memory alloy represents metallic material that can return to its original forms, shapes, or sizes when subjected to a process of memorization between two transformation phases. The basic application of these materials is always simple, i.e. where the material can be easily deformed by an external force and will recover its original forms when heated at a certain temperature. NiTi alloy is mainly characterized by its special properties, namely the shape memory effect and superelastic behavior, as well as the excellent corrosion resistance, high strength, low modulus of elasticity and biocompatibility. Due to its superelasticity, NiTi resembles to some human rigid tissues, including bones and tendons that enables its using in implants or tools for many medical cases in orthopedics, neurology, cardiology, interventional radiology, endodontics, etc. In this work, the effect of thermal treatment on physical-metallurgical properties of NiTi alloy was studied. Flat samples of NiTi alloy with a composition of 50.6 at% Ni and 49.4 at% Ti were solution treated at 850 °C and subsequently aged at 450 °C. The microstructures in as-received, solution treated or solution treated and aged stages were examined by means of optical or scanning electron microscopies. The analysis of the heat treatment effect on the microstructure and transformation temperatures was completed by Vickers microhardness measurement and by differential scanning calorimetry.