Influence of heat treatment and mechanical cycling on hardness and fracture analysis of Ti35Nb5Zr casting alloy

Resumo

Titanium alloys are used in Dentistry due to their excellent mechanical, physical and chemical properties. However, it is necessary to find a biocompatible alloy to substitute the Ti-6Al-4V alloy. The presented suggestion was to study mechanical properties of a new titanium alloy without toxic elements. The Ti-35Nb-5Zr (%wt) alloy was produced by arc melting method. The tests were Vickers hardness, tensile strength and mechanical cycling, according to technical standards for titanium biomaterials. Hardness tests were performed in three different stages: before and after heat treatment at 1000°C for 1h, and after mechanical cycling test. The fracture analysis was evaluated by scanning electron microscopy. The mean values of Vickers hardness were 230.3±27.06HV before and 462.6±59.44HV after heat treatment (P<0.0001). The mean hardness values were different among the samples after mechanical cycling test. The comparison of hardness mean values after heat treatment and after dynamic test shows a decrease of the results. The maximum tensile strength mean value, obtained from tensile test, was 3,440N. It was observed, microscopically, the presence of dimples after mechanical cycling test. It was concluded that the hardness values were different at each step and the predominant fracture was the ductile type.

Keywords: Alloys; Hardness tests; Tensile strength; Titanium.