Effect of Heat Treatment on Some Titanium Alloys Used as Biomaterials

Abstract

Titanium-based alloys are constantly improved to obtain properties suitable for their use. Improving titanium alloys is very important for performing alloys without side effects. In this paper effects of structure, microhardness, and indentation test of eight titanium alloys were investigated after aging. The heat treatment consisted of a high-temperature quenching accomplished in three steps (650 °C for 25 min, 850 °C for 20 min, and 950 °C for 20 min). The cooling process was accomplished using N2 gas, introduced in the chamber at a 9-bar pressure for 37 min. Then, followed by heating to a constant temperature tempering (550 °C) at 1.5 bar pressure and kept for 2 h and 10 min at 2 bar pressure. Optical microscopy images were obtained of Ti-Mo-Zr-Ta alloys with grain-specific aspects of titanium alloys; acicular and coarse structures are specific to β alloys. Microhardness results showed significantly influenced by the heat treatment, increased by approximately 5% for Ti15Mo7Zr15Ta1Si and Ti20Mo7Zr15Ta0.5Si, while for Ti15Mo7Zr15Ta0.5Si and Ti20Mo7Zr15Ta an approximately 9% decrease has been noted. The modulus of elasticity results obtained by the indentation method for the experimental alloys were between 36.25–66.24 GPa. The heat treatments applied to the alloys had a pronounced effect, improving both the structure of the alloys and the results of the indentation test.

Keywords

• biomaterials
• titanium-alloys
• heat-treatment
• microscopy
• microhardness