Effects of Heat Treatments on the Structure and Mechanical Properties of Ti-25Nb-8Sn Alloy

Abstract

This study explores the effects of various heat treatments on the structure and mechanical properties of Ti-25Nb-8Sn alloy (wt.%). After a β solution treatment at 1100 °C for 10 min, the samples were subjected to water quenching, furnace cooling, or air cooling. Additionally, aging treatment was performed on the specimens in a vacuum furnace at 400, 500, and 600 °C for 45 min. The experimental results showed that the microstructure and mechanical properties of these alloys have changed under different heat treatment conditions. The as-cast Ti-25Nb-8Sn alloy was comprised entirely of the β phase, whereas the β+α phases were found in the furnace-cooled specimen. The air-cooled sample mainly consisted of the β phase and a small amount of the α″ phase. The water-quenched sample exhibited the β phase after it was cooled from 1100 °C. In addition, after aging at 400 °C, only the β phase was found. After aging at 500 or 600 °C, the β phase still existed, while a small amount of the α phase also appeared. Moreover, as the aging temperature increased, the intensity of the α peaks was increased. It is worth noting that the Ti-25Nb-8Sn alloy age-treated at 400 and 500 °C exhibited much higher bending strength/modulus ratios, some of which were as great as 23.14 and 24.86, respectively, than that of c.p. Ti (8.5) and Ti-6Al-4V (17.4). Thus, from the perspective of low modulus and high strength/modulus ratio, the Ti-25Nb-8Sn alloys age-treated at 400 and 500 °C are both suitable candidates for biomedical applications.