Development of new β Ti and Zr-based alloys in the Ta-(75-x)Ti-xZr system

Abstract

The main objective of this study was to produce two new biomedical alloys, Ta-(75-x)Ti-xZr (x = 25, 50 wt%), and to carry out a detailed analysis of the crystal structures, phase composition, lattice parameters, hardness, and elastic modulus of the alloys under the influence of heat treatments. After melting (as-cast condition), the two alloys were subjected to two heat treatments carried out at a temperature of 1000 °C: one with slow cooling in the oven (SC) and the other rapidly cooled with ice water (RC). From the structural and microstructural characterizations (XRD, SEM, and Rietveld), it was observed that the Ta-(75-x)Ti-xZr produced are α+β type alloys. However, the Ta–25Ti–50Zr alloy contains a more significant amount of β phase due to the β stabilizing action of Zr combined with Ta as a typical β stabilizing element. Regarding the cooling after heat treatments, rapid cooling (RC) promoted the formation of the metastable α" phase, and heat treatment followed by slow cooling (SC) promoted the formation of the α+β phases. The alloys’ hardness, elastic modulus, and atomic packing factor (APF) were affected by changes in the α and α" phases fraction. The SC treatment increased APF, hardness, and elastic modulus, while the RC treatment decreased elastic modulus, optimizing it for biomedical applications.