Effect of duplex aging on microstructural and mechanical behavior of a new β-Ti alloy for biomedical applications

The influence of duplex aging on the microstructural and mechanical behavior of Ti-25Nb-10Ta-1Zr-0.2Fe alloy was investigated. The first step of duplex aging (DA) treatments was carried out at 300 degrees C or 400 degrees C for 20min and 1 h, followed by the second step aged at 550 degrees C for 20min-24 h. A small amount of athermal omega (omega(ath)) formed in the b matrix after solution treatment and water quenching. During single aging (SA) at 550 degrees C, upon slowly heating process, the omega(ath)/isothermal omega (omega(iso))-> isothermal alpha '' (alpha(iso)'') might occur. Subsequently, the alpha(iso)'' dissolved rapidly and transformed into alpha phase at the early stage of aging, resulting in a fine distribution of alpha precipitates in the beta matrix. During DA treatments, the fine omega(iso) and alpha(iso) were observed in the first stage aging at 300 degrees C/400 degrees C, then the metastable omega(iso) and alpha(iso)'' decomposed into alpha phase at higher temperature of 550 degrees C. Besides fine a laths, ladder-shaped alpha clusters with large size were observed after DA. There was a single-peak in the hardness curve of SA, and the peak hardness was associated with the uniform distribution of fine plate-like alpha phase. After DA treatments, the alloy showed stronger age-hardening and displayed obvious double-peak precipitation hardening. The first hardness peak was the result of the dense omega(iso) nano-particles formed in the first aging stage, while the second one could be mainly attributed to these large ladder-shaped alpha clusters in the second aging stage. Compared with SA, the balance between high strength and low modulus could be improved by an appropriate DA treatment. (C)2022 The Authors. Published by Elsevier B.V.

Automated summary

The influence of duplex aging on the microstructural and mechanical behavior of Ti-25Nb-10Ta-1Zr-0.2Fe alloy was investigated. The results showed that duplex aging treatment can improve the strength and hardness of the alloy, resulting in a fine distribution of α precipitates and the formation of large ladder-shaped α clusters.