Dependence of strength and ductility on secondary a phase in a novel metastable-β titanium alloy

As a novel metastable beta titanium alloy, Ti-6Mo-5V-3Al-2Fe, it is essential to establish the correlation among its microstructure, strength and ductility. In this paper, transmission electron microscope (TEM) and scanning electron microscope (SEM) were used to observe the secondary alpha phase (alpha(s)) of the aged alloy. The strength and ductility of the alloy were characterized by a room temperature tensile test. The dependence of strength and ductility on the alpha(s) of the alloy was investigated. Results indicate that the minimum width and spacing of alpha(s) within beta grains can be obtained after being aged at 470 degrees C for 4h. As the increase of aging temperature and time, the average width and average spacing of alpha(s) increase. A relational equation among precipitation strengthening and spacing length of alpha(s) is established to analyze the strengthening mechanism. It is demonstrated that the average spacing length of alpha(s) plays a predominant role in the strengthening of the alloy. The aged alloy exhibits poor ductility due to the formation of continuous grain boundaries a phase (GB alpha). After being aged at 620 degrees C for 4h, Widmanstaeurotten a phase nucleates along beta grain boundaries and grows toward beta matrix (WGB alpha). The combination of alpha(s) spacing widening and WGB alpha formation obviously improves the ductility of the alloy. (c) 2022 The Author(s). Published by Elsevier B.V.

Automated summary

This study investigates the correlation between microstructure, strength, and ductility in a novel metastable beta titanium alloy, Ti-6Mo-5V-3Al-2Fe. TEM and SEM were used to observe the secondary alpha phase (alpha(s)) of the aged alloy, and a room temperature tensile test characterized its strength and ductility. The results show that the minimum width and spacing of alpha(s) can be achieved after aging at 470 degrees C for 4h. The study establishes a relational equation between precipitation strengthening and alpha(s) spacing length and demonstrates that the average spacing length of alpha(s) plays a predominant role in the alloy's strengthening. The alloy's ductility is improved by the widening of alpha(s) spacing and the formation of Widmanstaeurotten a phase (WGB alpha) along beta grain boundaries after aging at 620 degrees C for 4h.