The effects of Fe content on the microstructural evolution and tensile properties in Ti-6Al-4V-(2,4)Fe alloys fabricated by thermomechanical powder consolidation

Two Ti-6Al-4V-(2, 4)Fe (wt.%) alloys were fabricated by thermomechanical powder consolidation. With 2 wt% Fe, the microstructure consists of grain boundary alpha layers and interpenetrating networks of alpha plates filled by the alpha/beta lamellar structure. In contrast, with 4 wt%Fe, the microstructure consists of grain boundary alpha layers and alpha plates dispersed within a matrix of ultrafine beta transformed structure. Fe partition between beta and alpha and the beta stabilization effect of Fe restrict the growth of alpha and depress the beta ->alpha phase transformation to a lower temperature. Hence, the volume fraction of beta increases with the increasing Fe content. Due to solution hardening of Fe and alpha/beta interface strengthening, a 4 wt%Fe addition increases the yield strength to 1.342 GPa. However, the high flow stress sustained by 78 vol% ultrafine beta transformed structure may cause a significant strain localization in the weak grain boundary alpha layers, leading to intergranular fracture at a fairly small strain of only 1.6%. In contrast, with the addition of an appropriate amount of Fe which is likely around 2 wt%, a good combination of strength and tensile ductility can be achieved.

Automated summary

Two Ti-6Al-4V-(2, 4)Fe (wt.%) alloys were fabricated by thermomechanical powder consolidation. The microstructure and properties of the alloys are significantly influenced by the Fe content, with a good combination of strength and ductility achieved at around 2%Fe and potentially leading to intergranular fracture at 4%Fe due to strain localization.