Effects of tungsten addition on the microstructural stability and properties of Ti-6.5Al-2Sn-4Hf-2Nb-based high temperature titanium alloys

The microstructural evolution, oxidation resistance and mechanical properties of Ti-6.5Al-2Sn-4Hf-2Nb-based alloys with different contents of tungsten (W) additions ranging from 0 to 4.0 wt.% have been investigated in this study. The addition of W changed the microstructure from Widmanstatten colony of the W-free alloy to basketweave microstructure. After thermal exposure at 650 degrees C for 10 0 0 h, the retained beta phase became less continuous, and secondary beta nano-particles with high W concentration were pre-cipitated from alpha lamellas. Within alpha lamellas, the W was found to mainly partitioned into the secondary beta phase and refined the ordered alpha(2)-Ti3Al precipitates due to increased solubility of Nb in alpha(2) phase. High W addition increased activation energy for oxidation, promoting the formation of more uniform and compact compound oxides, therefore substantially enhanced the oxidation resistance of the alloy. Besides, the W addition also improved the room and high-temperature yield strength without obviously losing plasticity after long-time thermal exposure. The improved mechanical performance was mainly attributed to the introduction of more alpha/beta interfaces, the precipitation of secondary beta phase and the refined alpha(2) phase with Nb segregation. (C) 2021 Published by Elsevier Ltd on behalf of Chinese Society for Metals.

Automated summary

The microstructural evolution, oxidation resistance, and mechanical properties of Ti-6.5Al-2Sn-4Hf-2Nb-based alloys were improved by adding tungsten (W) at different contents. A higher W addition enhanced oxidation resistance and strength without significantly reducing plasticity of the alloy.