Effect of nano-Al2O3 addition on microstructure and mechanical properties of Ti2AlNb-based composites prepared by powder metallurgy

Abstract

To meet the commercial application, the mechanical properties of Ti2AlNb-based alloys must be improved. However, the strengthening mechanism of the Ti2AlNb-based composites with Al2O3 particles needs further to investigate. Nano-Al2O3/Ti‐22Al‐25Nb composites are prepared by mechanical alloying (MA), high-energy ball milling (HEBM), and hot pressing (HP). The purpose of this study is to identify the effect of Al2O3 content on the microstructure and mechanical properties of the composites. The results show that the grain size decreases, and phase transformation occurs with an increase in the Al2O3 content. With the increase of Al2O3 content from 2 wt.% to 6 wt.%, the microstructure of Ti2AlNb-based composites transformed from the ultrafine acicular O phase to the uniform equiaxed O phase. The hardness and ultimate compressive strength of the Ti2AlNb-based composites first increase and then decrease. The hardness of the composite is up to 8.6 GPa when the Al2O3 content is 6 wt.%, almost twice that of Ti‐22Al‐25Nb alloy. The hardening effect is the result of a higher volume fraction of the O phase and grain refinement with addition of Al2O3 particles. The optimal combination of hardness, ultimate compressive strength, and strain-to-failure of the composite with 2 wt.% Al2O3 is 5.9 GPa, 2190 MPa, and 8.1%, respectively. The strengthening mechanisms of Al2O3 phase dispersion and ultrafine acicular O phase precipitation are proposed and confirmed. This research offers a new idea for the wider application of Ti2AlNb-based composites.