Contributions of microstructural features to the integrated hardness of TA15 titanium alloy

Analysis of the contributions of microstructural features to integrated property of TA15 titanium alloy is a crucial issue for microstructure design and obtaining desired material properties. To this end, various microstructural features, such as equiaxed primary α phase (αp) and its boundary (αGB), transformed β matrix (βt) consisting of α plate and residual β phase (βbase) as well as the interface between them (βGB) were obtained by different isothermal compression and heat treatment conditions. Nanoindentation and Vickers hardness tests were then performed on these features to investigate their contributions to the integrated property. It is found that the hardness of αp varies slightly with the compression and heat treatment temperatures. The hardness of βt decreases while the hardness of integrated microstructure increases with increasing compression temperature. Moreover, the hardness values of βt and integrated microstructure are larger when the heat treatment temperatures are higher. By considering the hardness and volume fraction of each microstructural feature, it is also found that the contributions of microstructural features to the integrated hardness increase in the order of αGB, αp, βGB, βbase. The contributions of αp and αGB decrease while those of βbase and βGB increase with increasing compression temperature. In addition, the contributions of βbase and βGB to the integrated hardness can be further adjusted by heat treatment under different temperatures.