Influence of alloy element partitioning on strength of primary α phasein Ti-6Al-4V alloy

The partitioning effect of Al (alpha-phase stabilizer) and V elements (beta-phase stabilizer) on strength of the primary alpha phases in the alpha/beta Ti-6Al-4V alloy with the bimodal microstructure was investigated. It was found that partitioning of Al and V elements took place in the Ti-6Al-4V alloy during the recrystallization process, leading to the variation of the content of Al and V elements in the primary alpha phases with changing the volume fraction of the primary alpha phase. Nanoindentation tests reveal a general trend that the strength of the primary alpha phases increases with decreasing the volume fraction of the primary alpha phases, and such trend is independent on the loading direction relative to the c-axis of the alpha phase. The enhanced strength is attributed to the increase of the content of Al element in the primary alpha phase, but it is not dominated evidently by the change of the V content. The solid solution strengthening contributed from both the elastic strain introduced by the solute atoms and the variation of the density of states was estimated theoretically. (C) 2017 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.