Formation Processes of the Α + Α 2 Structure in Model Pseudo-α-Titanium Alloys

Abstract—The effect of the initial structures of titanium alloys containing 10 wt % aluminum and additionally alloyed with molybdenum, niobium, zirconium, and/or tin, which are formed by quenching from various phase regions, on the structure formation in the course of prolonged isothermal annealing at 650°С is studied. It is shown that, in alloys quenched from temperatures corresponding to the β region to form the α' martensite, the decomposition of the martensite and formation of the α-, α2-, and β-phases mixture within initial martensite plates occur. In this case, the formation of the α2 phase is realized via the nucleation and growth mechanism. In the alloys quenched from temperatures corresponding to the two-phase region, the spinodal decomposition occurs within the primary α-phase crystallites, and the α + α2 structure characterized by a great amount of antiphase boundaries forms.