Mechanical Engineering; Mechanics of Materials; General Materials Science; Titanium alloys; Metastable phases; High-energy X-ray diffraction; Phase transformation kinetics
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Abstract:
The effect of heating rate on the phase transformation kinetics of a Ti-10V-2Fe-3Al metastable β titanium alloy quenched from the β field is investigated by fast in situ high energy synchrotron X-ray diffraction and differential scanning calorimetry. The initial microstructure is formed by α″ martensite and fine ωath particles distributed in the retained β-phase matrix. The phase transformation sequence varies with the heating rate as revealed by analysis of the continuous evolution of crystallographic relationships between phases. At low temperatures an athermal reversion of α″martensite into β takes place. This reversion occurs to a larger extent with increasing heating rate. On the other hand, diffusion-driven precipitation and growth of the ω phase is observed for lower heating rates accompanying the reverse martensitic transformation. Furthermore, the results show that the stable α phase can form through three different paths: a) from the ω phase, b) from α″ martensite and c) from the β phase.
