EVOLUTION OF MICROSTRUCTURE IN Ti15Mo ALLOY DEFORMED BY HIGH PRESSURE TORSION DURING LINEAR HEATING

摘要

The influence of severe plastic deformation on ongoing phase transformations in metastable β-Ti alloy Ti15Mo was investigated in-situ during linear heating by electrical resistance and complemented by ex-situ microstructure observations using transmission electron microscopy. Several non-monotonic regions in the temperature dependence of electrical resistance were identified and associated with corresponding phase transitions, namely the reversible diffusionless shuffle transformation of athermal to phase, followed first by diffusion controlled growth of isothermal to phase and subsequently its continuous dissolution. Formation of a phase at high temperature is associated with increase of the electrical resistance. The influence of severe plastic deformation on the phase transformations sequence is discussed in detail. For ex-situ microstructural observations different conditions were selected based on electrical resistance measurement. It was revealed, that lattice defects introduced by severe plastic deformation strongly influence the phase transitions during heating of the alloy.