The effect of β-phase condition on the tensile behaviour in a near-β Ti alloy produced by blended elemental powder metallurgy

Abstract

Abstract In this study, a Ti-10V-3Fe-3Al alloy produced by the blended elemental powder metallurgy technique was subjected to two heat treatments at 675 ℃ and 625 ℃ , resulting in lower β-phase stability and larger β-domain size in the sample heat treated at the higher temperature. The microstructural response to uniaxial tensile loading for the two conditions was investigated using a combination of optical microscopy, electron back-scattering diffraction and transmission electron microscopy. The observations indicate that a majority of deformation-induced products are formed in the vicinity of the fracture surface due to stress tri-axiality. Within this region, the 675 ℃ sample accommodated deformation via dominant { 332 } 〈 113 〉 twinning, α ″ martensite formation and limited { 112 } 〈 111 〉 twinning. On the other hand, the sample with higher β-phase stability accommodated deformation via α ″ martensite formation and perfect slip with reduced twinning activity. The formation of deformation-induced ω D phase between the β matrix and α ″ martensite laths was also observed in the sample with lower β-phase stability. Reduction of the interfacial energy by stress relaxation is assumed to be the driving force for ω D formation.