Study of mechanical behavior and deformation mechanism in an α–β Ti–4.4Ta–1.9Nb alloy

This paper presents the results of a study on evaluation of mechanical properties and identification of deformation behavior and mechanisms in a dual phase Ti–4.4Ta–1.9Nb alloy, developed for service in highly corrosive environments. The alloy possessed good strength and ductility and was not very significantly influenced by microstructural variations like martensite, tempered martensite and equiaxed α. The alloy with predominantly equiaxed α and a random distribution of fine nodular β phase was subjected to room temperature tensile deformation. Fractography analysis showed a ductile mode of failure. Coalescence of the heterogeneously nucleated micro-voids leading to final fracture by a ductile mode during tensile deformation presents direct evidence for decohesion of α/β interface. The total strain was found to be accommodated by the constituent α and β phases. TEM analysis of the deformed α phase showed that both slip and twin were operative. While slip was predominant, twinning along (0 1 1¯ 1¯) and (1 0 1¯ 2) planes were also observed.