A CPFEM based study to understand the void growth in high strength dual-phase titanium alloy (Ti-10V-2Fe-3Al)

Abstract

High strength titanium alloys are generally used in widespread applications ranging over, but not limited to biomedical, aerospace, automotive, marine, oil and gas, and energy. Besides other manufacturing processes, forming is one of the common manufacturing process used to produce components out of these alloys. Forming processes generally involve significant plastic deformation of material under complex multiaxial loading conditions. Titanium alloys undergo considerable plastic deformation before failure while later is governed by the mechanisms of void nucleation, growth and coalescence. A number of titanium alloys used for high strength applications are multiphase alloys having α and β phases. It has been reported in the past that the voids tend to nucleate on the phase boundaries. This study is focused on understanding the growth of the nucleated voids at two selected locations in a dual phase titanium alloy (Ti-10V-2Fe-3Al); globular α phase (hexagonal closed pack, HCP) and at the interface of lamellar α and β phases (α - HCP and β - body centred cubic, BCC). This is one of the very few 3D representative volume element (RVE) study of void growth in single crystal titanium (HCP), carried out using crystal plasticity finite element modelling (CPFEM) at higher triaxialities (ranging 1/3-3) and the first one on the interface of bicrystals with different crystal symmetry. The effects of initial porosity, crystal orientation and the Lode parameter on void growth in single crystal (α-HCP) has been studied and it is found that they affects void growth considerably. An effort has been made to explain the physics behind it. In the second part, growth in a void at the interface of two distinct single crystals (α - HCP and β -BCC) was studied. The effects of Burgers orientation relationship (BOR) variant of the two phases, initial porosity, and phase boundary inclination (PBI) on void growth is investigated. It is found that the PBI has a very strong impact on the void growth. The effect of initial porosity is similar to the void growth in single crystals. Choice of BOR variant affected the void growth in moderate triaxialities.