Crystal plasticity finite element study of tensile behavior of two-phase titanium alloy Ti-6Al-4V

The influence of α/β volume fraction and grain size on the tensile mechanical properties of Ti-6Al-4V dual-phase titanium alloy was investigated in this study using the crystal plasticity finite element method. The contribution of different slip systems to plastic deformation was evaluated quantitatively by slip relative fraction. The results demonstrate that the stress-strain distribution during the tensile deformation of Ti-6Al-4V titanium alloy is non-uniform. The stress is primarily concentrated on the β phase grain and grain boundary, while the strain is concentrated on the α phase grain. Increasing the volume fraction of β phase leads to a larger stress concentration area, easier generation of strain concentration at the triple-junction of grain boundaries, and a significant increase in contribution from the β phase{110} slip system to the plasticity deformation. Increasing α, β or two-phase grain size results in decreased stress-strain curve in the plastic region, where initial deformation is predominantly governed by prismatic slip system while pyramidal <c+a> slip system contribute slightly less. An increase in α-phase grain size leads to a decrease in the activity of pyramidal <c+a> slip system, resulting in reduced stress values in the plastic region. Increasing the β-phase grain size results in a reduction of stress during the plastic stage, which is attributed to the decreased activity of {110} slip system within the β-phase. Simultaneously increasing the grain size of both the α and β phases will affect the activation fraction of prismatic and {110} slip systems. The reduction in stress is associated with the significant decrease in the number of interfaces.