Texture Evolution during Thermal Processing of Ti-6Al-4V: A Neutron Diffraction Study

This paper reports results of phase transformation experiments in the α/β alloy Ti-6Al-4V from α→β→α on heating be- low and near the β-transus using in situ neutron diffraction. The development and evolution of crystallographic texture during the α→β→α phase transformation was determined. Annealing at a sub-transus temperature 1562K (850°C) shows similar α-phase and β-phase pole figures from room temperature up to 1562K (850°C), with a slight increase in the intensity of the β-phase pole figures, showing that the β-phase texture strengthens during heating. During cooling, the β→α transformation occurs very quickly and the initial alpha-texture obtained at room temperature is significantly weakened by the heat-treatment. Strengthening of the β-phase texture is observed on heating the sample from [1163K to 1253K (890°C to 980°C), respectively] and a Burgers relationship ((0002) α/(110) β and {11-20} α/{111} β) is seen with the α-phase texture at room temperature; but no evidence of variant selection was observed during α→β transfor- mation. During the β→α phase transformation on cooling, the Burgers relationship holds. This indicates a texture memory effect due to the growth of the primary alpha phase present at high temperature.