X-ray diffraction analysis and microstructures of laser powder bed fusion Ti6Al4V for application in aerospace structural components

Abstract

X-ray diffraction (XRD) is a powerful tool for analysing crystallographic structure and phase composition of materials. A metastable martensitic α’-phase is formed because of the laser powder bed fusion’s (LPBF) rapid cooling rates, whilst a balanced mixture of α and β phases for this material can be obtained upon post process heat treatment. XRD analysis provides insights into the volume fraction of α’-phase transformations upon post-processing at different temperatures. This paper explores the XRD-based phase identification of LPBF processed Ti6Al4V, emphasizing the effects of heat treatments on microstructural evolution. The as-built microstructure primarily consisted of fine acicular α’ martensite. Post-processing heat treatments, such as stress-relieving and annealing facilitated the transformation of α’ into a stable α + β microstructure. Following annealing, the acicular α′ martensitic microstructure of LPBF Ti-6Al-4V decomposes into a stable lamellar α+β microstructure. The resulting lamellar morphology consisted of alternating α and β laths within prior β grains.