On the microstructural evolution and failure mechanism in laser powder bed fusioned Ti–6Al–4V during low cycle fatigue at room and elevated temperatures

Microstructural features and their evolution during cyclic deformation directly impact the low cycle fatigue (LCF) life of additively manufactured Laser Powder Bed Fusion (LPBF) Ti–6Al–4V. Tensile strain controlled LCF tests were performed at room (RT) elevated temperature (ET, @ 400 °C) to study softening behaviour failure mechanism LPBF The α′ grains free dislocation density studied using Electron Backscatter Diffraction (EBSD). Ti–6Al–4V has greater tensile strength than conventionally wrought due its microstructure, with fine needles which provide small slip lengths. For loading ET, interaction between dislocations increases in-turn ability material overcome obstacles motion, resulting in higher compared RT test. During deformation, substructures takes place subsequently produce Low Angle Boundaries (LABs) inside prior α’ grains. LABs progressively lead nucleation coalescence voids cycles, eventually leading fracture. An increase range (i.e. plasticity level) causes more significant pile-up, contributing a amount softening. lack fusion or pores, present near surface, microcracks, rough act as crack initiation locations propagate cause fracture under loading, where primary mode observed is intergranular.