Impact properties of half stress-relieved and hot isostatic pressed Ti–6Al–4V components fabricated by laser powder bed fusion

This study focuses on the impact properties of Ti–6Al–4V produced by LPBF using un-notched Charpy impact testing. The effects of the build orientation, impact orientation, and half stress-relief and hot isostatic press (HIP) heat treatments on the impact resistance were investigated. The impact properties of HIPed samples were significantly greater than those of stress-relieved ones. Microstructural analysis and fractography revealed that process defects such as porosity, and columnar grain boundaries play an important role in crack initiation and propagation in the stress-relieved samples. In the HIPed samples the orientation of prior-β grain boundaries with respect to the impact loading, and impact energy absorption by microstructural modification from the high strains promoting formation of globular α were the main contributors in the impact resistance of the samples. Consequently, the vertically-built HIPed samples demonstrated the greatest impact energy from the combination of the perpendicular prior-β grain boundaries to the impact and highest observed α globularization.