Research on the pore defects formation and mechanical properties of Ti6Al4V for selective laser melting

Abstract

This study investigates the preparation of Ti6Al4V specimens under various process conditions using selective laser melting. A high accuracy thermal-fluid coupling model is developed to investigate the physical mechanisms underlying pore defect formation during processing. Micro-morphology is characterized using optical microscopy and scanning electron microscopy. The results indicate that the microstructure primarily consists of pin martensite α′ at high cooling rates (10⁶–10⁷ K/s). Pore defects resulting from incomplete melting of particles are observed within the sample under low heat input conditions. In contrast, a transient bubble is extruded from the base of the keyhole in the molten pool under higher heat input, leading to the formation of a keyhole pore defect (>20 μm) upon captured by the solid-phase line. From the perspective of porosity-induced damage, the mechanical behavior of samples fabricated under various process conditions is further examined. The results demonstrate that defects reduce the component density. Furthermore, defects lead to stress concentration and a deterioration in mechanical properties. Porosity is a critical factor in part qualification. Porosity can be reduced, and mechanical properties improved, by adapting the process based on the pore defect formation mechanism.