Micro-mechanical deformation behavior of heat-treated laser powder bed fusion processed Ti-6Al-4V

Industrial implementation of heat-treated Laser Powder Bed Fusion (L-PBF) processed Ti-6Al-4 V components requires a thorough understanding of the plastic deformation mechanisms to predict the part performance in safety-critical environments. Here, we study the micro-mechanical deformation behavior of a heat-treated L-PBF processed Ti-6Al-4 V by in-situ uniaxial tensile loading, during which high-resolution strain fields were monitored by Scanning Electron Microscope (SEM) based Digital Image Correlation (DIC). SEM-DIC revealed: (i) the transformed beta phase accommodates higher strain than the primary alpha phase; (ii) strain accumulation in primary alpha occurs primarily at the interface regions where the Al content is lower; and (iii) needle-shaped secondary alpha precipitate in the transformed beta creates strain localization pathways that bridge the interfacial strain bands. Based on the in-situ deformation behavior, recommendations are made on microstructure tailoring and alloy design to prevent strain localization and enhance the quasi-static mechanical properties of L-PBF processed titanium alloy components.