Recrystallization behavior and grain boundary character evolution in Co-Cr alloy from selective laser melting to heat treatment

Co-Cr alloy fabricated by selective laser melting was used to investigate the recrystallization behavior and grain boundary character evolution from As-SLM to isothermal annealed at 1200 °C for 5 min to 60 min. The As-SLM Co-Cr alloy has a prominent residual strain, high densities of dislocations and stacking faults, and solute segregation along the subgrain boundaries. The driving force for recrystallization of As-SLM Co-Cr alloy is mainly provided by phase transformation rather than crystal defects, which also offer plenty of routeways for both low- and high-angle grain boundary diffusion. In addition, the stacking faults in As-SLM Co-Cr alloy can generate morphologically complex twins by extending and gliding. The obtained optimal Co-Cr alloy has a large fraction (more than 80%) of special boundaries (Σ3, Σ9, and Σ27) after complete recrystallization, which enables high designing freedom and near-net-shape production towards additive manufacturing (AM) compatible grain boundary engineering (GBE) processing strategy.