Achieving excellent strength-ductility combination through the control of intricate substructures in an additively manufactured Co–Cr–Mo alloy

Abstract

In this study, we successfully endowed a classical Co25Cr5Mo5W alloy with excellent strength-ductility combination by regulating the substructures during laser powder bed fusion (LPBF) and subsequent heat treatment. State-of-the-art characterizations reveal that the as-built Co25Cr5Mo5W alloy features integrated networks of dense cell boundaries and stacking faults within a near-pure face-centered cubic matrix, which jointly confer a high yield strength of ∼820 MPa and a high ductility of ∼22.3%. Upon heat treatment, the heavy decoration of solutes Cr, Mo, W, and Si at cell boundaries triggers heterogeneous nucleation and growth of Laves precipitates within 15 min. After that, global intercellular precipitation occurs, further boosting the yield strength to ∼1170 MPa at a decent ductility of ∼7.5% when heat-treated for 60 min. Such a finding establishes a clear connection between the substructures and the mechanical properties, offering valuable implications for surpassing the current mechanical limitation in the Co–Cr–Mo alloy family.