Laser powder bed fusion fabricated Cu-1.8Cr-1.0Nb-2.0Fe alloy with in-situ precipitation strengthening

Copper alloys fabricated by laser powder bed fusion (LPBF) have been widely utilized in a diverse range of industrial sectors, including electrical, electronics, aerospace, etc. This study centers on an LPBF-fabricated in-situ precipitation-hardening Cu-1.8Cr-1.0Nb-2.0Fe copper alloy and comprehensively investigates its densification, microstructure, mechanical properties, strengthening mechanisms, and coarsening resistance. The results demonstrate that optimal process parameters enable the fabrication of nearly full specimens with a relative density (RD) of 99.98%. The microstructure of the as-built (AB) and direct aging (DA) treatment specimens consists of columnar grains. During the LPBF process, an Nb(FeCr) core-shell nanostructure in-situ precipitates, inducing a strong precipitation effect that results in an exceptional ultimate tensile strength (UTS) of 444 MPa. After aging treatment, the average radius and volume fraction of the Nb(FeCr) core-shell nanostructure remains unchanged. Another reinforced phase of FeCr σ-phase forms to further enhance the tensile strength, resulting in a higher UTS of 498 MPa for DA specimens. Precipitation strengthening is the dominant mechanism among the four strengthening mechanisms for both AB and DA specimens. The excellent coarsening resistance of Nb(FeCr) core-shell nanostructure is confirmed by (i) the almost unchanged size and volume fraction after aging treatment and (ii) the close contribution value of precipitation strengthening induced by Nb(FeCr) core-shell nanostructure to YS for AB and DA specimens. This study provides valuable insights into the in-situ precipitation behavior for LPBF-fabricated copper alloys.