Achieving high strength in laser powder bed fusion in-situ alloyed copper-chromium alloy via nanoprecipitation and heterogeneous strain fields

Copper-chromium (Cu-Cr) alloys are critical for advanced thermal/electrical components in aerospace and automotive systems where geometrically complex designs are increasingly demanded. Laser powder bed fusion (LPBF) provides a pathway to fabricate such intricate structures, yet pre-alloyed powders constrain compositional flexibility. This study employs LPBF in-situ alloying of blended elemental Cu and Cr powders (0.5–2.0 wt% Cr) to fabricate high-performance Cu-Cr alloys. After direct aging at 500 °C (DA-500), Cu-2Cr achieves an ultimate tensile strength of 694 MPa, representing a 21.4 % enhancement over its as-fabricated state (571 MPa) and surpassing nearly all reported dilute Cu-Cr alloys. Microstructural analysis reveals that rapid solidification formed nanoscale Cr-rich precipitates averaging 2.42 nm, including metastable FCC-Cr with full coherency and stable BCC-Cr with semi-coherent interfaces, coexisting with Cr₂O₃ particles averaging 77.87 nm. DA-500 treatment induces controlled coarsening of BCC-Cr precipitates to 6.01 nm, inducing heterogeneous strain fields. The resulting strengthening combines strain field effects from lattice distortion with persistent Orowan mechanisms, synergistically overcoming typical coarsening weakening effects. The work establishes a pathway leveraging LPBF in-situ alloying and tailored aging to achieve unprecedented strength in additively manufactured precipitation-strengthened Cu alloys.