Hierarchical microstructures and deformation behavior of laser direct-metal-deposited Cu–Fe alloys

Abstract

Cu25Fe75 and Cu50Fe50 (nominal composition, at. %) alloys were fabricated using laser direct metal deposition (DMD) based additive manufacturing technique. These alloys exhibit hierarchical microstructures with bi-phasic Cu and Fe dendrites that contain nanoscale precipitates of varying sizes and structures. In the Cu25Fe75 alloy, Fe dendrites contained nanoscale, coherent, metastable BCC Cu and semi-coherent FCC Cu precipitates while the Cu matrix had nanoscale, coherent, metastable FCC Fe precipitates. In the Cu50Fe50 alloy, Fe dendrites only contained nanoscale semi-coherent FCC Cu precipitates while the Cu matrix had nanoscale coherent metastable FCC Fe precipitates. Both alloys exhibited enhanced flow strengths in the range of 750–980 MPa and significant plasticity, in compression. The Cu25Fe75 alloy had lower yield strength than Cu50Fe50 alloy but higher maximum compressive strength due to higher strain hardening resulting from slightly coarser dendrites with hierarchy of nanoscale precipitation. • Laser direct-metal-deposition based additive manufacturing is used to make Cu–Fe alloys. • Alloys show formation of hierarchical microstructure in Cu matrix and Fe dendrites. • Metastable BCC and FCC Cu precipitates are present in Fe dendrites. • Only coherent metastable FCC Fe precipitates are visible in Cu matrix. • Alloy with more Cu content shows grain refinement and higher yield strength.