Achieving enhanced mechanical behavior in additively manufactured CoCrNi MEA via Al/Ti doping under medium strain rate and cryogenic conditions

Selective laser melting (SLM), an advanced powder-bed fusion technique employing a high-power laser beam for selective melting and consolidation of metallic powder layers, has exhibited remarkable capabilities in fabricating advanced alloys with controllable microstructures and mechanical properties. For SLM-fabricated medium-entropy alloys (MEAs), a comprehensive understanding of the strain rate- and temperature-dependent deformation mechanisms remains a critical challenge, especially under cryogenic conditions. In this study, the effects of strain rate and temperature on the microstructure evolution and mechanical behavior of SLM-fabricated (CoCrNi) 94 Al 3 Ti 3 MEAs were systematically investigated. The experimental results demonstrated that the as-prepared MEAs had a pronounced strain rate sensitivity, and optimal mechanical properties can be achieved at intermediate strain rates through an exceptional balance between strength and ductility. Under cryogenic loading conditions, the (CoCrNi) 94 Al 3 Ti 3 alloy exhibited enhanced mechanical properties with the strength of 1150 MPa and elongation of 50%, which can be ascribed to significant grain refinement, and extensive activation of deformation twinning. The synergistic strengthening effects, including L1 2 precipitate strengthening, solid solution hardening, grain boundary strengthening, and temperature-dependent twinning mechanisms play the dominant role in mechanical property enhancement. This work provides comprehensive insights into the fundamental deformation mechanisms in SLM-fabricated MEAs.