Stabilized sub-grain and nano carbides-driven 1.2 GPa grade ultra-strong CrMnFeCoNi high-entropy alloy additively manufactured by laser powder bed fusion

Abstract

• Carbon-containing CrMnFeCoNi high-entropy alloys with varying carbon content were manufactured by laser powder bed fusion (L-PBF). • Aging treatment effects on the microstructural evolution and mechanical properties were investigated. • The alloy aged at 650 °C showed ultimate tensile strength of 1.2 GPa at room temperature. • The main deformation mechanism changed from deformation twinning to dislocation-mediated slip. High-entropy alloys (HEAs) with interstitial atoms that are produced by additive manufacturing have gained intensive interest in the materials science community because of their suitability for constructing high-strength net-shape components. Here, a strategy to additionally enhance the strength of selective laser melted carbon-containing HEAs was investigated. The as-built carbon-containing HEAs (C x (Cr 20 Mn 20 Fe 20 Co 20 Ni 20 ) 100- x ( x = 0.5 at.%, 1.0 at.%, and 1.5 at.%)) contain supersaturated carbon, and the extent of supersaturation increases as the carbon content increases. When subjected to aging treatment at 650 °C for 1 h, the microstructure of the three alloys did not change at the grain scale. However, the microstructure at the sub-grain scale changed markedly, and these changes influenced the tensile properties and deformation mechanism. In particular, the tensile strength of aged 1.5C-HEA at 650 °C was ∼1.2 GPa at room temperature, which is higher than those reported for CrMnFeCoNi HEAs. Furthermore, the main deformation mechanism changed from deformation twinning to dislocation-mediated slip, resulting in much higher strain hardening capacity after the aging treatment. This work led to the development of an alternative promising method that involves tailoring the microstructure, to enhance the mechanical properties of additively manufactured metallic materials that contain interstitial atoms.