In-situ alloying and microstructural control in high entropy alloys with nano-carbide-framework via powder bed fusion

Abstract

High-entropy alloys (HEAs) are renowned for their exceptional mechanical properties, making them ideal candidates for use in demanding engineering applications such as aerospace, automotive, and defense industries. However, optimizing the balance between strength and ductility in HEAs remains a formidable challenge. In this study, we introduce a novel approach to enhance the mechanical properties of FeNiCrCo-based HEAs through in-situ alloying with nano-carbide-framework. By integrating nano-carbon into HEAs during laser powder bed fusion (LPBF), we were able to induce the formation of carbon-enriched nanostructures during the rapid melting and solidification processes of LPBF. Our methodology focuses on the strategic modulation of unique submicron-scale dislocation networks and the development of a nano-carbide-frameworks within the HEA matrix. The presence of Cr_xC_y compounds primarily at the grain boundaries and within dislocation networks significantly contributes to the mechanical strength of the alloy. By varying the nano-carbon content, we achieved control over the alloy’s microstructures, enabling a tailored balance between ultimate strength and ductility. This in-situ HEA alloying approach leads to the formation of a highly coherent nano-carbide-framework with the matrix, which not only enhances the ultimate strength of the HEAs (achieving values close to 1.4 GPa) but also maintains improved ductility. The nano-carbide-frameworks enabled microstructural design of HEAs provides a potent method for enhancing both the thermal stability and mechanical performance of the alloys. Our study paves the way for future research on the applicability of HEAs for applications in extreme conditions, and offers novel insights and methodologies for developing next-generation HEA with optimized performance.