Substitutional effects of Al and Mn on the microstructure and mechanical response of Cantor-derived high-entropy alloys for nuclear structural applications

• Published in: Materials science & engineering. A, Structural materials : properties, microstructure and processing Vol. 923; p. 147674
• Main Authors: Adegbite, Muyideen, Tiamiyu, Ahmed A.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.02.2025
• Subjects: Al0.3CoCrFeNi; Dynamic deformation; Dynamic strain aging; High-entropy alloys; Mn0.3CoCrFeNi; Nuclear applications; Phase stability; Twinning-induced plasticity; Al0.3CoCrFeNi; High-entropy alloys; Twinning-induced plasticity; Dynamic deformation; Phase stability; Mn0.3CoCrFeNi; Nuclear applications; Dynamic strain aging
• ISSN: 0921-5093
• DOI: 10.1016/j.msea.2024.147674

As global energy demands rise, nuclear energy offers a clean and sustainable solution, albeit with safety concerns. Designing next-generation nuclear reactors requires advanced materials with stringent properties, and Cantor-derived high-entropy alloys (HEAs) recently emerged as promising alternatives to conventional nuclear structural-alloys. Among these, Al0.3CoCrFeNi is widely studied but is metastable, posing challenges for nuclear applications where stable and low void swelling single-phase FCC-alloys are preferred. Guided by empirical parameters and CALPHAD, we design and develop a novel Cantor-derived FCC-stable Mn0.3CoCrFeNi HEA as a potential substitute for Al0.3CoCrFeNi. The microstructure and mechanical behaviors of Al0.3CoCrFeNi and Mn0.3CoCrFeNi under uniaxial quasi-static and dynamic strain-rates were evaluated in three processing conditions—as-cast (AC), homogenized and cold-rolled (CR), and homogenized, cold-rolled and annealed (CRA)—as a first experimental installment towards Mn0.3CoCrFeNi candidacy. AC-Mn0.3CoCrFeNi exhibits unique “casting twin boundaries” and suppressed cell-structure. While the hardness and yield strength of the AC and CRA samples for both alloys are comparable, those of CR-Mn0.3CoCrFeNi surpasses CR-Al0.3CoCrFeNi due to higher prior-deformation twins and dislocation density in the former. Unique Type A serration-dynamic strain aging (DSA) is observed in AC and CRA-samples of both HEAs under room temperature/low strain-rate conditions, and it delays instability onset. Meanwhile, DSA suppression in CR samples and those under high strain-rates are attributed to increased dislocation-dislocation and phonon drag-dislocation interactions, respectively. Additionally, Mn0.3CoCrFeNi demonstrates a superior strain-hardening rate under all conditions due to Mn0.3CoCrFeNi's lower stacking fault energy and critical twinning stress. These findings establish Mn0.3CoCrFeNi as a mechanically-superior candidate for nuclear structural applications.