Microstructural Homogeneity and Mechanical Reliability in SLM-Fabricated MoNbZrTaW High-Entropy Alloys

Refractory high-entropy alloys (RHEAs) have attracted increasing attention for structural applications under extreme conditions; however, the uniformity and reliability of their mechanical properties remain critical challenges, particularly when processed by additive manufacturing. In this work, the microstructural heterogeneity and mechanical uniformity of a selective laser melting (SLM)-fabricated MoNbZrTaW RHEA were systematically investigated. Microstructural characterization revealed a dual-phase BCC structure with dendritic and interdendritic regions distributed along the build direction. Statistical analyses were employed to quantify variations in microstructure and mechanical properties, including hardness, fracture strength, yield strength, and fracture strain. The effects of strain rate and specimen aspect ratio on mechanical behavior were further examined through compression testing. Weibull statistical analysis demonstrated that strength-related properties exhibit high uniformity despite pronounced microstructural heterogeneity, whereas fracture strain shows comparatively greater scatter. The results indicate that solid-solution strengthening governs the mechanical response and helps mitigate the influence of microstructural non-uniformity. These findings provide important insights into the mechanical reliability of SLM-fabricated RHEAs under room-temperature quasi-static loading, and support their potential for further investigation in advanced structural applications.