Effect of sintering temperature and late PCA addition on the microstructure and mechanical behavior of a heterogeneous-multiscale AlCoCuMnNi high-entropy alloy synthesized via mechanical alloying and spark plasma sintering

With high-entropy alloys (HEAs) surpassing traditional alloys in nearly every characterization aspect, the search for novel high-potential compositions has become increasingly important. AlCoCuMnNi is a newly designed HEA, developed based on literature review, theoretical calculations, and the mutual interactions of its constituent elements in similar HEAs. This alloy is processed using mechanical alloying and spark plasma sintering (SPS) to produce an ultra-fine-grained, heterogeneous microstructure. To optimize the processing route, samples with different powder stock conditions subjected to various sintering temperatures (900, 1000 and 1100 °C) and examined. The results demonstrated a significant influence of input parameters on the final microstructure and mechanical properties. Modifying powder morphology through late PCA addition or increasing sintering temperature led to a substantial rise in hardness (from 390 to 625 HV), while a moderate sintering temperature yielded an unprecedented balance between shear strength of 300 MPa and high hardness as 440 HV. The obtained mechanical properties were further justified using advanced characterization techniques, such as EBSD analysis. The microstructure of the processed alloys revealed a heterogeneous bimodal duplex FCC + BCC phase, contributing to varying mechanical responses within the same composition. This study not only introduces a new HEA with an optimal balance between hardness and shear strength but also highlights its adaptability. The alloy's ability to be tailored through different processing routes makes it a promising candidate for further optimization and potential applications in various industrial sectors.