Balancing the mechanical properties of Al0.45CoCrFeNiTix high-entropy alloys by tailoring titanium content

In this study, the microstructure and mechanical properties of Al0.45CoCrFeNiTix (x = 0, 0.25, 0.5, 0.75, 1.0) high-entropy alloys were investigated. Various techniques including XRD, SEM, EBSD, and TEM were employed, along with hardness tests, compressive tests, and tensile tests conducted at room temperature. Our findings reveal that the alloy's microstructure changes from FCC + BCC to FCC + BCC + L21 phase as the Ti content increases. Specifically, the BCC content increases from 0.9 % to 62.3 %. This alteration in microstructure leads to a significant enhancement in the compressive yield strength of the alloy, from 305.96 MPa to 1492.53 MPa. The observed strengthening effect can be attributed to the increased BCC content and the formation of the L21 phase within the alloy. The results of the tensile experiments demonstrate that the Ti0.25 alloy exhibits the most favorable overall properties, possessing a yield strength of 619 MPa. This represents a significant increase of 64.6 % when compared to Ti0. The strengthening mechanism of the Al0.45CoCrFeNiTix high-entropy alloy is thoroughly discussed. The main strengthening mechanisms of the alloy system are fine grain strengthening, solid solution strengthening and second phase strengthening. This study achieves a balance between strength and ductility by modulating the phase composition of the alloy, laying the foundation for further development and research into the properties of the high-entropy alloys.