Phase stability and structural properties of heat treated FeCoNiAlSi0.5 high-entropy alloy

The present study explored the effect of heat treatment on phase stability, microstructure, and mechanical properties of FeCoNiAlSi0.5 high-entropy alloy (HEA) processed by mechanical alloying (MA) and spark plasma sintering (SPS). The results revealed the formation of a single-phase body-centered cubic (BCC) structure after 30 h of milling and the subsequent sintering process. Further, heat treatment at higher temperatures stabilizes the BCC phase and promotes the formation of a more homogeneous microstructure. The experimental results revealed that the maximum Vickers hardness for the sintered HEA was approximately similar to 1036 HV, while the ultimate compressive strength of similar to 3374 MPa was obtained for the HEA heat treated at 1000 degrees C. The nanoindentation tests provided the peak nanohardness (similar to 11.94 +/- 0.63 GPa) and elastic modulus (258 +/- 10.13 GPa) for the sintered HEA. The creep resistance improved up to 900 degrees C and then slightly reduced for the HEA heat treated at 1000 degrees C due to microstructural coarsening. Therefore, this study demonstrated that the HEAs exhibited excellent stability in terms of phase, microstructure, and mechanical properties, making these alloys ideal candidates for high-temperature applications.