Preparation of nanostructured CoCrFeMnNi high entropy alloy by hot pressing sintering gas atomized powders

Pre-alloyed CoCrFeMnNi high-entropy alloy (HEA) powders were prepared by gas atomization and consequently hot pressing sintered (HPS) at 1100 degrees C for 2 h for fabrication bulk materials. Sintered equiatomic CoCrFeMnNi HEA exhibited a homogeneous FCC structured single-phase solid solution and equiaxed grains with an average size of similar to 16 mu m. Analyses using TEM showed that sheet-like metastable structures with a size of similar to 55 to 160 nm were formed in the sintered bulks. The nano-sized metastable structures were inherited from the gas atomized CoCrFeMnNi powders with nano-sized crystallites formed during the rapid solidification process. The room temperature yield and ultimate tensile strength of sintered HEA reached 358 and 778 MPa, respectively, and the alloy kept excellent plasticity of similar to 28 %. Investigations of the deformation substructures at specific strain levels with EBSD revealed the sintered CoCrFeMnNi HEA kept FCC structured single phase and the main deformation mechanism was dislocation slip. The strengthening mechanism can be attributed to the combination effects of grain refinement and the presence of nano-sized metastable structures.

Automated summary

The pre-alloyed CoCrFeMnNi high-entropy alloy demonstrated good uniformity and excellent mechanical properties after hot pressing sintering, maintaining high plasticity. The strengthening mechanism of the alloy is mainly attributed to the effects of grain refinement and the presence of nano-sized metastable structures.