Effect of ultrasonic vibration on microstructure and mechanical properties of Al0.4CoCrFe2Ni2 high entropy alloys reinforced by TiC with different scale

Strength of casting high entropy alloys (HEAs) improved by the introduction of ceramic particle. However, the strengthening process of alloys were hindered by the problem of particle agglomeration seriously. In this paper, the ultrasonic vibration (UV) treatment process was introduced to improve the dispersion of ceramic particles. Al_0.4CoCrFe₂Ni₂ HEAs contain different particle sizes TiC were successfully prepared. Morphology of TiC (μm) change from long straight rod to network structure with UV treatment, and the average dendrite spacing decreases. TiC (nm) particles were dispersed uniformly and agglomeration decreased remarkably. The mean free path ($\bar{L}$) of dislocation motion is increased greatly. Additionally, a new substructure region formed by introducing ceramic phase TiC. Dislocation density increased around substructure region after UV, the energy and driving force provided by UV for the overturning of substructure region to sub-grains. Ultimate tensile strength of UV-Al_0.4-TiC (nm) alloy reaches 572 MPa under the action of the second phase, Hall-Petch strengthening and other mechanisms, and the fracture elongation as high as 49.6 %. Compared with the non-ultrasonic alloy, the yield strength is increased by 10 %, and elongation after fracture is increased by 41.3 %. Compared with Al_0.4 matrix alloy, the yield strength is increased by 92.8 %. Therefore, the influence of UV assisted treatment on particle reinforced alloys with different sizes was analyzed in this paper. UV assisted treatment proved to provide an effective method to solve the agglomeration of reinforced particles and offer a novel pathway to design cast HEAs with an exceptional amalgamation of strength and ductility.