Achieving high strength and ductility in high-entropy alloy particle reinforced Al matrix composites with proper proportion of layered structures

Abstract

Particle spatial distribution has a significant influence on mechanical behavior of particulate reinforced Al matrix composites fabricated by powder metallurgy, which has been systematically investigated in our work. The results showed that, by regulating the milling time for 1 h, 10 h and ≥ 20 h, assisted by hot pressing and hot extrusion processes, three typical distributions of high-entropy alloy (HEA) particles within the Al matrix composites were constructed, i.e., particle agglomerated composite, uniformly distributed composite, and layered structure composite, respectively. After a long-time high energy milling, alloying behavior did not occur between the Al and HEA particles. Moreover, the composite with a proper proportion (19 vol%) of layered structures achieved good combination of yield strength (445.2 MPa) and fracture strain (5.4%), which was ascribed to the strengthening and toughening effect induced by bimodal gain structure. The effect of layered structure on the composite was reflected in two points: first, due to the differences in dislocation density and consumption degree of Cu atoms, the size and density of precipitates in the large particle zones differ from those in the layered structured zones. Second, according to the finite element analysis, though high content of layered structures brought high strength in the composites, it also caused stress concentration, which could reduce the ductility of composites. The dominant strengthening contribution of the layered structure in the composites was derived from the grain boundary strengthening. This research provides a new insight into Al matrix composites with different reinforcing particle distribution.