Fabrication, microstructure, and mechanical properties of Al-based metal matrix-TiB2 -HEA hybrid composite

Abstract

In this work, a metal matrix composite is made up of a cast Al-Si-Mg alloy (LM25) matrix with two variants of particle reinforcements, first one with 3 wt% TiB2 and 2 wt% CoCrFeMnNi high entropy alloy (HEA) and the other as 2 wt% TiB2 and 3 wt% CoCrFeMnNi (HEA) were used. These two composites were successfully fabricated through the stir-casting process. The microstructures and morphology of the developed composites are studied using TEM and SEM. In the fabricated composites, TiB2 and HEA particles were discovered to be evenly dispersed in the matrix phase. The XRD analysis showed the existence of both the reinforcement phases TiB2 and HEA particles along with the matrix phase. The mechanical properties were enhanced with the addition of the reinforcement phase when compared with the base metal. It is also observed that the tensile strength is enhanced with increased HEA content demonstrating almost same ductility. The LM25–2 wt% TiB2 − 3 wt% HEA composite demonstrated higher tensile strength (∼255 MPa) than the LM25–3 wt% TiB2-2 wt% HEA composite (∼230 MPa) and LM25 base alloy (∼160 MPa) due to the presence of TiB2 and HEA particles and the high dislocation density and contrasted very well in terms of strength and ductility with conventional LM25 matrix composites supplemented with ceramic particles. The mode of fracture was observed that the cleavage planes on the fracture surface with increasing with HEA content changes from dimple morphology of base metal.