CAUSE AND CATASTROPHE OF STRENGTHENING MECHANISMS IN 7020/AL2O3 COMPOSITES PREPARED BY STIR CASTING PROCESS AND VALIDATION THROUGH FEA

The present research has been focused to study causes and misfortunes of strengthening mechanisms in 7020/Al2O3 metal matrix composites. It was found that the tensile strength and stiffness increase with increasing volume fraction of Al2O3 particulates. The tensile strength and stiffness were decreased with increased size of particulates. After heat treatment, most of the coarse intermetallic phases are dissolved to form stable MgZn2, Al2Mg3Zn3, and Al2CuMg compounds. A clustering of particulates was observed in the composites having very small particles. The wettability and uniform distribution of particles have improved the strengthening mechanism. The proposed formulae by the author for the tensile strength and elastic modulus could predict them very close to the experimental values of 7020/Al2O3 composites. The FEA results validate the occurrence of particle debonding, porosity, and clustering in the composites.