Modify the interface between ex-situ -Al₂O₃ and Al matrix via in-situ coating in an Al matrix composite

In this study, an Al matrix composite reinforced with both ex-situ and in-situ gamma-Al2O3 particles was prepared through the liquid-solid reaction. Most of the in-situ gamma-Al2O3 particles distribute along grain boundaries, while the ex-situ gamma-Al2O3 particles were simultaneously coated by in-situ gamma-Al2O3 with a thickness of several nanometers. This coating structure is supposed beneficial for enhancing the bonding strength between ex-situ gamma-Al2O3 and the Al matrix. The ultimate tensile strength of the composite is tested to be 362 MPa at room temperature, while the strength can still be high to 205 MPa at 350 degrees C. This study sheds new insights to resolve the problem between ex-situ particles and the matrix in metal matrix composites.