Diffusion Bonding Preparation of AZ31B/Cu Composite and Analysis of Interface Microstructure

AZ31B/Cu bimetallic composite was prepared by diffusion bonding process under the condition of 500 degrees C, pressure of 2.5 MPa, holding time of 40 min and vacuum of 1.0 x 10(-2) Pa. The microstructures and mechanical properties of the interface diffusion zone for the AZ31B /Cu bimetallic composite were analyzed, and the growing mechanism of interfacial reaction layers was discussed. The results show that the grain boundary penetration is obvious due to the Cu enrichment an the side of Mg alloy. The microstructure of interface zone of AZ31B/Cu composite from Mg alloy to copper includes the grain boundary penetration layer composed of alpha-Mg and Mg-17(Cu, Al)(12)which was precipitated along the grain boundary of alpha-Mg solid solution, eutectic of alpha-Mg and Mg2Cu, intermetallic compound Cu2Mg, eutectic of alpha-Mg and Mg2Cu, and Cu(Mg) solid solution, respectively. The micro-hardness for bonding diffusion interface increase step by step from the base metal to the center of interface zone, and the maximal micro-hardness is 3510 MPa. The eutectic phase beside Cu2Mg does not appear at the same time, the eutectic phase is early generated at the interface of the grain boundary penetration layer and the Cu2Mg layer, and element Mg in eutectic phase diffuses to copper through the Cu2Mg layer, then eutectic phase is generated at the interface of Cu2Mg and Cu(Mg). The average shear strength of AZ31B/Cu composite reaches 61 MPa. The fracture surface of AZ31B/Cu composite is located within its interface diffusion layer, the fracture morphology mainly consists of a tearing ridge and a cleavage plane with different sizes.