Experimental Study Of Phase Interface Of Al/Cu/Mg Ternary Diffusion Couple

Vacuum diffusion welding of heterogeneous metals has important applications in industry and the interface diffusion layer plays an important role in the welding joint. Al/Cu/Mg diffusion couples made by inlaying method are heat-treated in vacuum annealing furnace, then the diffusion-reaction zones of Al/Cu/Mg diffusion couples'binary and ternary phase interface were researched to identify their character by the means of optical microscope, scanning electron microscope and electron microprobe analysis. Furthermore, the mechanism of the interface diffusion layers formation and the factors of their formation and development have been analyzed. It has been shown that temperature is the most important factor in the diffusion process . The types of the interface diffusion layers are different with the shifts of temperature. The Al/Cu diffusion layer is consist of CuAl,CuAl₂,Cu₄Al₃ at 350-550℃,while CuAl,CuAl₂,Cu₄Al₃,Cu₅Al₃ at 600℃; Al₆CuMg₄,Al₇Cu₃,Mg₆Al₂Cu,MgAl₅,Cu₆Mg₂ and Cu₅Al₃ are obtained at 450℃in the zone marched with Al,Cu and Mg, while Al₂CuMg,Al₇Cu₃Mg₆,Cu₉Al₄ are obtained at 500℃. The arrange sequence of diffusion layers is different at varied temperature in the zone marched with Al,Cu and Mg, so is the formation mechanism of these diffusion layers. It has been shown that stress plays a great role in the diffusion process at low temperature. The formation of Mg/Al interfacial transition zone experience four stages, the sequence of forming diffusion layers is as follow: MgAl→Mg₃Al₂→Mg₂Al₃. The formation mechanism of intermetallic compound, which is under a condition that elements are in solid-liquid transformation state, is different from the one in solid state,so the quatity of intermetallic compound emerge near the interface may be different.