Abstract: Annealing has an important influence on the interface microstructure of heterogeneous connecting components, and determines the strength and performance of the connection. The annealing process of magnesium/aluminum alloy thick-to-board bonded plates formed by extrusion is studied. The results show that the annealing treatment transforms the transition layer from a single layer to a double layer structure, which are made up of γ-Al₁₂Mg₁₇ sub-layer and β-Al₃Mg₂. The annealing temperature is 250 ℃, the transition layer width grows gently from 20μm to 30 μm with time, and the grain size of the magnesium side matrix increases to 11.73 μm. When annealing time is 1 h, the transition layer width increases from 15 μm to 45 μm as the temperature increases; The grain size of the magnesium side matrix structure shows a trend of decreasing at and then increasing. Moreover, low-temperature and short-time annealing will increase the interface bonding strength, up to about 60 MPa. But with the increase of annealing temperature and time, the interface bonding strength and micro-hardness decreased, it provides a theoretical basis and scientific guidance for the extrusion and manufacturing of high-performance magnesium/aluminum alloy thick-direction bonded plates.

Key words: thick to combine board, extrusion, annealing, interface structure, micro-structure