Effect of Holding Time on Microstructure and Mechanical Properties of Diffusion-Bonded Mg1/Pure Ag Foil/1060Al Joints

Mg1 and 1060 Al were diffusion-bonded by using pure silver foil under different holding times (10 min~120 min). The interface of the joint consists of Mg-Ag diffusion zone, Ag foil interlayer and Ag-Al diffusion zone. The distributions of Mg, Ag and Al show ladder-like distributions at the interface of the joints. When the holding time is below 90 min, silver foil has impeded the inter-diffusion of Mg and Al. When the holding time is beyond 90 min, the brittle eutectic Mg-Al intermetallic compounds (IMCs) cannot be avoided. Mg3Ag and MgAg intermetallic compounds formed on Mg base side. Ag2Al intermetallic compound grew on Al base side. The thicknesses of Mg3Ag, MgAg and Ag2Al increased linearly with the increasing holding time, which is contrary to that of the silver foil. The growth rate relationship of the formed IMCs is MgAg > Ag2Al > Mg3Ag according the slope values of the fitted lines. The hardness sharply increased at the interface because of the formation of IMCs. The maximum hardness values of three IMCs Mg3Ag, MgAg and Ag2Al are 287.5 HV, 196.5 HV and 175.7 HV respectively. The hardness of each IMC layer increased with the extension of holding time. The shear strength of the joints decreased from 10.5 MPa to 4.6 MPa with the rising holding time.