Effect of Process Parameters on Microstructure and Shear Property of Diffusion Bonded Joints of Mg-9Gd-4Y-2Zn-0.5Zr Alloy

The vacuum diffusion bonding tests were carried out on forged Mg-9Gd-4Y-2Zn-0.5Zr alloy at different temperatures （420‒510 ℃）, pressures （2‒6 MPa） and time periods （2, 8 h） with a spark plasma diffusion bonding equipment with rapid pulse current heating. The effect of process parameters on the microstructure and shear property of the joints was studied. The results show that the edge area of the joints exhibited a honeycomb-like porous structure, and the central area of the joints had no obvious defects such as pores. With the increase of diffusion bonding temperature, the block LPSO phases in the joints decreased, the lamellar LPSO phases increased, the unwelded area of the bonding interface decreased, and the shear strength of the joints increased; when the temperature was raised from 480 ℃ to 510 ℃, the shear strength of the joints was basically unchanged. At temperatures not higher than 450 ℃, with the increase of diffusion bonding pressure, the unwelded area of the bonding interface decreased and the shear strength of the joints increased. At temperatures higher than 450 ℃, with the increase of diffusion bonding pressure, the morphology of the bonding interface did not change, and the joints obtained high shear strength under the pressure of 2 MPa. With the extension of diffusion bonding time period, there was no obvious change in the morphology of the bonding interface, and the shear strength of the joints was basically unchanged. At the temperature of 510 ℃, pressure of 2 MPa and time period of 2 h, the bonding interface was completely welded and the shear strength reached 94.8% of that of the base material （115 MPa）.