Transient liquid phase bonding mechanism and mechanical properties of magnesium alloys based on spark plasma sintering welding

This study investigates the microstructure and mechanical properties of ZM51 Mg alloy joints fabricated by spark plasma sintering (SPS) joining using a Zn interlayer. The joints were produced at four different brazing temperatures (300 °C, 320 °C, 340 °C, and 360 °C) with applied pressure. At 340 °C, a single-layer structure joint consisting of a Mg 7 Zn 3 layer with finely dispersed MgZn 2 was formed, presenting the highest shear strength of 84.14 MPa. A control experiment using pure Mg (Mn-free) substrates shows that without Mn, no MgZn 2 forms and the strength drops to 46.04 MPa, confirming that Mn is essential for the observed microstructure. The bonding mechanisms at different temperatures are presented: lower temperatures lead to incomplete diffusion and multi-layer structures, while higher temperatures promote excessive MgZn 2 formation and interfacial oxidation. This study demonstrates that SPS joining at 340 °C enables flux-free, low-temperature fabrication of high-strength Mg alloy joints via transient liquid phase bonding, with Mn playing a critical role in microstructural evolution.