Remelting and bonding of deposited aluminum alloy droplets under different droplet and substrate temperatures in metal droplet deposition manufacture

• The influence of interfacial temperature on the remelting and bonding of droplets was investigated.
• The surface temperature at the top of the deposition column was calculated and predicted.
• The thermal process of droplet deposition component was simulated.
• The appropriate combination of Tdrop and Tb was determined.

Micro-void and cold lap are the most common defects of 3D components in aluminum alloy droplet deposition manufacture, which have been found to be associated with the poor remelting and metallurgical bonding between droplets under inappropriate droplet and substrate temperatures. To address this problem, the appropriate temperature condition for achieving good metallurgical bonding between droplets was analyzed and the relationships among surface temperature (Tsurf), substrate temperature (Tb), droplets temperature (Tdrop), droplets deposition frequency (f) and height of deposition layer (h) were estiblished by one-dimensional (1D) heat transfer analytical model. On this basis, a three-dimensional (3D) transient finite element mode was developed to simulate the thermal behavior during metal droplet deposition component using element birth and death technology. The distribution and variation of surface temperature of previously deposited droplets (Tsurf) were predicted and analyzed under different process parameters in fabricating aluminum alloy 3D components. And then, a series of deposition experiments were conducted with different droplet temperatures (Tdrop) and substrate temperatures (Tb). The experimental results show that the good remelting and metallurgical bonding between droplets were obtained with the appropriate combination of Tdrop (700 °C) and Tb (450 °C). The micro-void and cold laps were not observed in the interior of formed samples, indicating that experimental results basically agree with the theoretical analysis and simulation results. The work provides a useful theoretical and experimental guide for metal droplets deposition manufacture.