A novel suppressing evaporation method for enhancing micro-complex magnesium alloy parts additive manufacturing

The increasing demand for micro-complex and customizable magnesium (Mg) alloy structures presents significant challenges for additive manufacturing (AM), particularly in controlling porosity and achieving high-dimensional accuracy. These challenges arise from bubble entrapment and explosive events caused by intense Mg evaporation. This study, for the first time, elucidates the fundamental mechanism underlying these defects, identifying spontaneous bubble nucleation and subsequent explosions within the melt pool as the root cause. In metal droplet-based AM (MDBM), experiments demonstrate that larger bubbles destabilize droplets and disrupt deposition trajectories due to intensified energy release, ultimately degrading print quality. To address this issue, a bubble nucleation and growth model, independent of specific Mg alloy AM methods, was developed. Based on this model, a novel strategy was proposed to mitigate Mg evaporation-induced defects. By identifying a critical bubble nucleation temperature, it was established that operating below this threshold completely suppresses bubble nucleation, thereby preventing associated defects. For conditions exceeding this temperature, the bubble growth model enables precise regulation of bubble size through process parameter optimization, effectively minimizing defects and enhancing structural integrity. As a result, the fabricated structures exhibit high dimensional precision and superior mechanical performance, characterized by pore-free microstructures, minimal dimensional deviation, and enhanced mechanical properties. This study introduces a parameter-driven method for suppressing Mg evaporation-induced defects across various Mg alloy AM technologies, with potential applicability to other highly evaporative metal AM processes. Moreover, it represents the first successful fabrication of micro-complex structures using highly evaporative metals, expanding the material selection for MDBM.