Effect of Temperature, Heating Rate, and Cooling Rate on Bonding and Nitriding of AlSi10Mg Powder Occurring During Supersolidus Liquid-Phase Sintering

This study investigated the effect of supersolidus liquid-phase sintering conditions on the powder particle bonding and the AlN-phase formation of an AlSi10Mg alloy. Sintering was conducted at temperatures between 550 and 579 °C, with a holding duration of 2 h under a nitrogen atmosphere. The sintering cycles included four heating segments, performed at rates ranging from 0.2 to 5 °C/min for a total of between 5 and 15 h, and a cooling segment performed at two different cooling rates, 0.15 and 5 °C/min, resulting in durations of 12 and 70 h, respectively. Three powder batches exhibiting different particle size distributions were tested. An X-ray diffractometer, optical microscopy, and scanning electron microscopy were used to characterize phase formation and particle bonding. The results show that higher sintering temperatures and faster heating/cooling rates led to a lower fraction of AlN. In contrast, lower sintering temperatures or slow heating promoted the development of a thicker AlN shell around powder particles, inhibiting the bonding of the AlSi10Mg powder and preventing densification via the sintering process. These findings suggest that sintering at temperatures between 570 and 575 °C, with heating and cooling rates of at least 2 °C/min, constitutes a more favorable window for the densification of AlSi10Mg under a nitrogen atmosphere.