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.