Thermal shock property of hyper eutectic Al-20 to 50%Si alloy castings with refined primary silicon

Abstract

Especially high silicon containing Al-Si alloy castings were tried to refined of primary silicon crystals. The melt were treated by flux included phosphorus. Even primary silicon of the Al-50%Si alloy was also able to refined, and its sizes were under 150μ, and yet primary silicon sizes of other alloys were about 100μ at 40%Si, 70μ at 30%Si, and 30μ at 20%Si.
Al-(2050%) Si alloys were tested with thermal shock. The specimen of column shape with 23mm dia; 23mm height were quenched into ice water bath after heated at 500°C for 20min. This treatment was repeated until 500 cycles. Deformation of specimen was reduced with increasing of silicon content. Simultaneously hair cracks occured at all round of specimen and it expanded. But 2025%Si alloys of lower silicon content deformed largely. Therefore Al-(3035%) Si alloys showed excellent thermal shock resistance, that is to say, deformation was small and break out cracks were scarcely.