Effect of cooling rate on the mechanical properties of AC4CH aluminum alloy castings

Abstract

The cooling rate in a range of 3.3 to 12.1K/s was measured in 3 to 15mm thick castings. The tensile properties are improved with higher cooling rate. The marked effect of cooling rate on the dendrite structure is clearly observed, and the linear relation between the dendrite arm spacing and the cooling rate is found. The increased cooling rate refines the size of eutectic silicon particles but it dose not influence the spheroidization of these particles. The concentration of magnesium in the matrix increases especially with higher cooling rate in the state of solution treatment. The improvement of tensile properties are attained by the increasing of precipitates due to higher magnesium concentration in the matrix and of refined eutectic silicon particles.