抄録
An AC4CH aluminum casting alloy was solution-treated using high-frequency induction heating apparatus, and effects of solution treatment on micro-structural features and mechanical properties were investigated. The results were as follows. (1) Investigation of the heated state of the specimen revealed no significant temperature distribution both in the length and width directions of the specimen when the specimen was set at the optimum position in the heating coil. (2) When the AC4CH alloy was solution-treated at temperatures ranging from 450°C to 570°C, under the conditions of heating rate of 40.0°C/s and solution time of 0min, no obvious changes in the size and morphology of the eutectic Si particles were recognized. In contrast, hardness and proof stress increased with rising solution temperature. (3) The aspect ratio of the eutectic Si particles and electrical conductivity of the AC4CH alloy solution-treated at 560°C decreased until the solution time of 3min and then saturated, whereas the size of the eutectic Si particles increased gradually with the lapse of solution treatment time. The hardness and proof stress of these samples increased due to solid solution hardening expected from the change of electrical conductivity. (4) When solution treatment was carried out at heating rates ranging from 0.4°C/s to 40.0°C/s, there were no changes in the electrical conductivity, hardness, and proof stress. However, growth of the eutectic Si particles was suppressed at the heating rate of 40.0°C/s.
