Effect of cold flakes on mechanical properties of aluminium alloy die casts

Abstract

The cold flake was detected in aluminium alloy die casts ADC12 by using the scanning acoustic microscope, and was visualised in the acoustic image as bright and dark regions, which were corresponding to the oxide layer and the body of the cold flake respectively. By using the specimen which contains the cold flake, the tensile testing and the fatigue testing were carried out. The in process ultrasonic measurement was also carried out with a water bag in the fatigue testing to detect detachment of the cold flake from the matrix in the fatigue process. From these results, it was found that the cold flake was detached from the matrix in the fatigue process to form a crack, and cold flakes, especially exposed cold flakes, reduce the tensile strength and the fatigue life of die casts. The effect of the cold flake on the strengths was discussed from the point of crack propagation.