The Study Of Properties For A357 Casting Aluminum Alloy

The properties of tension and fatigue for A357 casting aluminum alloy at room temperature and 150℃temperature are studied. The fatigue load is sinusoidal wave form with frequency of 40Hz, stress ratios, r, are of -1, 0.05 and 0.4 respectively. The morphology of fracture surfaces and fracture mechanism are observed and analyzed by scanning electric microscope (SEM). The experimental results show that the tensile strength, proof stress, elongation and sectional shrinkage of A357 casting aluminum alloy at T5 heat treatment are larger than that at T6 heat treatment at room temperature. At 150℃high-temperature, compared to T6 heat treatment, the elongation and sectional shrinkage of A357 casting aluminum alloy at T5 heat treatment increase, but the tensile strength and proof stress decrease. At T5 heat treatment, the tensile strength, proof stress and elongation of A357 casting aluminum alloy at room temperature are larger than that at 150℃high-temperature, while at T6 heat treatment, the tensile strength and elongation of A357 casting aluminum alloy at room temperature are larger than that at 150℃high-temperature, but proof stress of A357 at room temperature is less than that at 150℃high-temperature.The fatigue strengths of A357-T6 casting aluminum alloy are 70MPa for r=-1 , 95MPa for r=0.05, and 135MPa for r=0.4 respectively at room temperature, while 75MPa for r=-1 and 100MPa for r=0.05, respectively at 150℃high-temperature. The fatigue strengths of A357-T6 casting aluminum alloy increase with increasing stress ratio at both of temperatures. The temperature effects on fatigue strength of A357-T6 casting aluminum alloy have not been seen at same stress ratio. The temperature effects on tension fracture surface and fatigue fracture surface of A357-T6 casting aluminum alloy have not been seen yet. A357-T6 casting aluminum alloy has good plastics because of dimple on tension fracture surface. Fatigue stripe, Si particles and holes because of debonding of Si particles have been seen on fracture surfaces, that shows fatigue crack propagation along dendrite boundary. Fatigue cracks initiate from inclusion or casting defects at sub-surface.