Abstract
To investigate the fatigue properties of aluminum alloy die castings , fatigue tests were conducted on five types of aluminum alloy die castings. The fatigue strengths were evaluated by using the stair case method for small sample size (JSME Standard S02-1994 14S-N testing method ) and √<area> parameter model using the statistics of extreme values of casting defects. The main results obtained are as follows: (1) For ADC10, ADC12, and D10FM, the origin of fatigue crack is casting defect caused by various die casting methods. While for ADC24Z and AC4C, the origin of fatigue crack is the base matrix. (2) In the case of ADC10, ADC12, and D10FM, the square root of casting defect area (√<area>) follows the statistics of extreme values, and the fracture surface at around the fatigue crack initiation portions were Mode I fracture surface. The fatigue limits predicted by the √<area> parameter model are in good agreement with the fatigue limits from the 14S-N testing method. (3) In the case of ADC24Z , the fatigue fractures were caused by Mode I cracks. (4) In the case of AC4C, the fatigue fractures were caused by Mode II cracks. (5) The extra-long fatigue strength(10^7-10^9 cycles)of AC4C-T6 decreased along with the increase in the number of cycles, while the extra-long fatigue strength(10^7-10^9 cycles) of ADC10-T5did not decrease along with the increase of the number of cycles.
