Extra Long Life Fatigue Properties of Aluminum Die Casting Materials
Koji YAMADA and Susumu MIYAKAWA
Abstract:To investigate the extra long life fatigue properties of aluminum die casting materials, fatigue tests were conducted on two type of aluminum die casting materials. One type is Al-Si-Cu die casting alloys ADC10-T5 and the other is Al-Si-Mg die casting alloys AC4C-T6. The main results obtained are as follows, (1)For ADC10-T5, the origin of fatigue crack is casting defect and the fracture surface at around the fatigue crack initiation portions were Mode‡Tfracture surface. (2)For AC4C-T6, the origin of fatigue crack is the base matrix and the fracture surface at around the initiation portion changed from Mode‡Tfracture surface to Mode‡U fracture surface along with the increase in the number of cycles. At the range of Nfƒ105 or about Nf=105, fracture surface were Mode‡Tfracture surface, about Nf=106, fracture surface were mixture of Mode‡Tand Mode‡U fracture surface, and at the range of Nf„107, fracture surface were Mode ‡Ufracture surface. (3)The extra long life fatigue strength(107|109 cycles) of AC4C-T6 decreased along with the increase in the number of cycles, while the extra long life fatigue strength(107|109 cycles) of ADC10-T5 did not decrease along with the increase of the number of cycles. (4)The casting defect size in non-fracture specimen was much smaller than the allowable defect size predicted by the ãarea parameter model. It seems to be that the reason why no reduction was recognized in the fatigue strength of the ADC10-T5 in the life range beyond 107 cycles. Key Words:Aluminum die casting materials, Extra long life fatigue properties, Mode‡Tfracture surface, Mode‡Ufracture surface ãarea parameter model