IN-SERVICE LOADING OF ALSILL ALUMINUM CAST ALLOY IN THE VERY HIGH-CYCLE REGIME

The fatigue properties of two AlSi11 cast alloys as used for car wheel s have been tested in the regime of 10(8)-10(9) cycles. An AlSi11 alum inium alloy with 0.12-0.20% Mn and one with 0.05% Mn and increased H-2 content during the pouring procedure are compared. It is shown that m ainly cast voids determine the fatigue properties. These material inho mogeneities reduce the fatigue strength and lead to early fracturing. The number of cycles to failure decreases with increasing void cross-s ection. With a statistical analysis of the fatigue data, it is shown t hat the mean number of cycles to failure is higher for the alloy with fewer large cast voids and a higher Mn content. This alloy is less sus ceptible to cast voids, and the threshold stress intensity value is ap proximately 10% higher.