Corrosion Fatigue Crack Propagation in Squeeze-Cast Al-Si Aluminum Alloy

To clarify the behavior of corrosion fatigue crack propagation in squeeze-cast Al-Si aluminum alloy, AC8A-T6, corrosion fatigue crack propagation tests were performed in this investigation under the condition of the stress ratio of 0.1, triangular waveform and a testing frequency of 10Hz in 3.0% saline solution using compact tension specimens with side grooves. Judging from the experimental results, corrosion fatigue crack propagation behavior is affected by the initial stress intensity factor range, ΔK, at the start of the experiment. When the test was started at low ΔK, the crack propagation rate was enhanced immediately after starting the test and thereafter became retarded, compared with that in air. It was observed that the retardation of crack propagation is due to blunting by the secondary cracks. On the other hand, enhancement of crack propagation is caused by dissolution around the eutectic silicon. The path of crack propagation during corrosion fatigue depended on the microstructure of material which consisted of dendrite and eutectic spheroidal silicon. Corrosion fatigue cracks propagated mainly along the eutectic structure and deviations in the path were larger than those under the test in air.