Influence of Heat Treatment on High-Cycle Fatigue and Fracture Behaviors of Piston Aluminum Alloy Under Fully-Reversed Cyclic Bending
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In the present article, the influence of the heat treatment on high-cycle fatigue and fracture behaviors of piston aluminum–silicon alloys was studied. For this objective, standard samples were tested under fully-reversed cyclic bending by a rotary fatigue machine and then, fracture behaviors were investigated by the field emission scanning electron microscopy. Before experiments, two heat treatments were performed on as-cast aluminum specimens, including a cooling process on samples after casting and the T6 treatment (solutioning for 5 h at 500 °C, quenching and ageing for 9 h at 180 °C). Obtained results showed that the heat treatment changed the distribution and the size and of silicon phases in the aluminum matrix and increased the hardness, significantly. In addition, the high-cycle fatigue lifetime increased by the heat treatment, surprisingly as 2146% and 411%, at the highest stress level and the lowest stress level, respectively. This enhancement was more than the improvement by cooling samples after casting. Observing cleavage and quasi-cleavage marks on the specimen fracture surfaces was the reason for the brittle fracture behavior. Besides, cleavage planes were smaller in heat treated samples, with shorter micro-cracks or lower crack densities, which affected the fatigue lifetime of the material.
KeywordsHeat treatment effect Aluminum–silicon alloy Engine piston High-cycle fatigue Fracture behavior
Authors would tend to thank Motorsazi Pooya Neyestanak (MPN) Company, in Isfahan, Iran for their financial supports, in addition to provide raw materials and to perform the casting process.
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