An Investigation of High Cycle Fatigue Behavior of Magnesium Alloy for Cylinder Head Application

This paper investigates the high cycle fatigue behavior of the AZ91 magnesium alloy. The feasibility study of replacing this alloy with the A356 aluminum alloy for a diesel engine cylinder head is discussed. For this purpose، the AZ91 alloy was casted in a permanent mold and the microscopic examination with optical and scanning electron microscopes (SEM) and mechanical tests include tensile، hardness and high cycle fatigue tests were performed on samples which were prepared based on standards. Results are compared to the A356 aluminum alloy. High cycle fatigue tests were carried out at a stress ratio (R) of -1 and a frequency of 50 Hz at room temperature in the air. The microscopic investigation demonstrates that the microstructure composed of alpha and beta (Mg17Al12) phases. Fatigue test results show that the fatigue strength of the AZ91 alloy is lower than the A356 alloy، but still in the range of required values for the application in cylinder heads.