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Metallographic Study of Laser Thermal Fatigue Damage on Piston

The experiments of thermal fatigue damage on piston were conducted by shaped high power laser. Microstructure of thermal fatigue damaged specimen was characterized by scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS). The mechanical properties of thermal fatigue specimen were evaluated by microhardness and the corresponding damaged mechanisms were discussed. The results show that cracks originated from the interface of Al-matrix and intermetallic phase due to the thermal and mechanical mismatch between the brittle components of the microstructure and the surrounding ductile matrix. Oxides of thermal fatigue crack can accelerate the damage of piston. There exists a decline tendency in the microhardness of piston at all locations after thermal fatigue tests due to the comprehensive effects of nonequilibrium distribution of temperature and cooling method.