Thermal fatigue crack behavior of SiCp/A356 composites prepared by stirring casting

摘要

Graphical abstract Display Omitted Highlights ? A Step-Like Propagation Model (SLPM) is proposed to reveal the thermal fatigue crack growth process. ? The thermal fatigue crack propagated along the interface of particle and went through the matrix. ? The micro crack generated in the interface of particle and matrix after many heating and cooling cycles and accelerate the growth of crack. ? The fracture surface of the crack growth presents a step shape, including the platform and the jump period. Abstract The thermal fatigue crack initiation and propagation behavior of SiCp/A356 composites which is produced by stirring casting were studied. Specimens with a V-shaped notch were used in the thermal fatigue experiment. Optical microscope (OM) and scanning electron microscope (SEM) were used to observe the crack growth. Crack initiated at the notch tip after about 150 cycles of heating and cooling from room temperature to 250°C. The crack propagation stage was dominated during the whole crack growth. Cracks mainly propagated along the interface of particle and through the matrix. The propagation stage experienced the cycle of slow propagation and fast propagation, and a Step-Like shape was observed during the crack growth process. The micro cracks appeared in the interface of particle and the matrix after repeated thermal cycles, and induced fast propagation by coalescing with the main cracks. Distributions of the particle play an important role in hindering thermal fatigue crack propagation. Hardness of the composites decreased with the increase of the number of cycles, and decreased by 46.1% after thermal 290 cycles.