Effect of microstructure evolution on high cycle fatigue behavior of brass

The fatigue behavior and the microstructure of brass induced by HCF test are investigated systematically. The fatigue fracture morphologies are characterized by SEM. The microstructures are analyzed by OM and TEM. It is found that crack initiation of brass is accompanied by micro-cracks. In crack propagation region and final fracture region, secondary cracks and the dimples can be observed, respectively. The number of the twins increases, which can be attributed to the plastic deformation when brass subjects to HCF test. A series of change in dislocation structures refines the original grains into sub grains by forming new boundaries in the original grains. In addition, uneven microstructure distribution in the process of cyclic loading causes stress concentration, which generates the PSBs turned into preferential cracking initiation. The high cycle fatigue fracture mechanism of brass induced by dislocation structure evolution is proposed finally.