Investigation on the microstructure and fracture behavior of super-eutectic ZA alloy welded joint by pulse fiber laser

다국어 초록 (Multilingual Abstract)

In this study, we present the experimental laser welding of super-eutectic ZA alloy. Microstructures of the ZA alloy′s bond area welded by pulsed laser were investigated using an optical microscope, scanning electron microscope, energy diffraction spectrum and X-Ray diffractometer. The results showed that microstructures in the weld mainly consisted of threadlike columnar crystals, coarse dendrites and fine equiaxed grains. Secondary particles were produced in the interdendritic zones because of the composition segregation. A poor Al area was formed inside the η grain while a rich Al area takes shape outside the η grain. The occurrence of the composition segregation can increase the grain boundary cracking tendency. The existence of a large number of η phase greatly intensified the brittle of this material. The presence of many cleavage steps in the fractograph principally depended on the secondary cleavage effect between two cleavage cracks on different planes. The evolution of cracks along the twinning plane was the result of the secondary cleavage substituting for the twinning deformation in the vicinity of the crack tip.