SLIP DEFORMATION AND FRACTURE OF DIRECTIONALLY SOLIDIFIED DZ-38G SUPERALLOY

Directionally solidified DZ-38G superalloy was in situ observed under SEM in order to obtain a better understanding of its slip deformation and fracture process. The slips initiate in matrix and eutectic, and they are able to be transmitted by the eutectic. The slips on dendrite arms are much obvious than those in the interdendritic areas. The slip direction may slightly alter with the change of columnar grain orientation. The microcracks are prone to initiate at transverse grain boundarie, carbides on grain boundaries or eutectic/matrix interfaces. A microcrack usually propagates along a zig-zag path, and it is controlled by the maximum shear stress and tensile stress. The propagation of cracks is closely related to the straightness of columnar grain boundaries.