In-situ Study On Deformation Behavior And Mechanism Of GH4742 In Different Microstructure States

GH4742 alloy is widely used in the preparation of turbine discs and gas turbine wheels of aviation and aerospace engines due to its excellent high temperature mechanical properties,but in the process of processing GH4742,mixed crystals that affect the performance of products are prone to occur,and the influence of GH4742 mixed crystals on the plastic deformation coordination mechanism is conducive to providing support for process control with the goal of uniform structure.In this paper,the deformation behavior,fracture mechanism,microstructure evolution and deformation mechanism of mixed and homogeneous GH4742 alloys during deformation were studied by scanning electron microscopy and in situ tensile test under EBSD.During the deformation process,the dislocation slip of most grains in the two states GH4742 conforms to Schmid’s law,that is,it is activated in the larger SF value slip system;Some grains are activated by the influence of surrounding grains in a small SF value slip system.In addition,except for the case where the slitting stress of the grain itself is greater than the critical slitting stress,and its internal slip system is activated;When slip transport(direct or indirect)occurs between grains,slip systems are also activated inside the grains.With the increase of deformation,the small-angle grain boundaries of GH4742 in the two states increased,and the small-angle grain boundary growth of the fine grain region of mixed GH4742 was approximately 3 times that of the coarse grain region.During the deformation process,there are four rotation types in the two states GH4742,which are not in good agreement with the theoretical rotation model,but the consistency between the uniform GH4742 and the Taylor model is higher than that of the mixed state,indicating that the stress difference between the grains of the uniform GH4742 is smaller than that of the mixed GH4742.With the increase of deformation and the increasing number of slip traces,MC carbides play an important role in the fracture process of GH4742 in the two states,and microcracks will be formed when the carbides themselves are broken and the carbides are debonded from the matrix.Among them,the self-broken carbides are mostly long strips,while the debonded carbides from the matrix are mostly ellipsoidal.Both states GH4742 belong to plastic fractures,and the fractures are microporous polymerization type;The presence of carbides between cracks indicates that carbides provide favorable conditions for crack propagation.With the increase of deformation,the average KAM value increases,that is,the overall deformation degree intensifies.The standard deviation of KAM value of mixed GH4742 is always greater than that of uniform GH4742,that is,the deformation coordination of mixed GH4742 is worse than that of uniform GH4742.