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A STUDY OF THE GROWTH OF VOIDS IN COPPER DURING THE CREEP PROCESS BY MEASUREMENT OF THE ACCOMPANYING CHANGE IN DENSITY
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1961
Year
Single CrystalsEngineeringSevere Plastic DeformationCreep CurveMechanical EngineeringVoid GrowthWork HardeningMicrostructure-strength RelationshipSolidificationMaterials ScienceMaterials EngineeringStrain LocalizationMetallurgical InteractionSolid MechanicsPlasticityMicrostructureDislocation InteractionApplied PhysicsMetallurgical ProcessMetallurgical SystemMechanics Of Materials
A study was made of the change in density during the first (transient) and second (linear) stages of the creep curve of polycrystalline copper as a function of stress, temperature, plastic strain, impurity and atmosphere effects, and structure, including single crystals. Voids did not grow in single crystals strained 15% at 500 deg C, or in a polycrystalline aggregate produced by recrystallizing a single crystal. It appeared that voids are heterogeneously nucleated at grain boundaries by an insoluble phase, or phases, which can be removed by directional solidification. The principal controlling mechanism of void growth appesred to be condensation of vacancies at grain boundaries. Vacancies are transported to a boundsry snd condense as a consequence of the tensile stress component across the boundary, which depends on the orientation and configuration of the boundary plane and on boundary shear across ledges and other irregularities. The ultimate source of vacancies is the free surface and diffusional transport is by way of the boundary plane. (auth)