Time-dependent failure of silver interlayer welds
Silver interlayer diffusion welds exhibit very high tensile strengths, despite the soft interlayer, because of the constraint provided by the stronger base metals. However, despite the high tensile strength, diffusion-welded-silver joints undergo time-dependent failure, or creep rupture at relatively low tensile stresses at ambient temperature, apparently by a ductile microvoid-coalescence mechanism at the coated and welded interfaces. Two classes of time-dependent tensile failure were investigated. In the first case, the applied stress does not produce any plastic deformation in the base metal, and rupture appears to be controlled by time-dependent plasticity within the silver interlayer as a result of the effective stress in the interlayer. The plasticity causes cavity nucleation and, eventually, coalescence and rupture. In the second case, time-dependent plasticity is observed in the base metals, and concomitant shear occurs within the soft silver interlayer under a high triaxial stress state. Here, the time-dependent plasticity of the base metal accelerates rupture. These models were substantiated by analyses of the stress and temperature dependence of the rupture times, finite-element analysis of the stress state within the interlayer, and microscopy of the fracture surfaces and interfaces loaded to various fractions of the expected rupture times. The procedures for preparing silver interlayers by planar-magnetron sputtering were developed in this research. This process was preferred over other interlayer fabrication methods, such as brazing, electrodeposition, and other physical vapor deposition processes, because of the more reproducible results obtained using planar-magnetron sputtering. The findings of this research, however, are applicable to joints in which the interlayers are prepared by these and other processes. 79 refs., 72 figs., 4 tabs.
- Research Organization:
- Lawrence Livermore National Lab., CA (USA)
- Sponsoring Organization:
- DOE/DP
- DOE Contract Number:
- W-7405-ENG-48
- OSTI ID:
- 6990167
- Report Number(s):
- UCRL-53945; ON: DE90008015
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
360101* -- Metals & Alloys-- Preparation & Fabrication
360102 -- Metals & Alloys-- Structure & Phase Studies
360103 -- Metals & Alloys-- Mechanical Properties
ACTINIDES
ALLOYS
ALUMINIUM ALLOYS
ALUMINIUM BASE ALLOYS
ANNEALING
AUSTENITIC STEELS
CHROMIUM ALLOYS
CHROMIUM-NICKEL STEELS
COATINGS
CORROSION RESISTANT ALLOYS
CREEP
CRYSTAL STRUCTURE
DEPLETED URANIUM
DIFFUSION WELDING
DIMENSIONS
ELEMENTS
FABRICATION
FAILURES
FINITE ELEMENT METHOD
HARDNESS
HEAT RESISTANT MATERIALS
HEAT RESISTING ALLOYS
HEAT TREATMENTS
HIGH ALLOY STEELS
IRON ALLOYS
IRON BASE ALLOYS
JOINING
JOINTS
MATERIALS
MECHANICAL PROPERTIES
METALS
MICROSTRUCTURE
NICKEL ALLOYS
NUMERICAL SOLUTION
PLASTICITY
RUPTURES
SILVER
STAINLESS STEEL-304
STAINLESS STEELS
STEEL-CR19NI10
STEELS
TEMPERATURE DEPENDENCE
TENSILE PROPERTIES
THICKNESS
TRANSITION ELEMENTS
URANIUM
WELDED JOINTS
WELDING