Time-dependent failure of silver interlayer welds

Technical Report · Thu Feb 01 00:00:00 EST 1990

DOI:https://doi.org/10.2172/6990167· OSTI ID:6990167

Rosen, R. S.

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. (LLNL), Livermore, CA (United States)
• Sponsoring Organization: DOE/DP
• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 6990167
• Report Number(s): UCRL-53945; ON: DE90008015
• Resource Relation: Other Information: Thesis (Ph.D.)
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM BASE ALLOYS
DIFFUSION WELDING
DEPLETED URANIUM
STAINLESS STEEL-304
WELDED JOINTS
FAILURES
ANNEALING
COATINGS
CREEP
FINITE ELEMENT METHOD
HARDNESS
MICROSTRUCTURE
PLASTICITY
RUPTURES
SILVER
TEMPERATURE DEPENDENCE
TENSILE PROPERTIES
THICKNESS
ACTINIDES
ALLOYS
ALUMINIUM ALLOYS
AUSTENITIC STEELS
CHROMIUM ALLOYS
CHROMIUM-NICKEL STEELS
CORROSION RESISTANT ALLOYS
CRYSTAL STRUCTURE
DIMENSIONS
ELEMENTS
FABRICATION
HEAT RESISTANT MATERIALS
HEAT RESISTING ALLOYS
HEAT TREATMENTS
HIGH ALLOY STEELS
IRON ALLOYS
IRON BASE ALLOYS
JOINING
JOINTS
MATERIALS
MECHANICAL PROPERTIES
METALS
NICKEL ALLOYS
NUMERICAL SOLUTION
STAINLESS STEELS
STEEL-CR19NI10
STEELS
TRANSITION ELEMENTS
URANIUM
WELDING
360101* - Metals & Alloys- Preparation & Fabrication
360103 - Metals & Alloys- Mechanical Properties
360102 - Metals & Alloys- Structure & Phase Studies