Modeling of thermal stresses in a graded Cu/W joint

Thermally induced stresses and strains in a CuCrZr alloy-W joint are analyzed using finite element methods. The effect on stress and strain of using different materials as interlayers to join CuCrZr to W is examined and compared to geometries without an interlayer (sharp interface). Oxygen free high conductivity copper (OFHC) and several types of graded structures formed with OFHC and W are used as the different interlayer materials. Temperature dependence of the properties in addition to plasticity and strain hardening are considered in the finite element formulation. The use of an OFHC Cu interlayer results in the maximum reduction of stress compared to the sharp interface, but also in large highly localized plastic strains that increase under operation conditions. The residual stress is slightly higher for OFHC/W graded interlayers, but still significantly lower than for the sharp interface. However, a notable difference for the graded interlayers is that the plastic strain is greatly reduced compared with the OFHC interlayer