Mechanism of plastic damage and fracture of a particulate tungsten-reinforced copper composite: A microstructure-based finite element study

摘要

Tungsten particle-reinforced copper composites offer a unique combination of conductivity and strength for high-temperature heat sink applications. Particulate tungsten reinforcement leads to a strong enhancement of strength below 300°C while the ductility is significantly decreased on the other hand. Above 500°C, the reinforcing effect disappears completely and the ductility is further reduced. The composite exhibits a considerable scattering in the tensile elongation. The aim of this computational study is to understand the deformation and fracture behavior of the composite on the basis of its microstructure. To this end, we employed a microstructure-based finite element analysis using a dedicated micrograph mapping tool OOF. The material parameters required for damage modeling were calibrated by fitting the simulated tensile curve into the measured one. A simulation of tensile loading case at 300°C revealed the characteristic development of plastic strain localization forming a narrow deformation band. Such a localized plastic yield pattern occurs as a result of von-Mises stress concentration in this band. Hydrostatic tensile stress is also concentrated in the same band leading to initiation and accumulation of ductile damage and finally to cracking. The scattering in the final rupture strain is shown to be a consequence of the random microstructure. The local configuration of the phase morphology turns out to play an important role in triggering the strain localization. The pronounced impact of test temperature on yield stress and rupture strain is attributed to the presence of thermal stress produced by thermal expansion mismatch upon heating.