Elasto-plastic deformation within diamond reinforced metals for thermal management

Diamond reinforced metals are being developed for use as highly sophisticated heat spreading material in power electronics or satellite laser optics. These particle reinforced composites combine the excellent thermal properties of diamond with a metal matrix, which enables shaping and joining onto the components. The mismatch in thermal expansion and Young's moduli of matrix metal and diamond reinforcement is responsible for high micro stresses under operational conditions of thermal cycling. These stresses may lead to interface delamination and/or matrix damage degrading the initially good thermal properties. Therefore, the interface bonding strength and the deformability of the matrix determine the quality of such metal matrix composites. Aluminum is favored as matrix metal due to its high ductility and carbide forming ability on diamond surfaces, which significantly improves the interface bonding strength. Silver offers high thermal conductivity and alloying with silicon produces reactivity with diamond, giving strong bonding strength. The tensile behavior of both composites was investigated by non-destructive in-situ neutron diffraction and acoustic emission (AE) measurements. Post mortem scanning electron microscopy reveal the bonding quality of the composites correlated to the reinforcement architecture and the plasticity of the matrices. Conclusions on the elasto-plastic deformation behavior of the investigated composites for thermal management application are drawn. (C) 2016 Published by Elsevier B.V.