The present study aims at elaborating innovative copper based composite plates with a graded microstructure and thereby evolutive mechanical, thermal, electrical and wear properties along their thickness. Early friction stir processing conditions were used to obtain the graded microstructures with decreasing percentages of yttrium oxide (Y_2O_3) from the surface to the interior of the plate. Initially, particles of Y_2O_3 with diameter in the micrometer range are compacted within V-grooves machined on the copper plate surface. The powder particles are then incorporated into the plate by insertion of a rotating tool generating extrusion and forging. Contrary to usual processes (powder metallurgy, ion implantation, surface oxidation or nitriding), friction stir processing takes advantage of the possibility to treat variable depths of material in a few minutes. The sample microstructure and its gradual features are investigated at various scales by optical microscopy for the grain structure and by scanning electron microscopy for the powder distribution. Furthermore, the microhardness profiles are measured at various depths across the graded material. The present paper deals with the correlation between the microstructure of an early sample and its mechanical properties.
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