Development of high strength and high electrical conductive Cu and Cu–W composite by friction stir processing: Effect of traverse speed

Abstract

In this work, pure copper and copper-tungsten (Cu-W) surface composite is produced using a single pass friction stir processing (FSP) with an intention to enhance the hardness and wear resistance without impairing electrical conductivity. FSP is performed by changing the traverse speed from 50 to 200 mm/min and at a constant tool rotational speed of 600 rpm. The samples extracted from the stir zone are characterized for their microstructure, hardness, wear behaviour and electrical conductivity. The average grain size, at the stir zones, was significantly reduced (from 40 to 3 µm) after FSP. In the case of pure copper, the grain size decreased from 9 to 3 µm with an increase in traverse speed, however, grain size increased from 4 to 6 µm in the case of Cu-W composite. The hardness of FSP’ed Cu and FSP’ed Cu-W surface composite was increased in the order of 52% and 130% compared to the unprocessed copper. The wear rate significantly reduced after FSP also with an addition of W particles. A negligible reduction (1.83% IACS) in electrical conductivity was noticed for both Cu and Cu-W after FSP. This study demonstrates that the FSP is an effective approach to improve the surface mechanical properties of Cu without much impairing the electrical conductivity.