Bulk mechanical alloying of Cu–Ag and Cu/Zr two-phase microstructures by accumulative roll-bonding process

Abstract

Cu–Ag eutectic alloy and multilayered stacked sheets of Cu/Zr were repeatedly cold-rolled by the accumulative roll-bonding (ARB) process as attempts of bulk mechanical alloying. Both ARB-processed two-phase microstructures were deformed into a very fine lamellar structure with a spacing of several nm. The Cu–Ag sheets were deformed by a number of multiple shear bands after two cycles of ARB. Intermixing of Cu and Ag occurred within the fine Cu lamellae and the shear bands. On the other hand, the Cu/Zr sheets were deformed inhomogeneously accompanied by the formation of multiple fracturing and necking of the coarse Zr layers. The Zr layers were fragmented into fine nodules after five or six cycles. The ARB processed specimen with an equivalent strain of 14.1 showed that amorphization starts from the Cu/Zr interfaces. The microstructural changes are discussed from the Gibbs free energy diagrams.