Evolution of microstructure and mechanical properties in Cu–14%Fe alloy during severe cold rolling

Abstract

Cu–14%Fe alloy was produced by vacuum arc remelting and casting in water-cooled mold with subsequent hot extrusion. It had fine grained microstructure with supersaturated solid solutions based on Cu and Fe phases. The alloy was subjected to cold sheet rolling with true strains up to 6.6. Microstructure was studied by SEM and TEM, specific attention was paid to chemical composition of individual phases—copper matrix and iron particles. After rolling very fine lamellar structure formed in copper matrix. Rolling also has resulted in decrease of iron content in matrix from 3.8% in initial condition to 1% after rolling with strain of 5.1 due to decomposition of supersaturated solid solution. At higher strain some deformation-induced mechanical alloying was observed, leading to local increase of iron content. Iron particles also were heavily refined; their average thickness after rolling with strain of 6.6 is about 30nm (according to TEM data). Several possible mechanisms of their refinement in addition to homogeneous plastic deformation are proposed. Strength of the alloy measured by tensile testing increased significantly after rolling. For example, ultimate tensile strength increased from 325MPa in initial condition to almost 1000MPa after rolling with strain of 6.6. Good correlation between mechanical strength and spacing between iron particles in accordance with Hall–Petch relationship was found.