Plastic deformation behaviour of Fe-Cu composites

Abstract

Two-phase composites, which consist of spherical polycrystalline α-iron and copper particles, are studied mechanically under large plastic deformation. Such polycrystals are produced from mixtures of iron and copper powders by powder metallurgy. Due to the significant difference of the yield stress in the iron and the copper phase in which the slip system geometry is also dissimilar, a high heterogeneity and anisotropy characterize the plastic deformation behaviour. In such bcc-fcc polycrystals, the harder phase shows higher stresses while the softer phase undergoes a larger deformation. To successfully predict the mechanisms of the plastic deformation for a certain grain, effects of the major factors should be taken into account like, e.g., the microscopic interaction, the influence of neighbouring grains, the phase volume fraction, the morphology, and the initial crystallographic texture. In this work, an elasto-viscoplastic material model is applied in axisymmetric finite element simulations, whereas the macroscopic material behaviour is established based on constitutive equations of the single crystal. In the simulations, real two-dimensional microstructures are selected as cross-sections in the axisymmetric model. The material parameters are identified from the experimental data in compression tests. Numerical predictions include the flow behaviour, the crystallographic texture, and the local strain in Fe-Cu composites. In particular, a quantitative study is performed for the mean value of the local strain in both phases, which shows a good agreement with the experimental result for the Fe17-Cu83 composite under tension. Numerical predictions and experimental measurements are compared for the flow behaviour and the texture in both Fe17-Cu83 and Fe50-Cu50 composites. © Springer Berlin Heidelberg 2008.