Theory of Plastic Deformation Mechanism for Face-centered Cubic Metals

Abstract

The activation of plastic deformation mechanisms determines the mechanical behavior of crystalline materials. For face-centered cubic metals, the stacking fault has been widely used to interpret the intragranular deformation mechanisms, twinning, stacking fault, and full slip. However, the current description of plastic deformation with stacking fault energy is still empirical and weak on the physical basis. The generalized planar fault energy was proposed as an alternative parameter but still the interpretation contains unresolved problem which is not clearly understood. Here, we put forward a transparent theory of plasticity based on the generalized planar fault energy. We demonstrate that grain orientation can drastically alter the deformation mode activity and propose the concept of effective energy barrier to reflect the orientation effect. Finally, a single parameter derived from the intrinsic energy barriers is identified. Based entirely on this parameter, a simple deformation mode diagram is shown to delineate a series of convenient criteria of metals. Additionally, the effect of stress types on deformation mechanism fraction is revealed.