Plastic Deformation

· FCC metals have more possible slip systems. These have different orientations with respect to the tensile axis of the deforming sample.

From: Hayden, Moffatt & Wulff, "The Structure & Properties of Materials," Wiley (1965)

· The slip systems for the fcc lattice are shown above. The active slip systems will be those for which the resolved shear stress is equal to or larger than the critical shear stress. τ_res = σ cosθ cosΦ = τ_cr
· One system will become active at the start of deformation. As that system work hardens, the resolved stress on other systems will increase and they can become active once the critical shear stress, τ_cr , is exceeded.