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The two primary methods of deformation in metals are slip and twinning. Slip occurs by dislocation glide of either screw or edge dislocations within a slip plane. Slip is by far the most common mechanism. Twinning is less common but readily occurs under some circumstances. Twinning occurs when there are not enough slip systems to accommodate ...
Thus, a slip system in bcc requires heat to activate. Some bcc materials (e.g. α-Fe) can contain up to 48 slip systems. There are six slip planes of type {110}, each with two <111> directions (12 systems). There are 24 {123} and 12 {112} planes each with one <111> direction (36 systems, for a total of 48).
Deformation twinning is a response to shear stress. The crystal structure is displaced along successive planes of the crystal, a process also called glide. The twinning is always reflection twinning and the glide plane is also the mirror plane. Deformation twinning can be observed in a calcite cleavage fragment by applying gentle pressure with ...
Plasticity in a crystal of pure metal is primarily caused by two modes of deformation in the crystal lattice: slip and twinning. Slip is a shear deformation which moves the atoms through many interatomic distances relative to their initial positions.
Crystal plasticity assumes that any deformation that is applied to a material is accommodated by the process of slip, where dislocation motion occurs on a slip system. Further, Schmid's law is assumed to be a valid, where a given slip system is said to be active when the resolved shear stress along the slip system exceeds the critical resolved ...
These values vary with deformation temperature, strain rate and chemical composition. [ 3 ] [ 4 ] Researchers have shown that increased work hardening attributed to the partitioning of the austenite grains is the main contributing factor to the overall elongation of TWIP steels in which the mechanical strain of twinning have a rather small ...
Therefore, compressive stress in the direction perpendicular to the half plane promotes positive climb, while tensile stress promotes negative climb. This is one main difference between slip and climb, since slip is caused by only shear stress. One additional difference between dislocation slip and climb is the temperature dependence.
They found that T1 twinning was the dominant slip system at room temperature for strain rates between 10 −3 and 10 3 s −1. The basal slip did not contribute to deformation below 400°C. Twinning was found to be rate insensitive, and the rate sensitivity of slip could explain changes in twinning behaviour as a function of strain rate.