Slip is the prominent mechanism of plastic deformation in metals . It involves sliding of blocks of crystal over one other along definite crystallographic planes, called slip planes. • it is analogous to a deck of cards when it is pushed from one end. Slip occurs when shear stress applied exceeds a critical value.
What is slipping and twinning?
During slip, all atoms in a block move the same distance . During twinning , the atoms in each successive plane in a block move through different distances proportional to their distance from twinning plane. Slip is commonly observed in Body-centered Cubic (BCC) and Face Centered Cubic (FCC) metals.
What is slip dislocation?
Slip occurs by the passage of dislocations on close packed planes which are planes containing the greatest number of atoms per area and in close-packed directions (most atoms per length). Close-packed planes are known as slip or glide planes. ... The magnitude and direction of slip are represented by the Burgers vector.
How does deformation occur by slip?
Plastic deformation may occur by slip, twinning, or a combination of slip and twinning. Slip occurs when a crystal is stressed in tension beyond its elastic limit . It elongates slightly, and a step appears on the surface, indicating displacement of one part of the crystal.
What is slip direction?
The slip direction is the direction in which the dislocation moves , which is the direction of the Burgers vector for edge dislocations. During slip, the edge dislocation sweeps out the plane formed by the Burgers vector and the dislocation; this plane is called the slip plane.
What does slip mean in engineering?
Slip, in engineering and physics, sliding displacement along a plane of one part of a crystal relative to the rest of the crystal under the action of shearing forces—that is, forces acting parallel to that plane.
Do all metals have the same slip system?
(b) All metals do not have the same slip system . The reason for this is that for most metals, the slip system will consist of the most densely packed crystallographic plane, and within that plane the most closely packed direction. This plane and direction will vary from crystal structure to crystal structure.
Is twinning a slip mechanism?
Twinning and slip are competitive mechanisms for crystal deformation . Each mechanism is dominant in certain crystal systems and under certain conditions. In fcc metals, slip is almost always dominant because the stress required is far less than twinning stress.
What are the types of twinning?
There are two types of twins – identical (monozygotic) and fraternal (dizygotic) . To form identical twins, one fertilised egg (ovum) splits and develops two babies with exactly the same genetic information.
What causes twinning?
Dizygotic or fraternal twins form in the same way that all humans do, by the union of sperm and egg . The explanation for dizygotic twinning lies in the cause of hyperovulation, which is the release of more than one egg in a cycle of ovulation.
How many slip systems are in HCP?
Hence, the h.c.p. structure exhibits three distinct slip systems . The h.c.p structure has only two independent slip systems, since any slip on [110](001) can be described entirely as a combination of slip on [100](001) and [010](001). Hexagonal close packed crystals slip on <100>{001} slip systems.
Is plastic deformation permanent?
Plastic deformation is the permanent distortion that occurs when a material is subjected to tensile, compressive, bending, or torsion stresses that exceed its yield strength and cause it to elongate, compress, buckle, bend, or twist.
What are the slip systems in FCC?
FCC slip occurs on close-packed planes in close-packed directions . There are 4 octahedral planes, (111), (111), (111), and (111), six <110> directions, each one common to two octahedral planes, giving 12 slip systems. Figure 7.2. The (111) plane in the FCC system is shown shaded.
What is an independent slip system?
by an independent slip system, i.e., a slip system is. independent if the pure (.distortional) strain pro- duced by its operation cannot be produced by a suit- able combination of glide on other systems (von.
What is primary slip plane?
We can calculate the resolved shear stress acting parallel to the slip direction on the slip plane as follows. The area of the slip plane is A/cosφ, where φ is the angle between the tensile axis and the slip plane normal. ... The crystal begins to plastically deform by slip on this system, known as the primary slip system.
