Question

by what mechanism plastic deformation takes in metals

Answer 1

Two prominent mechanisms of plastic deformation, namely slip and twinning . • 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.During slip each atom usually moves same integral number of atomic distances along the slip plane producing a step, but the orientation of the crystal remains the same. • Generally slip plane is the plane of greatest atomic density, and the slip direction is the close packed direction within the slip plane. Twining : • Portion of crystal takes up an orientation that is related to the orientation of the rest of the untwined lattice in a definite, symmetrical way.The twinned portion of the crystal is a mirror image of the parent crystal. • The plane of symmetry is called twinning plane. • The important role of twinning in plastic deformation is that it causes changes in plane orientation so that further slip can occur.