Slip is defined as a shear deformation that moves atom by many inter-atomic distances in one crystal plane over the atoms of another crystal plan. Because of the plastic deformation , the crystal divided into layers or slip blocks are separated by thin layers in which a considerable displacement of atoms has taken place.
GRAIN STRUCTURE - GRAIN STRUCTURE refers to the arrangement of grains in metal , with a grain have a particular crystal structure.
The mechanical properties of metals that obtain maximum strength depend upon the arrangement of the grains , their shape and especially their size. Grain Size directly controls the extent of slip interference by adjacent grains and strength ,toughness,ductility and fatigue of metal are thus affected.The fine grain structure has a small grain size wheres coarse grain structure has a large grain size.The grain size is controlled by several factors out of which temperature and time of heating are important.
A very important feature of a metal is average size of grain. The size of grain determines the property of the metals. for example smaller grain size increases the tensile strength and tends to increase ductility. A larger grain size is preferred for improved high temperature creep property. CREEP is a permanent deformation that increases with time under constant load or stress.
Another important property of grain is their orientation. The random arrangements grain such that n one direction within the grain is aligned with external boundaries of the metal sample.The random orientation can be obtained by cross rolling the material.if such a sample were rolled sufficiently in one direction,it might develop a grain oriented structure in the rolling direction.This is called preferred orientation.In some cases preferred orientation is very desirable but in some instances it may be harmful
The grain boundaries refers to the outside area of a grain that separates it from the other grain.The grain boundaries separate variously oriented crystal regions in which the crystal structure are identical.
A grain boundary is a interface between two different orientation of grain structure in material . Grain boundaries are defects in the crystal structure, and tend to decrease the electrical and thermal conductivity of the material.