INTRODUCTION:
The concept of Cottrell atmosphere is important to many aspects of material sciences and engineering. This was first proposed by Cottrell and Bilby in 1949 to explain the interaction of solute carbon atoms with defects in steel. The Cottrell atmospheres occur under the interaction between the dislocations and impurities (alloying elements) in matrix metal. These defects, like a dislocation, produce long-range elastic stress fields that distort the interstitial lattice site around the defect in the matrix. These distorted lattice sites then provide lower energy sites for the solute carbon to occupy, thus relieving some of the stress field. This raises ...