Material science Research Paper Example | Topics and Well Written Essays - 500 words

Material science - Research Paper Example GBS has also been found to be a major means of deformation for polycrystalline materials leading to the belief that GBS controls superplasticity properties. GBS refers to the displacement occurring when two grains subjected to external stress slide over one another in which the movement occurs at or in closer proximity to the common interface between the grains (Langdon 598). The occurrence of grain boundary sliding has been demonstrated by several scholars over the years. Grain boundary sliding has increasingly become an area of interest among material scientists. Two different forms of GBS have been suggested. The first form of GBS suggested by Rachinger in 1952 involves the displacement of nearby grains in which the grain’s original shape and size is retained despite being evidently displaced over each other (Mayo and Nix 2). This phenomenon has been demonstrated as a form of deformation in polycrystalline materials under creep situations where the number of grains within the measured length increases in the same direction as the external tensile stress (Rachinger 81). Rachinger GBS exists under two different situations namely; conventional creep where the size of the grain d exceeds that of the equilibrium sub-grain as well as in superplasticity where the grain size is smaller than the equilibrium size of the sub-grain (Langdon 598). Both GBS GBS also exists in form of Lifschitz sliding which represents the offsets in the boundaries that occur due to stress and does not increase the number of measured grains (Langdon 598). The main difference between the two GBS forms is that while Lifschitz is an accommodation process by itself, Rachinger sliding entails accommodation through intragranular grip (Nieh, Sherby and Wadsworth 40). The two GBS types have been unified through rate equations which are consistent with empirical observations (Vastava and Langdon 2339). Grain boundary sliding also plays a significant role in superplasticity.