Which is weaker has the lower yield strength a crystal with

Which is weaker (has the lower yield strength) a crystal with a dislocation or a crystal of the same material without a dislocation? CIRCLE THE BEST ANSWER With a dislocation. Without a dislocation. c) The will have the same strength. It is impossible to say. Briefly explain:

Solution

Ans. option (a)

because

In materials science, a dislocation is a crystallographic defect, or irregularity, within a crystal structure. The presence of dislocations strongly influences many of the properties of materials. The theory describing the elastic fields of the defects was originally developed by Vito Volterra  but the term \'dislocation\' to refer to a defect on the atomic scale was coined by G. I. Taylor . Some types of dislocations can be visualized as being caused by the termination of a plane of atoms in the middle of a crystal. In such a case, the surrounding planes are not straight, but instead they bend around the edge of the terminating plane so that the crystal structure is perfectly ordered on either side. The analogy with a stack of paper is apt: if half a piece of paper is inserted in a stack of paper, the defect in the stack is only noticeable at the edge of the half sheet.

There are two primary types: edge dislocations and screw dislocations. Mixed dislocations are intermediate between these.