![]() Imagine cutting a crystal along a plane and slipping one half across the other by a lattice vector, the halves fitting back together without leaving a defect. A screw dislocation is much harder to visualize. If a screw dislocation is followed all the way around a complete circuit, it would show a slip pattern similar to that of a screw thread. Screw dislocations can be produced by a tearing of the crystal parallel to the slip direction. DOE Fundamentals Handbook, Volume 1 and 2. The term ‘dislocation’ referring to a defect on the atomic scale was coined by G. During the 1930s it was theorized that this discrepancy in mechanical strengths could be explained by a type of linear crystalline defect that has come to be known as a dislocation. But these theoretical strengths were many times greater than those actually measured. ![]() They must end at a crystal edge or other dislocation, or they must close back on themselves.Įarly materials studies led to the computation of the theoretical strengths of perfect crystals. It is important to note that dislocations cannot end inside a crystal. Mixed dislocations, combining aspects of both types, are also common. There are two basic types of dislocations, the edge dislocation and the screw dislocation. ![]() Dislocations are especially important in materials science, because they help determine the mechanical strength of materials. Line defects are called dislocations and occur in crystalline materials only. Line defects are generally many atoms in length. ![]()
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