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Procedures for Strengthening Crystals

IP.com Disclosure Number: IPCOM000077960D
Original Publication Date: 1972-Oct-01
Included in the Prior Art Database: 2005-Feb-25
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Matthews, JW: AUTHOR

Abstract

Overcoatings of controlled type and composition can provide strength greater than the sum of the inherent strengths of the coating and the base material. Surface film which inhibits the formation and escape of dislocations greatly increases the strength of the substrate crystal. These procedures are particularly useful for strengthening thin films.

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Procedures for Strengthening Crystals

Overcoatings of controlled type and composition can provide strength greater than the sum of the inherent strengths of the coating and the base material. Surface film which inhibits the formation and escape of dislocations greatly increases the strength of the substrate crystal. These procedures are particularly useful for strengthening thin films.

For one procedure, a surface film which is particularly effective for impeding the introduction or escape of dislocation on a crystal surface is one which grows coherently, i.e., with perfect lattice match on the substrate but which has a different crystal structure. Illustratively this phenomenon occurs in iron deposited on the (001) surface of gold. The strengthening effect of films of this type arises from the fact that dislocations which are able to move through one of the crystals, find it difficult to move through the other. The difficulty exists because passage of a dislocation from one crystal to the other involves a change in Burger's vector and slip plane.

For another procedure, if cobalt is deposited onto clean (001) nickel surfaces, the initial deposit is face-centered-cubic and elastically strained to match the substrate lattice. When the deposit thickness reaches a critical value, misfit dislocations are made. These dislocations are unusual because they are imperfect and "supersessile," which means that they cannot move by climb or by glide. When the cobalt layer is s...