Accession Number : AD0649168

Title :   A STUDY OF THE EARLY STAGES OF PLASTIC DEFORMATION.

Descriptive Note : Final rept.,

Corporate Author : PENNSYLVANIA UNIV PHILADELPHIA SCHOOL OF METALLURGICAL ENGINEERING

Personal Author(s) : Brown,Norman

Report Date : 17 MAR 1967

Pagination or Media Count : 16

Abstract : This is a review of research on microplasticity from 1956 to 1965. Topics related to microplasticity were: (1) the effect of grain size (2) low temperature deformation of body centered cubic metals (3) deformation of single crystal and polycrystalline face centered cubic metals (4) strength of martensite, (5) sodium chloride and (6) dispersion strengthening. In general, the transition from elastic to plastic behavior was characterized by an elastic limit, a microplastic limit and an energy loss in the anelastic region. Important conclusions from the research were: (1) The amount of pre-yield microstrain varies as strongly as the cube of the grain size in some metals and is independent of grain size in others. (2) The elastic limit of body centered cubic metals has a very small dependence on temperature even down to 5 degrees K when compared to the microscopic yield point. (3) A small amount of plastic strain reduces the elastic limit of an annealed crystal. (4) In a dispersion strengthened system, the elastic limit is independent of the dispersion once the material is strained elastically. (5) The structure involving dispersed particles which are connected by grown in dislocations gives a strengthening which varies inversely as the square root of the spacing between particles. (6) The microplastic limit of as-quenched iron-carbon martensite at a plastic strain resistivity of about (10-6) is about one-half of the microscopic yield point.9 (7) After tempering iron-carbon martensite to about 280 degrees the microplastic limit and the microscopic yield points are about the same.

Descriptors :   (*METALS, DEFORMATION), (*DEFORMATION, PLASTIC PROPERTIES), GRAIN SIZE, SINGLE CRYSTALS, MARTENSITE, ELASTIC PROPERTIES, CRYSTAL DEFECTS, YIELD POINT, PHASE STUDIES, STRAIN(MECHANICS)

Subject Categories : Properties of Metals and Alloys
      Crystallography
      Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE