A STUDY OF THE EARLY STAGES OF PLASTIC DEFORMATION.
PENNSYLVANIA UNIV PHILADELPHIA SCHOOL OF METALLURGICAL ENGINEERING
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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.
- Properties of Metals and Alloys