Date of Award

Fall 1974

Document Type

Thesis - Restricted

Degree Name

Master of Science (MS)

Department

Mechanical Engineering

First Advisor

Fournell, Raymond

Second Advisor

Hirthe, Walter M.

Third Advisor

Blumethal, Robert

Abstract

The yield strength of annealed low alloy steels is a function of several microstructural variables such as grain size and second phase particle dispersions as well as solutes in solid solution and substructure effects, dislocation density, and twinning. The purpose of this research is to quantitatively determine the contribution of each factor to the yield strength and express these contributions in equation form. The alloys under investigation are a ferritic and martensitic, copper precipitation hardening steels heat treated to the peak age condition for several varying microstructures of each alloy. Measurements of grain size, martensitic lath width and carbide spacing are obtained through light and electron microscopic techniques while the remaining contributions to the yield strength are taken from data supplied in the literature. It was found that the yield strength of the ferritic steel is proportional to the reciprocal square root of the grain size and can be expressed by an equation of the form: "formula"...

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