Date of Award

Spring 1969

Degree Type

Thesis - Restricted

Degree Name

Master of Science (MS)

Department

Mechanical Engineering

First Advisor

Jansen, Richard J.

Second Advisor

Hirthe, Walter M.

Third Advisor

Blumenthal, Robert N.

Abstract

The aging and overaging characteristics of 18% Ni (300) maraging steel are studied for aging times of up to twenty weeks at temperatures in the 700°F-1300°F range. The volume fraction of the amount of reverted austenite in overaged samples is determined by both density and magnetic techniques. The effect of austenite content on mechanical properties is observed; specifically, hardness and micro-hardness, impact toughness at the exposure temperature and at room temperature, yield strength and ultimate tensile strength data are determined as a function of heat treatment. The proposed homogenization of samples found to have reached a maximum degree of austenite reversion is investigated by a reaging treatment designed to detect the presence of annealed martensite in the overaged steel. Metallographic examination is conducted with both optical and electron microscopy as a supplementary study. The microstructure of severely banded specimens and other selected samples is discussed.

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