Date of Award

Summer 1967

Degree Type

Thesis - Restricted

Degree Name

Master of Science (MS)

Department

Mechanical Engineering

First Advisor

Hirthe, Walter M.

Second Advisor

Blumenthal, Robert N.

Third Advisor

Jansen, Richard J.

Abstract

Many investigations have been conducted to more fully develop the family of high strength Maraging Steels first introduced about 1960. Because of the sensitivity of internal friction to structural changes within materials, even on the atomic level, this test method was used to help explain some of the effects of thermo-mechanical treatments on the behavior of Maraging Steel. Hardness, tensile, and impact tests were also performed, and compared with existing data. A study of the microstructure and topography of fracture surfaces was also conducted. The material used in this investigation was a 1/4" thick hot rolled sheet of the 250 grade Maraging Steel. The material was initially double solution treated at 1650°F and 1510°F. Three different percent cold reductions and six different aging treatments were investigated. It is shown that the dynamic modulus of elasticity decreases with temperature, especially when averaging starts. An internal friction peak was found to exist below room temperature in the vicinity of -50°F. Also, based on internal friction data it was discovered that the maximum service temperature for this material should be below 700°F. And finally, it was found that a ductile to brittle transition temperature range probably exists below -25°F. However, for Maraging Steel the drop in impact energy absorbed during fracture is not as sudden or as much as it is for many carbon steels at the ductile to brittle transition temperature.

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