Leland Stanford Junior University

USA As Represented by Secretary of the Navy

University of California

Sptek

Oleg D Sherby

Toshimasa Oyama

Jeffrey Wadsworth

Richard L Landingham

Michael J Strum

Conrad M Young

Bruno Walser

Irvin C Huseby

Eldon M Cady, Jr

Robert Whalen

Oscar Ruano

Dong W Kum

Alfred Goldberg

Steven L Robinson

Ultrahigh carbon steels with superplastic properties are produced by heating a steel containing ferrite and carbide phases to a soaking temperature approximately 50.degree. C. above the A.sub.1 transformation temperature, soaking the steel above the A.sub.1 temperature for a sufficient time that the major portion of the carbides dissolve into the austenite matrix, and then cooling the steel in a controlled manner within predetermined limits of cooling rate or transformation temperature, to obtain a steel having substantially spheroidal carbides. New alloy compositions contain aluminum and solute additions which promote the formation of a fine grain size and improve the resistance of the carbides to coarsening at the forming temperature.

Transformation process for production of ultrahigh carbon steels and new

An ultrahigh carbon steel having a composition of carbon in an amount of from about 0.8 weight percent up to the maximum solubility limit of carbon in austenite, aluminum in an amount of from about 0.5 to about 10 weight percent, an effective amount of a stabilizing element acting to stabilize iron carbide against graphitization, and the balance iron. Preferably, the aluminum is present in an amount of from about 0.5 to about 6.4 weight percent and the stabilizing element is chromium. The steel has excellent ductility and is readily hot, warm and cold worked without cracking. It is particularly useful in superplastic forming operations, and may be processed to a suitable microstructure by any technique which reduces its grain size to about 10 microns or less, and preferably to about 1 micron. Such a very fine grain size is readily acheived with the steel, and the aluminum and stabilizing additions act to retain the fine grain size during superplastic processing.

Ultrahigh carbon steels containing aluminum

An ultra high carbon steel having a composition of carbon in an amount of from about 0.8 weight percent up to the maximum solubility limit of carbon in austenite; silicon in an amount of from about 3 to about 7 weight percent; an effective amount of a stabilizing element acting to stabilize iron carbide against graphitization in the presence of silicon; and the balance iron. Preferably, the silicon is present in an amount of about 3 weight percent, and the stabilizing element is chromium. The ultra high carbon steel may be processed to a form suitable for subsequent superplastic forming by any technique which reduces its grain size to about 10 microns or less, and preferably to about 0.4 to about 2 microns. The silicon and the stabilizing element act to produce a stable iron carbide particle array to retain the fine grain size during superplastic processing, and to increase the eutectoid temperature so that superplastic processing may proceed at high strain rates and low stress levels at elevated temperature.

Ultra high carbon steel alloy and processing thereof

A powder metallurgical method of consolidating iron-based alloy powder, particularly white cast iron, to form a body of high density in which the powder is thermally cycled above and below the alpha-gamma transformation temperature of below 800.degree. C., and a stress of between 1.7 MPa and 34.5 MPa is simultaneously applied to the powder to form a high density consolidated body.

Method for consolidation of iron-based alloy powder by cyclic phase

An ultrahigh carbon steel consisting of a structure formed by divorced eutectoid transformation with or without accompanying deformation such that substantially no pearlite is formed, having a fine grained iron matrix stabilized by cementite in spheroidized form. A method for processing the steel including heat treatment and mechanical working to form spheroidized proeutectoid carbide particles then reheating the steel for a time such that the carbon is not uniformly distributed in the austentite so that upon cooling, with or without accompanying deformation, a divorced eutectoid transformation occurs leading to a structure of spheroidized cementite in a fine ferrite grain matrix.

Divorced eutectoid transformation process and product of ultrahigh

A magnesium-boron composite is made by mechanically mixing magnesium powders with boron powders. An alternative embodiment includes mixing a small amount of lithium powder with the magnesium boron composite to improve the ductility. The mixed powders are processed by cold pressing, hot pressing, sintering, extruding, rolling and re-extruding.

Magnesium-boron particulate composites

An ultra high carbon steel with a fine grained iron matrix stabilized by cementite in predominantly spheroidized form at elevated temperatures. A method for treating the steel including heat treatment and mechanical working under sufficient deformation to refine the iron grain and spheroidize the cementite. Mechanical working is preferably performed either in the upper alpha-cementite range or in the gamma-cementite range. Thermal cycling may be substituted for mechanical working. An alternative method is mixing and sintering fine cementite containing-iron alloy powders and iron powders.

Growing community of inventors

Palo Alto, CA, United States of America

Oleg D Sherby