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Steel and Titanium Hollow Sphere Foams

Published online by Cambridge University Press:  10 February 2011

K. M. Hurysz ,
J. L. Clark ,
A. R. Nagel ,
C. U. Hardwicke ,
K. J. Lee ,
J. K. Cochran  and
T. H. Sanders Jr
K. M. Hurysz
Affiliation:
Georgia Institute of Technology, Materials Science and Engineering, Atlanta, GA 30332-0245
J. L. Clark
Affiliation:
Georgia Institute of Technology, Materials Science and Engineering, Atlanta, GA 30332-0245
A. R. Nagel
Affiliation:
Georgia Institute of Technology, Materials Science and Engineering, Atlanta, GA 30332-0245
C. U. Hardwicke
Affiliation:
Physical Metallurgy Laboratory, General Electric Corporation, Schenectady, NY 12301
K. J. Lee
Affiliation:
Georgia Institute of Technology, Materials Science and Engineering, Atlanta, GA 30332-0245
J. K. Cochran
Affiliation:
Georgia Institute of Technology, Materials Science and Engineering, Atlanta, GA 30332-0245
T. H. Sanders Jr
Affiliation:
Georgia Institute of Technology, Materials Science and Engineering, Atlanta, GA 30332-0245
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Abstract

Metal hollow sphere foams are fabricated by bonding millimeter sized metal alloy hollow spheres at points of contact. The spheres are formed as powder shells from slurries. For stainless steel spheres, the starting powder is a mixture of iron and chromium oxide. Thermal treatment in hydrogen reduces the oxides to Fe/Cr alloys with less than 2% porosity in sphere walls. The nominal composition is close to that of 405 stainless. Carburization in CO/CO2 atmosphere followed by heat treatment produces foams of either 410 or 420 type stainless steels depending on carbon content. Compressive stress-strain behavior was measured on point contact bonded stainless foams both before and after carburization. Hardness measurements on steel sphere walls were used to estimate the yield strength. Relative strengths of the foams were positioned between open and closed cell models. This was encouraging because bonding in the foams was less than optimum and the hollow sphere walls contained defects. As processing improves, strengths should increase. To produce titanium alloy spheres, the starting powder is titanium alloy hydride. Thermal treatment in an inert atmosphere decomposes the hydride and sinters the titanium powder in the sphere walls to greater than 96% relative density. Both titanium and Ti-6V-4V spheres and foams have been produced. Oxygen contents are a concern for titanium compositions and processing is being altered to reduce oxygen levels to increase ductility

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 521: Symposium R – Porous & Cellular Materials for Structural Applications , 1998 , 191
Copyright
Copyright © Materials Research Society 1998

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References

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