Steel and titanium hollow sphere foams
- Georgia Inst. of Tech., Atlanta, GA (United States)
- General Electric Corp., Schenectady, NY (United States). Physical Metallurgy Lab.
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/CO{sub 2} 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.
- Sponsoring Organization:
- Defense Advanced Research Projects Agency, Arlington, VA (United States); Office of Naval Research, Washington, DC (United States)
- OSTI ID:
- 361820
- Report Number(s):
- CONF-980405-; TRN: IM9933%%202
- Resource Relation:
- Conference: Spring meeting of the Materials Research Society, San Francisco, CA (United States), 13-17 Apr 1998; Other Information: PBD: 1998; Related Information: Is Part Of Porous and cellular materials for structural applications; Schwartz, D.S.; Shih, D.S. [eds.] [Boeing Co., St. Louis, MO (United States)]; Evans, A.G. [ed.] [Harvard Univ., Cambridge, MA (United States)]; Wadley, H.N.G. [ed.] [Univ. of Virginia, Charlottesville, VA (United States)]; PB: 337 p.; Materials Research Society symposium proceedings, Volume 521
- Country of Publication:
- United States
- Language:
- English
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