Effect of Microstructural Anisotropy of PM Precursors on the Characteristic Expansion of Aluminum Foams
This work investigates the causes of the anisotropic early expansion (below the melting point) of powder metallurgical (PM) aluminum foam precursors by evaluating the crystallographic anisotropy induced during the production of the precursor materials. A varied group of precursors prepared using different parameters and techniques (direct powder extrusion and hot uniaxial compression) has been investigated. Multidirectional foaming expansion has been registered in situ by means of the optical expandometry technique, while X-ray diffraction has been used to characterize the preferred crystallographic orientation (texture) of the pressed powders. The results point to a clear correlation between the expansion anisotropy and the microstructural crystallographic anisotropy of the precursors. Although this correlation is not a direct cause–effect phenomenon, it is a good indicator of intrinsic precursor characteristics, such as densification and powder interparticle bonding, which govern the expansion behavior during the early stages when the material is still in a solid or semisolid state.
KeywordsFoam Aluminum Foam Compaction Pressure Expansion Behavior Semisolid State
Financial assistance from the MCINN and Feder Program (MAT2009-14001-C02-01 and MAT 2012-34901), the Junta of Castille and Leon (VA174A12-2) and the European Space Agency (Project MAP AO-99-075) is gratefully acknowledged. In addition, the authors are grateful to the Spanish Ministry of Economy and Competitiveness, which supported this investigation with a FPU-doctoral grant Ref-AP-2007-03318 (J. Lázaro) and a Juan de la Cierva contract of E. Solórzano (JCI-2011-09775). Financial support for PIRTU contract of E. Laguna-Gutierrez by Junta of Castile and Leon (EDU/289/2011) and co-funded by the European Social Fund is also acknowledged. The authors would also like to thank the Alulight Company for providing some of the precursor materials used in this study.
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