Evaluation of mechanical properties of porous 6061 alloys fabricated by the powder compression and induction heating pro
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9/27/04
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Evaluation of Mechanical Properties of Porous 6061 Alloys Fabricated by the Powder Compression and Induction Heating Process S.W. YOUN and C.G. KANG The purpose of this study is to evaluate the mechanical properties of 6061 Al foam products, which were fabricated by the powder compression and multistep induction heating method, and to build the database necessary for computer-aided modeling or foam components design. In this study, 6061 Al foams with various porosity fractions were fabricated according to the porosity fractions–final heating temperature curve. The relationships between porosity fraction and morphological properties (porosity diameter, number per unit area of porosities, and surface skin thickness) were investigated. Mechanical properties such as compressive strength, energy absorption capacity, and efficiency were investigated to evaluate the feasibility of foams as crash-energy-absorbing components. Furthermore, the effect of the surface skin thickness on the plateau stress and strain sensitivity of the 6061 Al foam with low porosities (pct) was studied.
I. INTRODUCTION
ALUMINUM foam is an ultra-lightweight porous material consisting of aluminum and large quantities of porosities. It has high stiffness at very low density, high impact energy absorption, heat and fire resistance, and greater thermal stability than any organic material.[1,2] One of the advantages of foam material is that the material with required mechanical properties can be produced by controlling the porosities. In spite of the advantages mentioned previously, Al foam is hardly used in the industry. One reason is the difficulty of reproducing mechanical properties. In order to use foamed metal as a tailored material in the industry, the following points need to be investigated. One is the relationship between morphological and mechanical properties; another is the fabrication condition for Al foam, which satisfies the desired morphological properties. In addition, for the purpose of a finite- element analysis, the establishment of a data base of mechanical properties is essential. One of the most important application fields for Al foam in general is energy absorption, because of Al foam’s low rebound in dynamic crash situations and much higher strength than polymer foam. Generally, foamed metal has a porosity fraction that ranges approximately from 70 to 90 pct, because the greater a metal’s porosity, the greater its usable strain as an energy absorber.[3] Therefore, so far, studies on the mechanical properties of foamed metal have been conducted mainly on metals with porosity fractions greater than 70 pct. Wan and colleagues have researched the deformation behavior of foamed material and the energy absorption rate in accordance with the variation of porosity fraction through a compression experiment on AlSi7Mg0.45 alloys with porosity fractions of 75 to 85 pct.[4] Yu et al. have reported that compressive strength of A6061 alloys with porosities of 70 to 90 pct is dominated by relative density and
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