Compressive properties of Al-A206/SiC and Mg-AZ91/SiC syntactic foams
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Nikhil Gupta Mechanical and Aerospace Engineering Department, Polytechnic Institute of New York University, Brooklyn, New York 11201
Pradeep Kumar Rohatgi Materials Science and Engineering Department, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin 53201 (Received 1 February 2013; accepted 5 June 2013)
Metal matrix syntactic foams are promising materials with high energy absorption capability. To study the effects of matrix strength on the quasistatic compressive properties of syntactic foams using SiC hollow particles as reinforcement, matrices of Al-A206 and Mg-AZ91 were used. Because Al-A206 is a heat-treatable alloy, matrix strength can be varied by heat treatment conditions, and foams in as-cast, T4, and T7 conditions were tested in this study. It is shown that the peak strength, plateau strength, and toughness of the foams increase with increasing yield strength of the matrix and that these foams show better performance than other foams on a specific property basis. High strain rate testing of the Mg-AZ91/SiC syntactic foams showed that there was little strain rate dependence of the peak stress under strain rates ranging from 103/s to 726/s.
I. INTRODUCTION
Metal matrix syntactic foams (MMSFs) are a class of cellular metals that usually contain over 30 vol% of hollow spheres and offer superior blast and energy absorption capabilities due to their distinctive compressive deformation behavior. Similar to other cellular metals,1–3 the compressive deformation of MMSFs involves strain to an initial peak stress, followed by a stress plateau that is sustained to a large strain until the foam is fully densified. This behavior is ideal for the absorption of energy at a low stress and has led to numerous studies designed at tailoring the properties of MMSFs through matrix alloy selection, hollow particle reinforcement selection (including composition, diameter, wall thickness, and uniformity), and material process optimization.4–30 A majority of the studies on MMSFs have focused on elucidating the roles various combinations of matrix and reinforcement have on the mechanical properties. Various alloys of aluminum,4–20,26,27 magnesium,20–23 zinc,20,24 titanium,10,25 and iron10,26–30 have been reinforced with hollow spheres of mullite,4,5 fly ash,6–16,23–25 glass,20,30 Al2O3,17,18,21,29 steel,26–28 carbon,22 and SiC.19 Due to the a)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2013.176 2426
J. Mater. Res., Vol. 28, No. 17, Sep 14, 2013
http://journals.cambridge.org
Downloaded: 14 Mar 2015
large number of combinations that have been used, drawing comparisons can be difficult. A useful method of comparing the mechanical properties of syntactic foams regardless of composition is by the reinforcement wall thickness (t) to diameter (D) ratio. It has been shown in a variety of Al- and Mg-based MMSF systems that the peak strength of these MMSFs increases with increasing t/D ratio.6,17,21 A closer examination of the properties of A201-O and A201-T6-alumina17 syntactic foams and th
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