New Composite Metal Foams under Compressive Cyclic Loadings

Abstract

New composite metal foams are processed using powder metallurgy (PM) and gravity casting techniques. The foam is comprised of steel hollow spheres, with the interstitial spaces occupied by a solid metal matrix (Al or steel alloys). The cyclic compression loading of the products of both techniques has shown that the composite metal foams have high cyclic stability at very high maximum stress levels up to 68 MPa. Under cyclic loading, unlike other metal foams, the composite metal foams do not experience rapid strain accumulation within collapse bands and instead, a uniform distribution of deformation happen through the entire sample until the densification strain is reached. This is a result of more uniform cell structure in composite metal foams compared to other metal foams. As a result, the features controlling the fatigue life of the composite metal foams have been considered as sphere wall thickness and diameter, sphere and matrix materials, and processing techniques as well as bonding strength between the spheres and matrix.

Ballistic performance of composite metal foams

“…This material has shown superior mechanical properties compared to any other metal foam [7][8][9][10][11][12][13][14][15]. These outstanding qualities of CMFs are further improved under high-speed impact type of loading (similar to that in ballistic impact) compared to quasi-static loading [16].…”

“…Steel-steel Composite Metal Foam (S-S CMF) panels were manufactured using hollow spheres embedded in a stainless steel powder matrix and processed using powder metallurgy technique previously developed [8,10,12,16,18]. Hollow steel spheres with 2 mm outer diameter and 200 µm sphere wall thickness were manufactured by Hollomet GmbH in Dresden, Germany using lost core technique [19,20].…”

Effect of Sphere Properties on Microstructure and Mechanical Performance of Cast Composite Metal Foams

“…Aluminum matrix CMF with steel hollow spheres has been studied extensively under monotonic compression and fatigue loading [1][2][3][4][5][6][7][8] and has shown mechanical properties unmatched with any other metal foam. As previously reported [3,4,7,8] aluminum-steel (Al-S) CMF contains hard and brittle intermetallic from the Al-Fe-Si ternary system dispersed through the matrix of the material.…”

“…The formation of intermetallics in the Al-Fe-Si system is a well-studied phenomena [9][10][11][12][13][14][15] and is due to the reciprocal diffusion of Fe and other alloying elements, like Cr and Ni, from the sphere wall into the Al-Si matrix, at the same time of diffusion of Al and Si from the matrix towards the sphere wall. Intermetallic formation in Al-S CMF influences the mechanical properties of the material and for that reason it has been widely studied [1][2][3][4][5][6][7][8]. In this study, the microstructure of Al-S CMF manufactured using spheres with different properties is investigated using SEM images along with EDS analysis.…”

“…The furnace used for heating up the spheres, mold and aluminum is a high temperature furnace from CM furnaces 3300 series (Bloomfield, NJ, USA) with molydisilicide heating elements capable of reaching 1700 °C. More details on the processing of composite metal foam via casting are presented elsewhere [1][2][3][4][5][6][7][8].…”