Mechanical properties of A356 and ZA27 metallic syntactic foams at cryogenic temperature

Our manuscript has been accepted for publication in the Journal of Alloys and Compounds. The paper can be freely downloaded for the next 50 days.

Abstract This work presents compressions tests of metallic foams at cryogenic temperature. The investigated syntactic foams were manufactured by combining a packed bed of expanded glass particles with either an aluminium or a zinc matrix using infiltration casting. Uni-axial compressions tests were performed after submerging samples in a bath of liquid nitrogen with an equilibrium temperature of −196 °C. Both the solid matrix material and syntactic foam samples were tested. For comparison, room temperature reference data from the literature was obtained. In addition, the effect of thermal treatment on the mechanical behaviour of both alloys and their foams at cryogenic temperature was addressed. The results indicate significant embrittlement at cryogenic temperature; however, aluminium and its foams are less susceptible to this effect.

Influence of particle arrangement on the compression of functionally graded metal syntactic foams

Our paper has been accepted for publication in Materials Science & Engineering A and can be downloaded for free until 27.9.2019 using the following link.

Abstract This study probes the systematic spatial variation of two different types of filler particles in Metal Syntactic Foams (MSFs). The particle distribution is utilized to fabricate longitudinal and radial functionally graded metal syntactic foams. In addition, MSFs containing a random mixture of the same particles are tested. All samples are produced using a single step counter-gravity infiltration casting process. Quasi-static compression tests are performed to investigate the mechanical properties and deformation mechanisms of the resulting MSFs. The results indicate that MSF deformation is a combination of shear band and layer-by-layer modes. Moreover, functionally grading along the longitudinal direction yields the highest plateau stress and energy absorption.

Effect of Heat Treatment on the Compressive Behavior of Zinc Alloy ZA27 Syntactic Foam

Our manuscript “Effect of Heat Treatment on the Compressive Behavior of Zinc Alloy ZA27 Syntactic Foam” has been accepted for publication in Materials.

The paper is published in the special issue “Advanced and High Performance Metallic Foams” on the kind invitation of its editor Prof. Imre Orbulov.

Abstract: Zinc alloy (ZA27) syntactic foams (SF) were manufactured using expanded perlite (EP) particles and counter-gravity infiltration casting. Due to a variation of the metallic matrix content, the density of the produced foam samples varied from 1.78 to 2.03 gcm3. As-cast and solution heat-treated samples were tested to investigate the compressive properties of the ZA27 syntactic foam. To this end, quasi-static compression tests were conducted. In addition, microstructural analysis of the as-cast and heat-treated syntactic foams was carried out using scanning electron microscopy. The results indicate that the heat treatment alters the microstructure of the ZA27 alloy matrix from a multiphase dendrite to a spheroidized microstructure with improved ductility. Moreover, the heat treatment considerably enhances the energy absorption and plateau stress (spl) of the syntactic foam. Optical analysis of the syntactic foams under compression shows that the dominant deformation mechanism of the as-cast foams is brittle fracture. In comparison, the heat-treated samples undergo a more ductile deformation.

Functionally graded metal syntactic foam: Fabrication and mechanical properties

Our manuscript on functionally graded metal syntactic foam has been published in Materials & Design as an open access article.

Abstract: In this research study a novel functionally graded metal syntactic foam (FG-MSF) was manufactured using ex- panded perlite and activated carbon particles. A tailored arrangement of these fillers was infiltrated with ZA27 alloy in a single-step process. The structure of the FG-MSF contained two individual layers: ZA27/expanded per- lite (EP-MSF) and ZA27/activated carbon (AC-MSF) syntactic foam. The density ofthese FG-MSFs varied between 2.11 and 2.15 g·cm−3. Microstructural studies confirmed that no relevant chemical reaction occurred within the foam, in particular in the vicinity ofthe particle-matrix interfaces. The mechanical properties ofthe produced FG- MSFwere evaluated using quasi-static compression testing. The results showed that the deformationmechanism of the FG-MSF is a mixed mode and varies between the two different filler layers. The energy absorption of the FG-MSF sample was increased compared to uniform syntactic foams containing only a single particle filler.

Impact of particle strength and matrix ductility on the deformation mechanism of metallic syntactic foam

Our manuscript has been accepted for publication in the  Journal of Alloys and Compounds. A free PDF can be downloaded until March 26, 2019.

Abstract: This paper presents a systematic study on the interaction between particle strength, matrix ductility and the deformation mechanism in metallic syntactic foam (MSF). Packed beds of near-spherical NaCl particles (ø2-2.8 mm) were infiltrated with liquid metal to produce the required samples. The brittle zinc alloy ZA-27 and ductile Aluminium (99% Al) were used as matrix materials. NaCl particles were retained inside half of these samples to replicate MSF containing high-strength particles. NaCl was leached from the remaining samples to investigate MSF with weak particles. This procedure ensured that all samples had a near-identical matrix geometry and microstructure, thus isolating the effect of particle strength. Quasi-static compression tests were conducted and significant changes in the deformation behaviour were observed. Samples containing NaCl particles deformed in a shear-band dominated mode, whilst the ductile foam underwent layer-by-layer deformation.

Mechanical and Microstructural Characterization of an AZ91–Activated Carbon Syntactic Foam

Our manuscript Mechanical and Microstructural Characterization of an AZ91–Activated Carbon Syntactic Foam has been published in Materials.

Abstract In this study, activated carbon (AC) particles were combined with AZ91 alloy to manufacture a magnesium syntactic foam. This novel lightweight foam has a very low density, in the range of 1.12–1.18 gcm−3. The results show that no chemical reaction occurred between the AZ91 matrix and the activated carbon particles. The mechanical properties of the foam were evaluated under quasi-static compression loading conditions, and showed a consistent trend for the energy absorption of the fabricated AZ91–AC syntactic foams. The deformation mechanism of samples was a brittle fracture mode with the formation of shear bands during the fracture of all samples.