Issue 50

I. Papantoniou et alii, Frattura ed Integrità Strutturale, 50 (2019) 497-504; DOI: 10.3221/IGF-ESIS.50.41 504 C ONCLUSIONS hile aluminium foams were manufactured using powder metallurgy route with gas releasing particles, the effect of aluminium powder morphology, precursor compaction pressure and foaming temperature were examined. The porosity-time (P f-t ) and the foaming efficiency (η) diagrams were obtained. Furthermore, the foams with the para- meters resulting to the highest foaming efficiency were subjected to compaction tests. Concerning the powder morphology, it was concluded that in all tests the foams with the fine aluminium powder exhibited higher foaming efficiency than the foams with coarse aluminium powder. The precursors with aluminium flakes collapsed just after the extrusion from the die. As far as it concerns the compaction pressure/foaming temperature, the highest foaming efficiency was observed for pre- cursors with compaction pressures higher than 700 MPa and high foaming temperatures of 750 o C and 800 o C. The speci- mens with 800 o C sintering temperature introduced a slightly higher foaming efficiency and foaming rate but collapsed sooner than the specimens with 750 o C. The compression tests with the specimens with the parameters that resulted to the higher foaming efficiency provided stress-strain curves characterized by the typical initial elastic response, followed by a deformation plateau with a positive slope and finally a transition to densification. The plateau region was very smooth and showed no oscillations which are typically associated with local failure of cell walls. The compression strength at the beginning of the plateau region was 5 MPa and the stress variations in the elastic regime were found to be nearly linear. R EFERENCES [1] Gibson, L. and Ashby, M. (1997). Cellular Solids, Structure and Properties, 2nd ed. Cambridge University Press, UK. [2] Ashby, M., Evans, A., Fleck, N., Gibson, L., Hutchinson J., Wadley, H. (2000). Metal Foams: A Design Guide. Butterworth-Heinemann, USA. [3] Banhart, J. (2001). Manufacture, characterization and application of cellular metals and metal foams, Progress in Materials Science 46, 559-632. [4] Michailidis, N., Stergioudi, F., Tsouknidas, A. (2011). Deformation and energy absorption properties of powder- metallurgy produced Al foams, Materials Science and Engineering: A 528,7222-7227. [5] Laughlin, D., Hono, K. (2013). Porous Metals. Physical Metallurgy, 5th ed., Elsevier, Amsterdam. [6] Salimon, A., Brechet, Y., Ashby, M., Greer, A. (2005). Potential applications for steel and titanium metal foams, Journal of Materials Science 40, 5793-5799. [7] Davies, G., Zhen, S. (1983). Review Metallic foams: their production, properties and applications, Journal of Materials Science 18, 1899-1911. [8] Allen, B., Sabroff, A. (1963). Method of making foamed metal. US Patent 3,087,807. [8] Duarte, I., Banhart, J. (2000). A study of aluminium foam formation – kinetics and microstructure, Acta Materialia 48(9), 2349-2362. [9] Baumgärtner, F., Duart, I., Banhart, I. (2000). Industrialization of powder compact foaming process, Advanced Engineering Materials 2, 168-174. [10] Shiomi, M., Imagamab, S., Osakada, K., Matsumoto, R. (2010). Fabrication of aluminium foams from powder by hot extrusion and foaming. Journal of Materials Processing Technology 210, 1203-1208. [11] Kitazono, K., Sato, E., Kuribayashi, K. (2003). Novel manufacturing process of closed-cell aluminum foam by accumulative roll-bonding, Scripta Materialia 50, 495-498. [12] Papantoniou, I., Kyriakopoulou, E., Pantelis, D., Athanasiou-Ioannou, A., Manolakos, D. (2018). Manufacturing process of AA5083/nano-γAl2O3 localized composite metal foam fabricated by friction stir processing route (FSP) and microstructural characterization, Journal of Materials Science 53, 3817-3835. [13] Lazaro, J., Solorzano, E., de Saja, J.A. (2012). Early anisotropic expansion of aluminium foam precursors, J Mater Sci 48, 5036–5046. [14] Strano, M., Pourhassan, R., Mussi, V. (2013). The effect of cold rolling on the foaming efficiency of aluminium precursors, Journal of Manufacturing Processes 15, 227-235. [15] Shim, C., Yun, N., Yu, R., Byun, D. (2012). Mitigation of Blast Effects on Protective Structures by Aluminum Foam Panels, Metals 2(2), 170-177. W