Improved Stability of Aluminum Foam Through Heat Treatment of Foamable Precursor
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Improved Stability of Aluminum Foam Through Heat Treatment of Foamable Precursor Fan Deng1,2 · Yanqiang Liu2 · Xuehan Lu2 · Jianzhong Fan2 Received: 6 June 2019 / Accepted: 5 August 2019 © The Korean Institute of Metals and Materials 2019
Abstract Foam stability, characterized by the dynamics of foam expansion and decay, is essential for producing aluminum foam. While, the stability is often difficult to control. In present study, the heat treatment of foamable precursor was applied to improve the foam stability via the powder route. Interestingly, both process of foam expansion and decay were remarkably slow down after heat treatment. The time to achieve peak expansion was prolonged to 2.38 times, and the time span from peak expansion to obvious drainage and collapse happening increased to 6 times. The enhanced stability is thought to relate to the oxide-flakes on the cell face caused by heat treatment. Keywords Aluminum foam · Stability · Powder metallurgy · Heat treatment · Precursor Aluminum foams have outstanding physical and mechanical properties such as low density, high specific stiffness, high energy absorption capability etc. [1–4]. Aluminum foams can be produced by foamable precursors, either from powder metallurgy or melting technology [5]. In traditional powder metallurgy process, the foam expansion is always violent and unstable, with lifetime of minutes. Also the liquid metal foams are unstable, and can stand only in a short time, followed by rapid drainage, coalescence and coarsening [5, 6]. Consequently, preparation procedure is difficult to control, leading to an unsatisfactory pore structure, i.e. nonuniform pore size distribution, apparent density gradient, and defects in cell wall. In a word, the stability of metal foams is still an open question. Electronic supplementary material The online version of this article (https://doi.org/10.1007/s12540-019-00419-8) contains supplementary material, which is available to authorized users. * Yanqiang Liu [email protected] * Jianzhong Fan [email protected] 1
Beijing General Research Institute for Nonferrous Metals, National Engineering and Technology Research Center for Non-Ferrous Metals Composites, Beijing 100088, China
GRIMAT Engineering Institute Co., Ltd., National Engineering and Technology Research Center for Non-Ferrous Metals Composites, Beijing 101407, China
2
As well known, melting metal is hard to be foamed without any inclusions [7]. Hence, solid particles always are added to improve the foamability, to make relatively stable aluminum foams. In the melting route, calcium as thickening agent is used to increase the viscosity and make the melt foamability [8]. Besides, ceramic particles with optimized size and volume fraction (up to 10–20%) are thought to play an important role in stabilization of foam, and give birth to superior pore structure [7, 9]. In powder route, oxide particles, formed by fracture of the powders’ oxide layers [10–12], are found to be the primary factor that dominate the foam stability. But the fundamental ro
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