Production of Closed-Cell Foams Out of Aluminum Chip Waste: Mathematical Modeling and Optimization

Abstract

The main aim of this research is to mathematically describe the influence of the processing parameters of metal foam production from machining chip waste. Using this method, metal foams were produced without a remelting step, which should be both economically and environmentally effective. Firstly, expensive metal powders were replaced with waste in the form of machining chips. Secondly, machining chip waste was recycled without any significant material losses, which usually occurs during conventional recycling (using the melting process). To describe the innovative process and to relate metal foam properties to foaming temperature, the blowing agent weight percentage, and foam density (controlled by foaming height), response surface methodology, and the design of experiments were used. The quality of the produced metal foams was evaluated by determination of density, yield strength, compression strength, plateau stress, energy absorption, pore perimeter, and pore inhomogeneity for specimens obtained following the experimental plan. It was proven that pore inhomogeneity increased in the range from 1.41 to 4.81 mm with a higher temperature and the addition of a foaming agent. However, higher energy absorption and yield strength were obtained with a higher temperature but a lower percentage of TiH2. Despite the production from machining chips, pores were homogenous without significant cracks. These kinds of metal foams are comparable to commercial foams made of metal powders.