OBRABOTKAMETALLOV technology Vol. 25 No. 4 2023 To obtain these rare properties researchers have tried to create various types of metallic foam from different metals and alloys such as steels, Cu, Al, Al-Si, Al-Mg, Pb, Fe, Ni3A1, Mg, Zn, and Ti, Al-Cu, MMCs, metallic glasses etc. Among this variety, aluminium foam has received enormous development in industrial production [2]. Foamed metals are widely used in various industries, such as automotive and aerospace ones due to good mechanical properties and light weight. Aluminum foam has the ability to absorb the shock and vibration due to its closed cell porosity nature. It has good thermal and sound insulation properties. Metallic foam or aluminum foam should be produced using processes that require less capital investment and are the safest. Methods for producing metallic foam There is various methods to produce metallic foams, for example, molten metal method, deposition technique, by powder metallurgy which has been mentioned in fig. 1. Fig. 1. Metal foam production methods [3] Production of metal foam from molten metal This method is commonly used to make metal foam from molten metal due to its cost-effectiveness and simplicity. In this method, the first step is to prepare the molten metal. To obtain a closed cell porous material from molten metal a certain amount of foaming agent or gas injection into the molten material with a stabilizing material (SiC, Al2O3) is required to increase the viscosity of the molten metal [4]. Solid-gas eutectic solidification. Investment casting method and syntactic foaming using filler material are also used by the researcher are also used by researchers to produce metal foam from molten metal. Selection of method depends on the required porosity, relative density and other factors, as these vary from method to method. Porosity of 80–97 % can be obtained in the metallic foam by the gas injection method, foaming agent method. Porosity of 5–75 % porosity is not very high, but it can be achieved in metal foam through gas-eutectic reaction. This was studied by Banhart. The final porosity depends on the processes and controlled parameters such as stirrer’s revolutions per minute, stirring time, foaming agent, amount of foaming agent, choice of gases for the injection method, such as argon or neon. To obtain the best result, many researchers have optimized these parameters. Producing metal foam by injecting gas into molten metal In this process, metallic foam is produced by injecting suitable gas into the prepared molten metal. The gas injection method is not suitable for easily oxidizable material (Mg, Ti), but aluminum foam is widely
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