OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 25 No. 4 2023 deposition and physical vapor deposition have also been used to produce more exotic foam [3]. Foam can be defined as a uniform diffusion of the gas phase in a liquid, while the cells and pores formed in the liquid, characterized by very thin films separating it. This structure provides relatively high stiffness and strength with low density and is used where it is necessary to significantly reduce the weight of the structure. The shape and size of the cells depend on the function of the structure and determine the effectiveness of the latter. Metal foam with an open structure absorbs the energy of compression strain well compared to metal foam with closed pores. The structure also resists sudden fracture well. Metallic foams can be divided into two categories: with closed pores and with open pores. For the production of the first category, the melting method or the powder metallurgy method is used. Generally, the melting method is a casting method that is used to produce metal foam with closed pores, whereas powder metallurgy is used to produce metal foam with open pores. Metal foam with closed pores can be obtained by three methods: by adding a blowing agent, by injecting an inert gas into the molten metal, and by a gas-eutectic reaction [4]. These processes require high initial investments. In powder metallurgy, a space holder technique and a foaming agent are added to the metal powder. The purpose of the development of metal foam is to obtain unique properties such as high stiffness, low specific weight, high gas permeability, low thermal conductivity, high impact absorption capacity, and electrical insulation. Various metal foams are developed from metals and alloys such as Al, Al-Si, Al-Mg, Cu, Pb, Fe, Steel, Ni3A1, Zn, Mg, Ti, Al-Cu, MMC, metal glasses, etc. Among them, aluminium foam has received a tremendous development in industrial production. Aluminium metal foam was developed using calcium carbonate as a foaming agent. The amount of calcium carbonate added to the composition for the formation of metal foam was 2.5 wt. % [6]. The density of the obtained material was 848 kg/m3, the relative density was 0.342 [5]. The zinc content in aluminium foam with closed cell and the study of the effect of zinc on aluminium foam material. The results showed that aluminium foam, which contains 4 wt. % Zn, has a better yield strength and a longer plateau section than aluminium foam, which does not contain zinc. Aluminium foam is fabricated by foaming the melt [7]. Two aluminium foam materials were fabricated by powder metallurgy using calcium carbonate and TiH2. Calcium carbonate as a foaming agent demonstrates greater stability compared to TiH2, therefore calcium carbonate is an expensive and effective gas-generating agent [8]. Zinc-aluminium alloy foam was obtained by stir casting method, and calcium hydride (CaH2) was used as a foaming agent. The density of the resulting material varies from 0.25 g/cm3 to 0.45 g/cm3, and the porosity of 94 % is achieved in aluminium alloy foam metal by stir casting [9]. The melt route method is superior to other methods in terms of the required amount of capital and various requirements for the desired final form [10]. Improving the stabilization of aluminium foam and its cellular structure in the production process through the use of coated calcium carbonate as a foaming agent. It is not necessary to additionally introduce a stabilizer into the molten metal, since a material that increases viscosity is formed during decomposition [11]. Based on the thermal decomposition and cellular structure, a foaming agent is added to the material [12]. It is noted that the temperature and mixing speed are the dominant parameters determining the ability of energy absorption by aluminium foam [13]. Aluminium metal foam is fabricated by the melt foaming method, and exhibits its mechanical properties under repeated impact load. The test results showed that the degree of damage to aluminium foam increases with an increase in the number of impacts [14]. Metal aluminium foam with open cells was developed using a steel mesh structure. In this study, the arrangement of cells is considered an important parameter for controlling mechanical properties [15]. For the manufacture of aluminium syntactic foams, the method of cold chamber die casting was used. The density of such foam material varied from 1.17 to 1.5 g/cm3 and it was found that the foam material subjected to heat treatment becomes more brittle [16]. The open-pore material is made of biodegradable magnesium alloy through infiltration technique. Its porous structure is similar to that of a gyroid. Tests have shown that the Young’s modulus of the obtained open-pore material is similar to the Young’s modulus of the human trabecular bone [17].
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