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STUDY THE MICROSTRUCTURE OF COMPOSITE MATERIALS PRODUCED BY MIXING AL-SI PARTICLES
Umidbek Turg'unboy o'g'li Xojimatov Fayzulloh Tursunali o'g'li Yoqubjonov
Composite materials based on the Al-Si system are obtained by mixing 5, 10 and 15 wt.% SiC particles into a melt and crystallization under pressure. As a result of crystallization under pressure, the porosity of composite materials has significantly decreased. The presence of SiC particles and the application of solidification pressure led to a refinement of the microstructure. The presence of SiC particles in the composition of the composites led to a faster wear process, and at the same time, a much higher hardness increase compared to the matrix-based alloy.
Keywords: metal-matrix composite materials, Al-Si alloy, silicon carbide, microstructure, kneading, crystallization under pressure, aging kinetics.
INTRODUCTION
In recent decades, alloys based on light metals have been increasingly used in transport engineering due to a significant reduction in weight, and as a result, an increase in the energy efficiency of structures. In addition, the environmental aspect of the use of such materials is also important, since aluminum alloys can be recycled with relatively low energy costs. Due to their high casting and mechanical properties, alloys of the Al-Si-Mg system are among the promising aluminum alloys [1]. Ranganath et al. [2] and Seah et al. [3] showed that with an increase in the content of reinforcing particles from 2 to 6 wt. %, mechanical properties such as tensile strength, yield strength and hardness increase significantly, while ductility and toughness decrease. Uniform distribution of particles in the matrix is necessary to reduce the stress concentration during loading, and as a result, increase the mechanical properties [4].
EXPERIMENTAL TECHNIQUE
To prepare the alloy, industrial grade materials were used: aluminum (99.85 wt %), silicon (99.9 wt %), and magnesium (99.9 wt %). The matrix alloy was obtained by melting in a muffle furnace and pouring into a graphite mold. To obtain composites, SiC particles 35-45 ^m in size were mixed into the melt in the amount of 5, 10, and 15 wt
Andijan machine building institute, assistant xoj imatovumidbek@gmail .com
Magister degree
ABSTRACT
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Composites were obtained by kneading particles into a melt and further crystallization under pressure. The pressure crystallization process was carried out at a temperature of 620°C using a hydraulic press with a maximum force of 100 tons. Analysis of the microstructure of the samples was carried out using X-ray diffractometry in monochromatic copper Ka radiation on a Bruker D8 Advance diffractometer, as well as using the scanning electron microscopy (SEM) method on a Tescan Vega 3 LMH microscope with an X-Max 80 energy-dispersive detector. The density of the samples was determined by the hydrostaticweighing on an analytical balance Vibra AF. Thermal treatment of the composites was carried out in a Nabertherm furnace. After aging, the hardness was measured using an IT5010 hardness tester at a load of 5 kg.
EXPERIMENTAL RESULTS
In the process of crystallization under a pressure of 100 MPa, the density of both the base alloy and composites based on it increases. the porosity of the samples is significantly reduced as a result of crystallization under pressure. This is due to the fact that the pressure on the liquid metal before and during crystallization leads to a decrease in the content of the gas in the melt, which was dissolved in the process of mixing the particles.
The microstructure of the base alloy in the as-cast state and after crystallization under pressure are shown in fig. 1a-b, respectively. The structure of the base alloy is mainly composed of aluminum solid solution and eutectic. The influence of the process of crystallization under pressure is demonstrated in Fig. 3. 1, c-d. It can be seen that a more uniform distribution of particles occurs, and the number of agglomerations and pores decreases. In addition, as a result of this process, the wettability between the aluminum matrix and SiC particles increases, which leads to an increase in the bond between them, and as a result, an increase in mechanical properties.
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CENTRAL ASIAN ACADEMIC JOURNAL ISSN: 2181-2489
OF SCIENTIFIC RESEARCH VOLUME 2 I ISSUE 7 I 2022
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c d
Figure 1. Microstructure of the alloy and composites after kneading: a) Al-Si alloy; b) after crystallization under pressure of Al-Si alloy, c) Al-Si-15% SiC; d) Al-Si-
15% SiC
As can be seen from fig. 2, the hardness value of the composites is higher than that of the base alloy, which is due to the presence in their structure of SiC particles that are harder than the aluminum solid solution. In this case, the maximum value of hardness is reached much faster in composites compared to the base alloy.
Figure. 2. Change in hardness Hv with aging
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CONCLUSION
The microstructure of composites after crystallization under pressure is characterized by lower porosity and a more uniform distribution of SiC particles compared to composites obtained by casting after mixing the particles into the melt. The addition of particles to the structure of the matrix alloy accelerates the aging process. Micro- and nano-scale crystal lattices of Al-Si composite materials and their microstructure were sufficiently analyzed and studied through this work.
REFERENCES
1. Mamirov, A. M., and I. T. Xojimatov. "Anarboyev II Prospects for the creation of modern solar ovens." Materials of the XII International scientific and practical conference of young scientists «Innovative development and the requirement of science in modern Kazakhstan» Taraz. 2019.
2. Olimov Lutfiddin Omanovich, and Xojimatov Islombek Turg'unboy o'g'li. "MAGNETIC PROPERTIES OF SUBSTANCES." Scientific progress 3.2 (2022): 357359.
3. https://cyberleninka.ru/article/n7issledovanie-struktury-i-svoystv-kompozitsionnyh-materialov-na-osnove-modifitsirovannyh-viskoznyh-tehnicheskih-nitey
4. Muxammadamin o'g'li, Mamirov Abduvoxid, and Xojimatov Umidjon Turg'unboy o'gli. "Determine the amount of heat accumulated at the focal point of the solar oven." Texas Journal of Multidisciplinary Studies 5 (2022): 161-164.
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