PSI - Issue 50

N.F. Morozov et al. / Procedia Structural Integrity 50 (2023) 192–199 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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The displacement of ADC-50 with a dispersed reinforcing phase (DRP) was carried out at the Al:CNTs ratios of 99.9:0.1, 99:1, 99:3, 95:5. The components were mixed on a planetary ball mill PM 100 CM in a steel cup with a volume of 125 ml at 150 revolutions per minute for 10 minutes. Grinding bodies are steel balls with a diameter of 5. The ratio of the mixed material to the grinding bodies was 1:25. The CNTs introduction was carried out in one stage – the components were weighed and then kneaded in one go. This mode of introducing CNTs into the dispersed Al matrix was chosen due to the high plasticity of Al, as well as the inadmissibility of mechanical activation of chemical reactions between Al and CNTs, which lead to embrittlement of the bulk composite. Due to the fact that aluminum used for forming the matrix is an industrial large-tonnage product manufactured in accordance with industrial standards of purity and safety, preliminary, before using Al for forming matrices, the powder was standardized in size, the metal surface was cleaned of oiling agents and anti-tracers. To obtain samples with minimal porosity, a multi – stage pressing - sintering treatment was carried out. No hot pressing was carried out. The use of hot pressing led to the formation of the third phase – aluminum carbide and, as a consequence, to the deterioration of mechanical properties. Pressing and sintering modes were selected based on the conducted research. As the work showed, when initially high loads were applied to the sample, skipping compaction led to elastic compression, the formation of cracks and gas pockets. The modes of pressing and sintering chosen by us, as well as the Ni plating of nanotubes, which in this case are not destroyed by contact with Al, helped to avoid the formation of aluminum carbide and, as a consequence, to the deterioration of the mechanical properties of the samples. Similar processes began to occur at temperatures close to or above the melting point of the Al matrix (700°C). Thus, a pressing and sintering technique was developed, which made it possible to form a monolithic metal matrix with DRP included in it. This is confirmed by the following micrographs and their analysis. The microphotographs below show a section of a metal matrix composite containing CNT (Fig. 3). No nanotubes were found on the surface of the sample. To study the uniformity of the CNT distribution in the samples, an additional study of the distribution of elements on the sample section was carried out (Fig. 3-5). Two phases are visually distinguished in the sample (Fig. 3). The phase with a lower percentage is distributed along the former boundaries of the ASP-50 particles. The particles themselves are tightly packed and represent a single metal matrix without cracks and cavities. Defects (scratches, microchips) formed during the grinding of the cut of the metal matrix composite sample are also visible on the surface of the slot.

Fig. 3. Micrograph of a polished split Al matrix composite containing CNTs coated with Ni.

Fig. 4. The elemental composition of the surface of a metal matrix composite containing CNTs coated with Ni.