Formation of the Structure and Phase Composition of Cast Aluminum Matrix Composites during Multiple Remelting

Abstract

Insufficient understanding of the nature of the interfacial interaction of reinforcing particles with the matrix alloy during repeated remelting of cast composite materials is one of the problems that limit the increase in the volume of their industrial application. This work is aimed at establishing the effect of repeated remelting of AK12 + 10 vol % SiC aluminum matrix composites on the retention and chemical stability of silicon carbide reinforcing particles. It is shown that an increase in the number of remelting iterations was not accompanied by the appearance of new phases at the interfaces between particles and the matrix, which indicates the stability of the SiC reinforcing phase in aluminum–silicon melts under the considered temperature–time and concentration conditions. During repeated remelting of aluminum matrix composites with silicon carbide, the degree of particle distribution uniformity shifts toward a more uniform distribution (on average 0.81046 at the first iteration of remelting, 0.6901 at the second, and 0.5609 at the third) and some decrease in their average sizes occurs (from 70.74 µm at the first iteration to 65.76 µm at the second and 61.21 µm at the third), apparently owing to particle fragmentation, leading to an increase in the amount of a finer fraction. At the same time, the share of the area occupied by particles in the segments of the section under consideration remains practically unchanged (10.9293, 10.9607, and 11.6483% in the first, second, and third iterations of remelting, respectively). In the course of repeated remelting of aluminum matrix composites of the Al–SiC system, processes of redistribution of reinforcing particles occur, leading to the destruction of agglomerates even in the absence of intensive mixing by an impeller. Because of this, the uniformity of particle distribution in the structure of ingots of secondary aluminum matrix composites can be significantly improved.