Structure and phase composition formation of cast aluminum matrix composites during multiple remelting

Abstract

The lack of understanding as to the nature of interfacial interaction between reinforcing particles and the matrix alloy during repeated remelting of cast composite materials is one of the problems hindering the expansion of their industrial application. This research 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 is not accompanied by any new phases appearing at the interfaces between particles and the matrix, which indicates the stability of the SiC reinforcing phase in aluminumsilicon melts under the considered temperature-time and concentration conditions. Repeated remelting of aluminum matrix composites with silicon carbide shifts the particle distribution uniformity towards a more uniform distribution degree (on average 0.81046 at the first remelting iteration, 0.6901 at the second one and 0.5609 at the third one) and slightly reduces their average sizes (from 70.74 μm at the first iteration to 65.76 μm at the second one and 61.21 μm at the third one), apparently due to particle fragmentation that leads to an increase in the quantity of finer particles. At the same time, the share of the area occupied by particles in the section regions under consideration remains practically unchanged (10.9293, 10.9607 and 11.6483 % at the first, second and third remelting iterations, respectively). In the course of repeated remelting of Al–SiC aluminum matrix composites, processes of reinforcing particle redistribution occur that lead to the destruction of agglomerates even without intensive mixing with an impeller. Due to this, the uniformity of particle distribution in the structure of secondary aluminum matrix composite ingots can be significantly improved.