FORMATION OF A NON-DENDRITIC STRUCTURE OF THE PRIMARY PHASE IN A CASTING FROM AN ALUMINUM ALLOY AK7ч WHEN POURING THE MELT INTO A MOULD WITH DIFFERENT GATING-FEED SYSTEMS
Procesi littâ, 2023, Vol 4 (154), 36-43
DOI:
https://doi.org/10.15407/plit2023.04.036Keywords:
aluminum alloy, mould, gating-feed systems, alloy flow, non-dendritic structure, globular structure, primary phase, crystallization centersAbstract
The paper shows the possibility of forming a non-dendritic globular structure of the primary phase in a casting of aluminum alloy AK7ч in a mould, which combines different types of gating-feed systems – upper (rain), lower (siphon) and vertically slotted. To create these three types of gating-feed systems in one mould, its cavity was divided into four compartments of equal volume using two perpendicular thin metal partitions. Each compartment of the mould was assigned a clockwise sequence number from I to IV. The first compartment was isolated and not connected to other compartments. The second compartment was connected to the third compartment using the lower feeder. In turn, the third compartment was connected to the fourth compartment using a vertical slot feeder. The melt was poured onto a metal thin partition between the first and second compartments so that three times less melt entered the first compartment than into compartment II. Such pouring of the mould ensured the uniformity of its filling and the simultaneous filling of the first (isolated) compartment and compartments II-IV (compartments that are interconnected by gating channels). The aluminum melt was poured into the cavity of the mould in the high superheated (Tpour = 700 oC) and low superheated (Tpour = 620 oC) states. It is shown that when pouring a mould with a high superheating melt, a dendritic structure of aluminum solid solution with an average value of the dendritic parameter of 32 μm is formed in all four compartments of the mould. It was established that as a result of pouring the melt into a mould with low superheating, a non-dendritic structure of the primary solid phase was formed in the first, second, third and fourth compartments of the mould. At the same time, in the fourth compartment of the mould, the indicated non-dendritic structure of the α-Al phase had the form of a globular one with a size of globular crystals of 50–100 μm.
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