The Thixocasting of Aluminum Alloy AK7ч Using Billets with Different Initial Structure of Primary Phase

Processy litʹâ, 2019, Tom 137, №5, p.26-31

Abstract

THE THIXOCASTING OF ALUMINUM ALLOY AK7q USING BILETS WITH DIFFERENT INITIAL STRUCTURE OF PRIMARY PHASE

A study was made of the thixocasting process of the AK7u alloy using bilets with different initial structures (dendritic and non -dendritic — rosette-like and globular) primary phases. The initial microstructure (dendritic, rosette-like and globular) of the bilets for thixocasting, as well as the microstructure of shaped castings obtained after thixocasting, are presented. It is shown that after casting using reec/stocks with the in/t/a/ dendritic structure of the primary a/uminUm phase, the structure in the castings remains dendritic. Moreover, dendrites and dendritic fragments are predominantly fused, the lateral branches of the dendrites merge somewhat, and a certain amount of dendrites is deformed. It was found thaf thixocasting of AK7u alloy using 6ilets with an initial rosette-like structure provides shaped castings with a globular structure of the primary phase with a globule size of 80—100 microns. It should be noted that the globular structure of the primary phase obtained after thixocasting in shaped castings is homogeneous and evenly distributed over the entire cross section of the sections. Thixocasting using bilets with the initial globular structure of the primary phase does not lead to structural changes in the shaped casting. At the same time, the size of the globules in the casting increases slightly. The eutectic in shaped castings obtained after thixocasting is characterized 6ya higher degree of differentiation of its structural components compared to the initial bilets. Mechanical tests showed increased ductility of the investigated alloy after thixocasting without additional heat treatment.