STUDY INTO THE INFLUENCE OF THE GRAIN STRUCTURE REFINEMENT DEGREE OF ALLOY 6063 INGOTS ON THEIR PLASTICITY, EXTRUSION PARAMETERS AND PROPERTIES OF EXTRUDED PROFILES

The analysis of scientific and technical literature and practical data made it possible to found that changes in casting parameters for ingots using different mold designs allows varying the degree of ingot grain structure refinement in a sufficiently wide range, which should be reflected in the conditions of aluminum alloy profile extrusion as well as physical and mechanical properties of these profiles. Therefore, the purpose of the research was to assess the influence of the degree of grain structure refinement for Alloy 6063 ingots on extrusion deformation and speed parameters and mechanical properties of profiles produced. The study used several batches of Alloy 6063 ingots 178 mm in diameter cast under industrial conditions, as well as profiles obtained by direct extrusion on a 18 MN horizontal hydraulic press subjected to quenching and aging. The grain size in homogenized ingots was estimated by light microscopy using the Olimpus optical microscope, and mechanical properties tests were carried out using the Inspect 20 kN-1 universal test machine. It was found that the initial grain size in the ingot structure exerts a significant influence both on ingot plasticity during extrusion, and on the final structure and mechanical properties of profile products made of aluminum alloys. Having analyzed the results obtained, we can conclude that the increase in strength characteristics of products extruded from ingots with a more refined structure is due to the fact that fine grains are retained in the structure of metal after its deformation, and cast metal plasticity increases with the degree of grain structure refinement in the ingot. This leads to the higher efficiency of profile product hardening and metal outflow rate during extrusion.