Investigation into the Influence of the Degree of Grinding of the Ingot Grain Structure of the 6063 Alloy on Its Plasticity, Extruding Parameters, and Properties of Extruded Profiles

As a result of an analysis of scientific and technical literature and practical data, it is found that changing the casting parameters for ingots using different designs of crystallizers makes it possible to vary the degree of refinement of the grain structure of ingots in a sufficiently wide range, which should be reflected in the conditions of extrusion of aluminum alloy profiles and their physicomechanical characteristics. Therefore, the purpose of this research is to assess the influence of the degree of grinding for the ingot grain structure of alloy 6063 on the deformation and speed parameters of extrusion and the mechanical properties of profiles. Several parties of 178-mm diameter ingots of 6063 alloy cast under industrial conditions, as well as profiles formed by direct extrusion using a horizontal hydraulic press with a force of 18 MN subjected to quenching and aging, are used. The grain size in homogenized ingots is evaluated by optical microscopy using an Olimpus optical microscope, and tests of mechanical properties are performed using an Inspect 20 kN-1 universal testing machine. It is established that the initial grain size in the ingot structure strongly affects both the ingot plasticity during extrusion and final structure and mechanical properties of profiled products made of aluminum alloys. When analyzing these results, it is possible to conclude that an increase in strength characteristics of extruded products made of ingots with a more refined structure is due to the fact that a fine grain is retained in the metal structure after its deformation, while the cast metal plasticity rises with an increase in the degree of grinding the grain structure in the ingot. In connection with this fact, an increase in the efficiency of quenching the profiled products and metal outflow rate during the extrusion take place.