Studies on hot extrudability of aluminum and 6063 alloy cast billet due to working pressure and structural flow

Abstract

The macro-structural flow during deformation of metals was observed in the extrusions of commercially pure aluminum and 6063 alloy at 500°C under farious extrusion conditions. The deformation behavior concerning the extrusion pressure and the macro-structure obtained by experiments was discussed with respect to the effects of ram speed, die angle, and reduction in diameter.The following results were obtained:(1) As for a given extrusion ratio (R) an approximate linear relationship was empirically obtained between extrusion pressure (P) and logarithm of (R). As for a given extrusion velocity (V), there also existed an approximate relationship between logarithm of (P) and logarithm of (V). Each factor expressing the ratio between the values in these relationships depended upon extrusion conditions such as extrusion ratio and extrusion speed. When extrusion pressures were measured for three die angles, the value of (P) was smaller with the increase of die angle (α).(2) The flow of the macro-structure of cast billet during the extrusion process could be divided into the following zones; dead metal, inner shearing, entry to the die, neck of the die, extruded product, etc. It was found that the extrusion characteristics of cast billets could be explained with respect to the grain refining behavior of structures in these zones.(3) The microscopic examination of the structure and etching figures showed that the feathery grains having a twin plane of (111) were converted into granular grains having a plane of (110) during hot dynamic extrusion at 500°C. However, the mechanism of the rotation of these deformed crystals remained still unsolved.