APPLICATION OF SECONDARY SHEAR EFFECTS IN THE EXTRUSION MACHINING PROCESS TO EXPLORE RECRYSTALLIZATION MECHANICS DURING CONVENTIONAL EXTRUSION OF 7050 ALUMINUM

摘要

Extrusion machining combines cutting with simultaneous extrusion using an additional constraining tool to induce very large and well-characterized strains. Unlike conventional extrusion, accurate analytical models exist for extrusion machining to calculate values of effective strain, strain rate, and temperature rise as a function of processing parameters. Additionally, the size, shape, and microstructural effects of a secondary shear zone that forms due to friction during extrusion machining have been characterized. This secondary shear zone can be manipulated by varying processing parameters, and can produce a severely inhomogeneous microstructure. This microstructure is also seen during conventional extrusion, as the material on the outside of the extrudate is strained more than the inside material, potentially causing an incomplete recrystallization across the face of the product. The secondary shear effect in the extrusion machining process is utilized to reproduce the inhomogeneous microstructure seen in conventional extrusion in order to better understand the recrystallization behavior during AA7050 extrusion.