Advanced Aluminum Alloy: Extruded Thin Wall Structural Concepts

The primary objective of this proposed work is to develop a method of producing integrally stiffened, complex shaped monolithic structural components in high strength aluminum alloys at a lower cost and lighter weight than equivalent conventional built-up assemblies. In Phase I the feasibility of attaining this objective will be demonstrated by conducting a series of subscale experiments based upon a uniquely devised processing sequence that involves several advanced processing methods including: 1)Equal Channel Angular Extrusion (ECAE), 2)Superplastic Extrusion (SPE), 3)Stretch Straightening and, 4)Creep-Age Forming. ECAE offers a novel deformation approach to processing a large number of materials to obtain a variety of useful microstructures, including submicron grain sizes in thick sections. With the submicron grain sizes, certain high strength aluminum alloys can be formed or extruded superplastically into very thin cross section panels. The aluminum alloy flow stresses at working temperatures in the submicron/SPE process are much lower than in conventional extrusion. This allows more fragile extrusion dies thus allowing thinner section details and larger overall extruded panels for a given press capacity. ECAE process optimization experiments will be conducted on a selected aluminum-lithium alloy to produce submicron grain structure. Advance Technology Assocates (ATA) will subcontract SPE and Creep Age Forming experiments to Rockwell International Science Center (RISC).