EAGER: Hot Extrusion of High-Strength Aluminum Alloys with Rotary Porthole Dies

Northwestern University, Evanston IL

Investigators

Abstract

Due to their outstanding strength-to-weight ratios, high-strength aluminum alloys are widely used in the automotive, defense, and aerospace industries, as well as in construction and anywhere weight savings are desired. Among the different manufacturing methods used on these materials, hot extrusion is the most efficient production process to produce parts with a constant cross-section. However, even at very high temperature, some attractive aluminum alloys have very low extrudability, limiting their wider application. This EArly-concept Grant for Exploratory Research (EAGER) project is intended to solve this problem by exploring the feasibility of a new hot extrusion process with a rotary porthole die. If successful, the research will be expanded to investigate performance of a wider range of alloys, which ultimately will increase production rate of high-strength aluminum. The fundamental scientific and technological advances made will also be applicable to other difficult-to-extrude alloys. Because superior aluminum alloys could then be used across many industries, greater weight savings than is currently possible would become routine. In addition, because extrusion is a near net-shape process, finishing operations would be reduced and the cost of these aerospace alloys could decrease. This project will deliver a new extrusion method and scientific findings for improving the extrusion of aluminum alloys, and create a model for extruding other difficult-to-extrude alloys, via metal flow control. Since the full-scale exploration of the envisioned rotary porthole die concept is associated with high risk and cost, in this EAGER project the concept a rotary porthole die will be demonstrated through a set of stationary twist-grove dies. In previous work, in-process material microstructural changes have been observed in conventional porthole dies. This finding suggests that a rotary porthole die might allow the control of the material flow to impart microstructural changes, resulting in production improvements. This research will involve the production of a testbed for with a twist-groove porthole die to demonstrate the process. At the same time, modeling will be performed to investigate metal flow in rotating porthole dies. The understanding of the metal flow path and its effects on microstructure, as a function of process variables such as temperature and deformation, will enable the control of the mechanical properties of the extruded products and increase the process efficiency. The goal is to provide a proof-of-concept of this new manufacturing process, which then provides a path for widespread use of difficult-to-form lightweight alloys.