An advanced manufacturing process produces nano-structured rods and tubes directly from high-performance aluminum alloy powder, eliminating several steps required during conventional aluminum extrusion processing while increasing product ductility.

Aluminum alloy powders are often used in lightweight components for specialized aerospace applications where cost is not a limiting factor. However, these alloys have typically been too expensive for the automotive industry.

The typical extrusion process requires multiple steps to mass produce the material. Loose powder must be loaded into a can and degassed with a vacuum. The can is then sealed, hot pressed, pre-heated, and placed into the extrusion press. After extrusion, the can is removed to reveal the part.

Researchers from the Pacific Northwest National Laboratory (PNNL) eliminated many of these steps, extruding nanostructured aluminum rods directly from powder in a single step using PNNL's shear assisted processing and extrusion (ShAPE) technology.

In the ShAPE process, a machine forces a rotating extrusion die into aluminum powder in an open container, generating heat at the interface between the powder and die. The material softens and easily extrudes, eliminating the need for canning, degassing, hot pressing, pre-heating, and de-canning.

"This is the first published instance of an aluminum alloy powder being consolidated into nano-structured extrusions using a single-step process,” says PNNL materials scientist Scott Whalen, who led the study. "The elimination of the processing steps and the need for pre-heating could dramatically reduce production time as well as lower the cost and overall embedded energy within the product, which could help automotive manufacturers who want to make passenger vehicles more affordable, lighter, and fuel-efficient for the consumer."

SCM Metal Products Inc. aided the project by providing the aluminum alloy powder and performing mechanical testing to validate the resulting material's performance. PNNL and SCM Metal Products are now collaborating on a project for DOE's Office of Technology Transitions to upgrade the process for larger extrusions.

In addition to eliminating processing steps and reducing heating, the ShAPE process also improved ductility. While high-performance aluminum alloys have excellent strength, they are typically hampered by poor ductility. However, the ductility of the extrusion produced by ShAPE was 2x to 3x that of conventional extrusion products with equivalent strength. The refinement of the second phases in the powder – tiny strengthening particles of non-aluminum materials enabled the improvement. ShAPE reduces the particles to nanoscale sizes and evenly distributes them throughout the aluminum matrix, increasing ductility.

SCM Metal Products Inc.

Pacific Northwest National Laboratory