Researchers at the Pacific Northwest National Laboratory (PNNL), Richland, Washington, USA, have reportedly developed a new manufacturing process for the production of rods and tubes directly from high-performance aluminium alloy powder in a single step. Using a Solid Phase Processing approach, the research team stated that they have been able to eliminate several steps required during conventional extrusion processing of aluminium alloy powders, while achieving a significant increase in product ductility.
This is expected to have significant benefits for sectors such as the automotive industry, where the high cost of manufacturing typically limits the use of high-strength aluminium alloys made from powders. The team’s research is described in a paper published in the June 2019 edition of Materialia, titled High Ductility Aluminum Alloy Made from Powder by Friction Extrusion.
High-performance aluminium alloys made from powder have long been used in lightweight components for specialised aerospace applications, where cost is not a limiting factor. However, these alloys have typically been too expensive for the automotive industry.
A typical extrusion process for aluminium alloy powders is energy- and process-intensive, requiring multiple steps to mass-produce the material. First, the loose powder must be loaded into a can and degassed. The can is then sealed, hot pressed, pre-heated, and placed into the extrusion press. After extrusion, the can is removed to reveal the extruded part made from consolidated powder.
In this study, the team eliminated many of these steps, extruding nanostructured aluminium rods directly from powder in a single step using PNNL’s Shear Assisted Processing and Extrusion technology, or ShAPE™. In the ShAPE process, a powder – in this case Al-12.4TM aluminium alloy powder provided by SCM Metal Products, Inc., a division of Kymera International – is poured into an open container.
A rotating extrusion die is then forced into the powder, which generates 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 decanning.
“This is the first published instance of an aluminium alloy powder being consolidated into nanostructured extrusions using a single-step process like ShAPE,” stated PNNL Materials Scientist Scott Whalen, who led the study. “The elimination of both 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 be beneficial for automotive manufacturers who want to make passenger vehicles more affordable, lighter, and fuel-efficient for the consumer.”
Besides providing the Al-12.4TM powder, SCM Metal Products performed 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 scale up the process for larger diameter extrusions.