The process, which produces nano structured rods and tubes directly from high-performance aluminium alloy powder, has been demonstrated by a team at the US Department of Energy’s Pacific Northwest National Laboratory.
Using a novel Solid Phase Processing approach, the team say they’ve eliminated steps that are required during conventional extrusion processing of aluminium alloy powders whilst achieving a notable increase in product ductility.
The team's research is described in a paper titled High Ductility Aluminium Alloy Made from Powder by Friction Extrusion, published in Materialia.
High-performance aluminium alloys made from powder are used in lightweight components for 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: 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 (decanned) to reveal the extruded part made from consolidated powder.
In this study, the team says it eliminated many of these steps, extruding nanostructured aluminium rods directly from powder in a single step, using PNNL's ShAPE (Shear Assisted Processing and Extrusion) technology.
Extrusion of aluminium alloys directly from powder eliminates canning, degassing, hot isostatic pressing, decanning, and billet pre-heating.
In the ShAPE process, a powder - in this case, an Al-12.4TM aluminium alloy powder - 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," said 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."
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