An advanced manufacturing process was developed to produce nano-structured rods and tubes directly from high-performance aluminum alloy powder in a single step. Using a Solid Phase Processing approach, researchers eliminated several steps that are required during conventional extrusion processing of aluminum alloy powders and achieved a significant increase in product ductility (how far a material can stretch before it breaks).
High-performance aluminum alloys made from powder have long been 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. A typical extrusion process for aluminum 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 gases removed using a vacuum, called “degassing.” The can is then sealed, hot-pressed, pre-heated, and placed into the extrusion press. After extrusion, the can is removed, or “decanned,” to reveal the extruded part made from consolidated powder.
The new process 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 powder — in this case, an Al-12.4TM aluminum 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.
While high-performance aluminum alloys have historically shown excellent strength, they have typically been hampered by poor ductility; however, the team found dramatic improvements in the ductility of the extrusion produced by ShAPE, measuring ductility that is two to three times that found in conventional extrusion products, and with equivalent strength.
Transmission electron microscopy was used to evaluate the microstructures of the powder and the extruded materials. The results indicated that the ShAPE method refined the second phases in the powder — tiny strengthening particles of non-aluminum materials. ShAPE reduces the particles to nanoscale sizes and evenly distributes them throughout the aluminum matrix, increasing ductility.