The energy intensity and attendant carbon dioxide emissions associated with aluminum (Al) mining and refining can be alleviated with an emerging process designed to exploit post-consumer scrap Al. The technology developed at the U.S. Pacific Northwest National Laboratory can convert discarded Al into usable structural extrusions that meet or exceed stringent ASTM standards for strength and flexibility for common building-grade alloys.

Energy savings approach 90% with a process that transforms post-consumer aluminum into high-grade building components. Source: U.S. Pacific National Northwest Laboratory

The Shear Assisted Processing and Extrusion Process (ShAPE) is intended to reduce dependency on imported or virgin Al to supply components for the building sector. The resulting energy savings will enable users to meet or exceed standards for energy-efficient buildings.

The process deforms scrap Al bricks or rod-shaped billets using heat generated by high shear forces to pulverize impurities in the scrap into tiny particles and uniformly disperse them within the Al microstructure. The technique eliminates the potential for the formation of microfractures commonly encountered in recycled Al products manufactured using conventional methods. ShAPE also provides for substantial energy savings by eliminating the need to dilute impurities found in recycled Al.

“The ShAPE manufacturing process conserves energy and eliminates greenhouse gas emissions on several fronts,” said chief scientist Scott Whalen. “First, we avoid the need to add primary aluminum. Then, we eliminate the need for what is called homogenization of the billet material, a 6- to 24-hour heat treatment near 500° C prior to extrusion.”

The mechanical properties of rods, tubes and irregular hollow, multichannel trapezoids made from post-consumer scrap briquettes were tested under mechanical stress. The ShAPE-produced materials were documented to perform at or above ASTM standards for yield strength and ultimate tensile strength.