By Alexandra Freibott
Lighter vehicles can travel farther with less energy, driving demand for lighter automotive components. High-performance aluminum alloys, such as 7075, are some of the lightest and strongest options, but they require energy-intensive production which increases costs and therefore limits their use.
To research from Pacific Northwest National Laboratory (PNNL) cut that energy in half with a more efficient process to manufacture high performance aluminum components. With support from the Department of Energy’s Office of Advanced Manufacturing, the researchers determined that the Shear-Assisted Processing and Extrusion (ShAPE™) The technology can eliminate heat treatment steps in the production process, resulting in significant energy savings and reduced emissions. ShAPE is a green and affordable manufacturing approach that enables wide use of high performance aluminum alloys in automotive applications.
A Recipe for Next Generation Metalcrafting
Much like baking a cake, metal crafting relies on well-mixed ingredients and lots of heat. Conventional metal production uses heat to melt individual metals and alloying elements, such as aluminum, copper, or magnesium, together to create alloys that are lighter, stronger, or easier to form. If these elements are not mixed well, cracks and fractures can form during processing and compromise the properties of the final product, as an improperly mixed and lumpy cake batter will result in a disastrous crumbled cake. In the production of metals, heat is used to ensure that the individual metal elements of an alloy are well mixed during a step called homogenization.
During homogenization, large metal castings called billets are heated to nearly 500 degrees Celsius, or about 900 degrees Fahrenheit, for up to 24 hours. This heat treatment step dissolves alloy aggregates – similar to lumps in cake batter – in the billet to ensure that all metallic elements are evenly distributed or homogenized. This improves the performance of the final product. After homogenization, the metal rods undergo additional heating and forming in a step called extrusion.
“Homogenization is the most energy-consuming step in the entire metal extrusion process,” said Scott WhalenChief Materials Scientist at PNNL and co-developer of ShAPE.
The ShAPE machine eliminates the need for separate homogenization and extrusion steps by combining heating and deformation, i.e. changing the shape of the metal itself. In the ShAPE machine, the metal billet is simultaneously pushed through a small opening into a spinning die. Together, the rotational motion and deformation carefully blend the metal elements as they are extruded. Essentially, the ShAPE process homogenizes the metal billet in seconds, just before it is extruded. This eliminates the need for a day-long preheat homogenization step and means no additional energy is used to heat the billet during extrusion. Together, this translates to up to 50% energy savings using ShAPE.
Take your cake and eat it too
Not only ShAPE more energy efficient and faster process, but it also improves the quality of mixing the individual alloying elements, leading to a better end product. As a lumpy batter can ruin a cake, the end product of extrusion manufacturing often works best when the elements are well mixed together. Performance testing has shown that aluminum alloy components treated with ShAPE exceed current American Society for Testing and Materials standards for strength and elongation.
“We took a closer look using an electron microscope and saw that ShAPE breaks up the alloy aggregates and dissolves them into the aluminum matrix before extrusion, making it more extrudable,” said declared Tianhao Wangmaterials scientist at PNNL and lead author on recent publication in Materials and design. “This translates to better performance – our 7075 aluminum alloys are stronger and stretch more before breaking.”
Putting high-performance aluminum alloys at your fingertips
Aluminum alloys are popular in the automotive and aerospace industries because they are strong and lightweight. Manufacturing the highest performing aluminum alloys is time-consuming and energy-intensive, putting them out of many markets, such as applications in passenger vehicles. The ShAPE process removes a major barrier in the production of high performance aluminum alloys by dramatically reducing energy consumption and greenhouse gas emissions during manufacturing.
“This is an important step in unlocking the potential of next-generation metal fabrication to produce better, cheaper and greener products for the future,” Whalen said.
This research was supported by the Department of Energy’s Office of Advanced Manufacturing and performed using a specially designed ShAPE machine manufactured by BOND Technologies, Inc. The process, tooling and techniques ShAPE are available for licensing (contact Sara Hunt, Marketing Manager).
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