MMaterialsgateNEWS 2015/05/13

Lightweight Design: Out with heavy metal

New, high-volume joining process expands use of aluminum in autos

Researchers have demonstrated a new process for the expanded use of lightweight aluminum in cars and trucks at the speed, scale, quality and consistency required by the auto industry. The process reduces production time and costs while yielding strong and lightweight parts, for example delivering a car door that is 62 percent lighter and 25 percent cheaper than that produced with today's manufacturing methods.

In partnership with General Motors, Alcoa and TWB Company LLC, researchers from the Department of Energy's Pacific Northwest National Laboratory have transformed a joining technique called friction stir welding, or FSW. The technique now can be used to join aluminum sheets of varying thicknesses, which is key to producing auto parts that are light yet retain strength where it's most needed. The PNNL-developed process also is ten times faster than current FSW techniques, representing production speeds that, for the first time, meet high-volume assembly requirements. The advancement is reported in the May issue of JOM, the member journal of The Minerals, Metals & Materials Society.

"We looked at the barriers preventing the use of more lightweight alloys in cars, picked what we felt was a top challenge, and then formulated a team that represented the entire supply chain to tackle it," said Yuri Hovanski, the program manager at PNNL and lead author. "The result is a proven process that overcomes the speed, scale and quality limitations of FSW that previously were showstoppers for the auto industry."

The two-phase, six-year project is funded by the Department of Energy's Office of Energy Efficiency and Renewable Energy with in-kind partner contributions from each of the participating companies.

Aluminum can't take the heat

To create door frames, hoods and other auto parts, sheets of metal are welded together end-to-end into a "tailor-welded blank" which is then cut into appropriate sizes before being stamped into the final shape. This process allows a high degree of customization. For example, a thicker gauge of metal can be used on one side of a car part, where extra strength is needed, joined via a weld to a thinner gauge on the side where it's not.

Conventional laser welding works great to join varying thicknesses of steel, but can be problematic when applied to aluminum due to the reactivity of molten aluminum to air. Instead, manufacturers today must create several components from single sheets that are then riveted together after being stamped, resulting in additional production steps and more parts that drive up cost and weight.

"Reducing the weight of a vehicle by 10% can decrease fuel consumption by 6%-8%, so the auto industry is very interested in a welding technique such as FSW that is aluminum friendly," Hovanski said.

Mixed, not melted

A friction-stir welding machine looks and acts like a cross between a drill press and a sewing machine. Lowered onto two metal sheets sitting side-by-side, the "drill bit," or in this case pin tool, spins against both edges. As it travels along, the pin creates friction that heats, mixes and joins the alloys without melting them. By auto industry production standards, however, the process was too slow - just one-half meter welded per minute - which is why the technique has been used only in niche applications, if at all.

Supply chain success

Hovanski and colleagues at PNNL initially compared several joining techniques before selecting FSW, which was the only one to pass all of GM's rigorous weld quality specifications. Researchers then conducted a comprehensive series of lab-scale welding tests on aluminum sheets provided by Alcoa.

In all, dozens of unique tool designs with varying shapes, lengths and diameters of the pin were created. These were assessed against a variety of weld parameters, such as the depth, rotation speed and angle of the tool. Through statistical analysis, the team identified the optimal combination of tool specification and weld parameters that could consistently withstand high-speed production demands.

"What we discovered was a win-win," Hovanski said. "The faster the weld, the better the quality and strength of the join, thus the significant increase in speed."

PNNL provided the weld and tool specifications to TWB Company and GM. TWB Company then independently welded, formed and analyzed more than 100 aluminum blanks in close coordination with GM, making them the first qualified supplier of aluminum tailor-welded blanks. GM subsequently stamped their first full-sized inner door panel supplied by TWB Company -- free of imperfections -- from aluminum sheets in varying thicknesses.

Today, TWB Company has a dedicated FSW machine at their production facility in Monroe, MI, built around PNNL's process that is capable of producing up to 250,000 parts per year. "TWB can now provide aluminum tailor welds not only to GM, but the entire automotive industry," said Blair Carlson, a group manager at GM who con-conceptualized the project.

Next up

With over two years of funding left, the team continues to collaborate, with a focus on even faster weld speeds and the ability to maneuver around the contours and corners of complex aluminum parts, for which laser welding is not commercially feasible. The team also is modifying FSW to join different alloys, such as automotive-grade aluminum alloys with light, ultra-high strength alloys currently reserved for aerospace applications.

"Going forward, we see this process, and future versions of it, enabling completely novel combinations of materials that will revolutionize material use in the auto industry," Hovanski said.

Source: DOE/Pacific Northwest National Laboratory – 11.05.2015.

Reference:

Y. Hovanski, P. Upadhyay, J. Carsley, T. Luzanski, B. Carlson, M. Eisenmenger, A. Soulami, D. Marshall, B. Landino, S. Hartfield-Wunsch. High-speed friction-stir welding to enable aluminum tailor-welded blanks, JOM, April 2, 2015, DOI:10.1007/s11837-015-1384-x

Investigated and edited by:

Dr.-Ing. Christoph Konetschny, Inhaber und Gründer von Materialsgate
Büro für Material- und Technologieberatung
The investigation and editing of this document was performed with best care and attention.
For the accuracy, validity, availability and applicability of the given information, we take no liability.
Please discuss the suitability concerning your specific application with the experts of the named company or organization.

You want additional material or technology investigations concerning this subject?

Materialsgate is leading in material consulting and material investigation.
Feel free to use our established consulting services

MMore on this topic

Evonik Corporation, Parsippany, USA, was recently named by U.S. President Barack Obama as a key partner of the Advanced Composites Manufacturing Innovation Institute (IACMI), a $250 million public-private partnership of academia, federal and state government, and companies seeking to advance the commercialization of novel material sciences and composites solutions to the automotive, wind energy and compressed natural gas tank industries.

Led by the University of Tennessee at Knoxville, the IACMI reflects a $70 million commitment from the U.S. Department of Energy and $189 million from IACMI’s partners. IACMI is the fifth named institute of President Obama’s National Network for Manufacturing Innovation. “Evonik is proud and excited to have an opportunity to work with technology leaders across academia and industry to bring composite solutions to life,” said Dr. Matthias Kottenhahn, head of Evonik High Performance Polymers business line. “Evonik’s participation in IACMI is right in our sweet spot, as we have a strategy of offering the world commercially viable ideas on how to utilize resources more efficiently... more read more

Tough, ultralight foam of atom-thick sheets can be made to any size and shape through a chemical process invented at Rice University.

In microscopic images, the foam dubbed “GO-0.5BN” looks like a nanoscale building, with floors and walls that reinforce each other. The structure consists of a pair of two-dimensional materials: floors and walls of graphene oxide that self-assemble with the assistance of hexagonal boron nitride platelets. The researchers say the foam could find use in structural components, as supercapacitor and battery electrodes and for gas absorption, among other applications. The research by an international collaboration led by the Rice lab of materials scientist Pulickel Ajayan is detailed today in the online journal Nature Communications. Graphene oxide (GO) is a variant of graphene, the hexagonal... more read more

Imagine a material with the same weight and density as aerogel -- a material so light it's called 'frozen smoke' -- but with 10,000 times more stiffness. This material could have a profound impact on the aerospace and automotive industries as well as other applications where lightweight, high-stiffness and high-strength materials are needed.

Lawrence Livermore National Laboratory (LLNL) and Massachusetts Institute of Technology (MIT) researchers have developed a material with these properties using additive micro-manufacturing processes. The research team's findings are published in a June 20 article in the journal Science. Titled "Ultralight, Ultrastiff Mechanical Metamaterials," the article describes the team's development of micro-architected metamaterials -- artificial materials with properties not found in nature -- that maintain a nearly constant stiffness per unit mass density, even at ultralow density. Materials with these properties could someday be used to develop parts and components for aircraft... more read more

MaterialsgateNEWSLETTER

Partner of the Week

Search in MaterialsgateNEWS

MaterialsgateFAIR:
LET YOURSELF BE INSPIRED