US and Chinese universities have demonstrated how to create a super-strong aluminium alloy that rivals the strength of stainless steel.
“Most lightweight aluminium alloys are soft and have inherently low mechanical strength, which hinders more widespread industrial application,” said Xinghang Zhang, a professor in Purdue University’s School of Materials Engineering.
“However, high-strength, lightweight aluminium alloys with strength comparable to stainless steels would revolutionise the automobile and aerospace industries.”
Naturally, such alloys might also prove useful in the cycle industry.
The research in how to alter the microstructure of aluminium to impart greater strength and ductility was led by a team of researchers that included Purdue postdoctoral research associate Sichuang Xue and doctoral student Qiang Li. Their work was published online in January in the journal Advanced Materials.
The new high-strength aluminium is made possible by introducing “stacking faults,” or distortions in the crystal structure. While these are easy to produce in metals such as copper and silver, they are difficult to introduce in aluminum because of its high “stacking fault energy.”
A metal’s crystal lattice is made up of a repeating sequence of atomic layers. If one layer is missing, there is said to be a stacking fault. Meanwhile, so-called “twin boundaries” consisting of two layers of stacking faults can form. One type of stacking fault, called a 9R phase, is particularly promising, Zhang said.
“It has been shown that twin boundaries are difficult to be introduced into aluminium. The formation of the 9R phase in aluminum is even more difficult because of its high stacking fault energy,” Zhang said. “You want to introduce both nanotwins and 9R phase in nanograined aluminum to increase strength and ductility and improve thermal stability.”
The research teams have now learned how to readily achieve this 9R phase and nanotwins.
“These results show how to fabricate aluminium alloys that are comparable to, or even stronger than, stainless steels,” said Zhang.
“There is a lot of potential commercial impact in this finding.”
The research was mainly funded by US Department of Energy’s Office of Basic Energy Sciences. The researchers have filed a patent application through the Purdue Research Foundation’s Office of Technology Commercialization. The team also included researchers from Purdue’s School of Materials Engineering, Department of Materials Science and NanoEngineering at Rice University, the Department of Engineering Physics at the University of Wisconsin-Madison, State Key Lab of Metal Matrix Composites, the School of Materials Science and Engineering at Shanghai Jiao Tong University, Department of Materials Science and Engineering at China University of Petroleum, California Institute of Technology, Louisiana State University and the University of Nebraska-Lincoln.