Scientists at Purdue University say they have developed a new aluminium alloy with strength comparable to stainless steel.
According to researchers at the university’s School of Materials Engineering, altering the metal’s crystal lattice by introducing distortions known as “stacking faults,” or omitting a layer in the crystal’s atomic structure, can add strength to the metal that it would not have ordinarily possessed. Two stacking faults, known as “twin boundaries,” are capable of enhancing the alloy’s strength even more.
Purdue professor Xinghang Zhang says that a particular stacking fault, referred to as 9R, holds special promise for strengthening aluminium.
“It has been shown that twin boundaries are difficult to be introduced into aluminum. The formation of the 9R phase in aluminum is even more difficult because of its high stacking fault energy. You want to introduce both nanotwins and 9R phase in nanograined aluminum to increase strength and ductility and improve thermal stability.
“These results show how to fabricate aluminum alloys that are comparable to, or even stronger than, stainless steels. There is a lot of potential commercial impact in this finding.”
Purdue research associate Sichuang Xue explains that, by bombarding ultrathin aluminum films with tiny micro-projectiles of silicon dioxide (SiO2), researchers were able to produce the 9R phase.
“Here, by using a laser-induced projectile impact testing technique, we discover a deformation-induced 9R phase with tens of nanometers in width.”
A second team of researchers at Rice University carried out a test utilizing laser beams to shoot silicon dioxide particles at 600 meters per second (1,342 mph) into the aluminium films, which significantly shortened screening tests of alloys for impact resistance.
Zhang says the aluminium alloy they developed is among the strongest varieties of aluminium known to man.
“Molecular-dynamics simulations, performed by professor Jian Wang’s group at the University of Nebraska, Lincoln, showed the 9R phase and nanograins result in high strength and work-hardening ability and revealed the formation mechanisms of the 9R phase in aluminum. Understand[ing] new deformation mechanisms will help us design new high strength, ductile metallic materials, such as aluminum alloys.”
Such a breakthrough could portend great things for manufacturers in fields that require high-strength, lightweight metals, opines Zhang.
“Most lightweight aluminum alloys are soft and have inherently low mechanical strength, which hinders more widespread industrial application. However, high-strength, lightweight aluminum alloys with strength comparable to stainless steels would revolutionize the automobile and aerospace industries.”
The team’s findings were published earlier this month in the journal Advanced Materials. A previous paper written by the team was published late last year in Nature Communications.