Researchers from North Carolina State University (NC State) and Qatar University have developed a new metal alloy that has a higher strength-to-weight ratio than any other existing metallic material.
This new alloy is ‘high-entropy’, this type of alloy consists of five or more metals in approximately equal amounts. These alloys are currently the focus of significant attention in materials science and engineering because they can have desirable properties.
The NC State research team combined lithium, magnesium, titanium, aluminium and scandium to make a nanocrystalline high-entropy alloy that has low density, but very high strength.
The senior author of the paper on this research, Dr Carl Koch, Kobe Steel Distinguished Professor of Materials Science and Engineering at NC State, describes the alloy as having a density comparable to aluminium but with the strength of titanium. This combination is apparently unmatched by other metallic materials with the nearest comparison being with ceramic materials, which also suffer from brittleness.
There are a wide range of uses for strong, lightweight materials, such as in vehicles or prosthetic devices. As this alloy is in a early phase of research there is much more work to do to categorise and investigate the best ways to process the metal into useful components.
One of the main problems with the alloy at the moment is that it is made of 20 percent scandium, which is extremely expensive. The researchers are looking into ways to substitute the scandium for a less expensive alternative, while maintaining the same properties.
The paper “A Novel Low Density, High Hardness, High-Entropy Alloy with Close-packed Single-phase Nanocrystalline Structures,” is published online in the open-access journal Materials Research Letters. Lead author of the paper is Dr. Khaled Youssef of Qatar University. Co-authors include Alexander Zaddach and Changning Niu, Ph.D. students at NC State; and Douglas Irving, an associate professor of material science and engineering at NC State.
Article adapted from NC State News- 10th December 2014