Scientists at the Lawrence Berkeley National Laboratory (Berkeley Lab) and collaborators have made a groundbreaking discovery by creating an alloy that challenges the conventional understanding of metal strength and resilience. This newly engineered material, comprising a mix of niobium, tantalum, titanium, and hafnium, defies the norm by resisting cracks and maintaining its toughness across an extensive temperature spectrum, from the chilly -196°C to a scorching 1200°C.
The research, conducted by a team led by Robert Ritchie at Berkeley Lab and UC Berkeley, alongside professors Diran Apelian at UC Irvine and Enrique Lavernia at Texas A&M University, was published in Science on April 11, 2024. This innovation could herald a new era for next-generation engines and aerospace components, as it promises higher efficiencies at temperatures that would cause conventional metals to succumb to kinking or bending at the atomic level.
Unlike typical alloys, which consist of one primary metal mixed with smaller amounts of other elements, this refractory high or medium entropy alloy (RHEA/RMEA) mixes near-equal proportions of metals with very high melting temperatures, bestowing upon it uncommon properties that scientists are diligently working to understand.
Previously, RHEAs/RMEAs were known to be strong but exhibited extremely low fracture toughness, making them brittle and prone to snapping under stress. The novel Nb45Ta25Ti15Hf15 RMEA alloy, however, has shown to be “exceptionally high in toughness,” outperforming even cryogenic steel at room temperature.
David Cook, a Ph.D. student in Ritchie’s lab, remarked, “The efficiency of converting heat to electricity or thrust is determined by the temperature at which fuel is burned – the hotter, the better.” This new alloy can operate at temperatures previously deemed too extreme, and thus it has exhausted the ability to optimize current materials at high temperatures, signaling the need for innovative metallic materials.
The team was particularly surprised by a phenomenon known as ‘kink bands,’ a type of defect that was historically thought to weaken the metal by making it easier for cracks to spread. Counterintuitively, they found that kink bands actually enhance the alloy’s toughness by distributing damage away from the crack, acting as a barrier to fracture and consequently leading to “extraordinarily high fracture toughness.”
The research incorporated advanced techniques such as four-dimensional scanning transmission electron microscopy (4D-STEM) and scanning transmission electron microscopy (STEM) to delve into the atomic structure of the alloy and unlock the secrets behind its unprecedented performance.
Despite the excitement surrounding the alloy, Ritchie emphasized that substantial research and testing are still needed before practical applications can be realized. Engineers require a deep understanding of a material’s performance before incorporating it into real-world applications.
The Lawrence Berkeley National Laboratory, renowned for excellence and its history of Nobel prize-winning work, was instrumental in this scientific advancement. With a legacy of fostering collaborative research, the lab continues to contribute to solving some of the most pressing scientific challenges of the time.
Relevant articles:
– This alloy is kinky: It just won’t crack or bend at extreme temperatures, India Today
– Samueli School of Engineering at UC Irvine, University of California, Irvine
– From The DOE’s Lawrence Berkeley National Laboratory: “This Alloy is Kinky”, sciencesprings
– Research UC Berkeley, University of California, Berkeley