The research team led by Professor Chain Tsuan LIU has worked out a novel strategy for developing new super alloys that are extremely strong yet ductile and flexible. The breakthrough solution addresses a daunting, decades-long dilemma in materials science. The new alloys were developed based on multiple-principal-element alloys, which are also referred to as high-entropy alloys (HEAs). These are new materials constructed with equiatomic or nearly equiatomic percentages of five or more elements. Most conventional alloys are made of one or two major elements, such as nickel and iron. The team found that adding aluminum and titanium to form massive complex nanoparticles resulted in a significant increase in both the strength and ductility of the alloys. Previously, the stronger an alloy was, the less ductile and tough it was, meaning stronger alloys tended to fracture when deformed or stretched. This new alloy is five times stronger than iron-cobalt-nickel based alloys and is 1.5 times more ductile. The cutting-edge research was published in the latest issue of the prestigious journal Science, in an article titled “Multicomponent intermetallic nanoparticles and superb mechanical behaviours of complex alloys” [2].
The deformation of high-strength alloys can easily cause necking fracture (localized deformation), but the research team found that adding complex nanoparticles consisting of nickel, cobalt, iron, titanium, and aluminium atoms enables extended uniform deformation. Replacing some of the nickel components with iron and cobalt atoms helped to improve the ductility of the new alloy, and replacing some of the aluminium with titanium helped to reduce the embrittlement effect caused by ambient moisture in the air.
The research team believed the new alloy developed with this novel strategy would perform well in temperatures ranging from -200°C to 1000°C, thus providing a good base for developing new cryogenic devices, as well as aircraft and high-temperature systems, such as aeronautical engineering applications.
The new high-entropy alloy is extremely strong, yet ductile and flexible [2].
Reference
1. Yang, T, Zhao, YL, Li, WP, Yu, CY, Luan, JH, Lin, DY, Fan, L, Jiao, ZB, Liu, WH, Liu, XJ, Kai, JJ, Huang, JC & Liu, CT 2020, 'Ultrahigh-strength and ductile superlattice alloys with nanoscale disordered interfaces', Science (New York, N.Y.), vol. 369, no. 6502, pp. 427-432.
2. Yang, T, Zhao, YL, Tong, Y, Jiao, ZB, Wei, J, Cai, JX, Han, XD, Chen, D, Hu, A, Kai, JJ, Lu, K, Liu, Y & Liu, CT 2018, 'Multicomponent intermetallic nanoparticles and superb mechanical behaviors of complex alloys', Science (New York, N.Y.), vol. 362, no. 6417, pp. 933-937.
3. Zhang, T, Huang, Z, Yang, T, Kong, H, Luan, J, Wang, A, Wang, D, Kuo, W, Wang, Y & Liu, C-T 2021, 'In situ design of advanced titanium alloy with concentration modulations by additive manufacturing', Science, vol. 374, no. 6566, pp. 478-482.