Alloys that have high strengths at high temperatures are crucial for a variety of important industries including aerospace. Long-range ordered superlattice alloys with strong chemical binding and associated low atomic mobility are attractive for this purpose. However, most conventional ordered alloys with ultrahigh strengths (gigapascal levels) are found to be extremely brittle during tensile deformation, which severely limits their potential use in structural applications.

A recent paper on a new class of high-strength and ductile superlattice alloys, co-authored by Mr Lei Fan, PhD student, and Dr Zengbao Jiao, Assistant Professor of the PolyU Department of Mechanical Engineering, was recently published in Science. In collaboration with Prof. CT Liu from the CityU and other colleagues, the researchers designed nanoscale disordered interfaces from the multi-element co-segregation, which act as a sustainable ductilizing source and prevent brittle intergranular fractures by enhancing dislocation mobilities. The newly developed multicomponent superlattice materials exhibit ultrahigh strengths of 1.6 gigapascals with tensile ductilities of 25% at ambient temperature. Moreover, these materials achieve negligible grain coarsening with exceptional softening resistance at elevated temperatures, demonstrating high thermal stability. These superlattice materials will be of great interest for a broad range of aerospace, automotive, nuclear power, chemical engineering, and other applications. In addition, the fundamental strategy of composite architecture can be utilized to design high-strength, ductile and stable materials in many other metallic systems.

Read more at: T. Yang, Y.L. Zhao, W.P. Li, C.Y. Yu, J.H. Luan, D.Y. Lin, L. Fan, Z.B. Jiao, W.H. Liu, X.J. Liu, J.J. Kai, J.C. Huang, C.T. Liu. Ultrahigh-strength and ductile superlattice alloys with nanoscale disordered interfaces. Science, 2020; 369 (6502): 427.