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Topic: Schwarz crystal: the polycrystalline structure at extreme in metals

Speaker: Professor Ke Lu

Host: Professor Ben Zhong Tang

Date: Thursday, April 9, 2026

Time: 3:00 PM - 4:45 PM

Venue: SIN Wai Kin International Conference Centre (W201), Administration Building

Language: Chinese

Abstract: 

Metallic materials are usually in form of polycrystalline structures consisting of crystalline grains separated by grain boundaries (GBs) where atomic arrangement is disordered. GBs may resist dislocation slip, strengthening metals as expressed in the classical Hall-Petch relation. Metals’ strength may multiply as grains are refined into the nanometer scale. However, GBs are detrimental to many other properties such as ductility and stability because they are sources of other lattice defects and cracks, and mobile under thermal and mechanical activation. This is why we make single-crystal super alloys by eliminating GBs in the gas turbine plates for service under harsh conditions. 

Recently, Academician Ke Lu’s team discovered a novel metastable structure in polycrystalline face-centered-cubic metals with an extremely high density of GBs at grain sizes of few nanometers, namely Schwarz crystal. In this structure, GBs evolved into the 3D periodical minimal surface (TPMS) networks constrained with high density twin-boundaries. The structure is extremely robust even close to the melting point. Strength of the Schwarz crystal metal is near the theoretical value. In this presentation, he will introduce the formation process, structure characteristics, and some properties of the Schwarz crystal structures in a number of pure metals and alloys. Perspectives and future studies on the extreme polycrystalline structure will be discussed.  

Speaker Profile:

Ke Lu, Founding President of Liaoning Academy of Materials (LAM), Professor of Institute of Metal Research (CAS). His identity accomplishments include: (1) Discovered three novel nanostructures in metals: Schwarz crystal structure, nano-twinned structures, and sub-nanostructures with negative-energy-interfaces. (2) Revealed strengthening mechanisms of nano-twins and gradient nanostructures in metals. Developed a series of techniques for generating gradient nanostructured metals and alloys for advancing properties and performance. (3) Proposed a “Material planification” strategy for advancing material properties and performance by tailoring stable interfaces with minimized alloying elements. 

He received prestigious honors and awards, including TMS Robert Franklin Mehl Award (USA, 2022), Acta Materialia Gold Medal (2019), AvH Research Award (Germany, 2010), Kelly Lecturer (University of Cambridge, UK, 2010). He is a member of Chinese Academy of Sciences (2003), a foreign member of German National Academy Leopoldina (2005) and National Academy of Engineering of USA (2018).