Metals usually exist in form of polycrystalline solids, in which the networks of disordered grain boundaries tend to get eliminated through grain coarsening upon heating or straining, or to transform into metastable amorphous states when the grains are small enough. This is why nano-grained structures in metals are much more unstable relative to their coarse-grained counterparts. Through experiments and molecular dynamic simulations, we recently discovered a novel metastable structure in metals with grains of few nanometers in size, namely Schwarz crystal structure. The GB-network of the metal is characterized by 3D minimal interfaces structure with a zero-mean-curvature constrained by twin boundaries. The unique structure is thermally stable against grain coarsening at temperatures close to the equilibrium melting point and exhibits a hardness in vicinity of the theoretical value. The across-boundary diffusion is so effectively suppressed that the diffusion-controlled processes such as intermetallic precipitation are inhibited. In this presentation, Professor Ke Lu will introduce the formation process, structure characteristics, and some properties of the Schwarz crystal structures in a number of pure metals and alloys.
Professor Ke Lu received BS in MSE from Nanjing University of Science & Technology in 1985 and PhD in MSE from Institute of Metal Research of Chinese Academy of Sciences in 1990. He is a professor and the founding director of Shenyang National Laboratory for Materials Science. His research interests are nanostructured metals and alloys. He authored and co-authored more than 400 publications and held 30 patents. He is a member of Chinese Academy of Sciences, German National Academy of Sciences Leopoldina, and the National Academy of Engineering of USA. He is a Fellow of the AAAS, MRS, and TMS.
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