Scripta Materialia 

Abstract: Phonon plays essential roles in dynamical behaviors and thermal properties, which are central topics in fundamental issues of materials science. The importance of first principles phonon calculations cannot be overly emphasized. Phonopy is an open source code for such calculations launched by the present authors, which has been world-widely used. Here we demonstrate phonon properties with fundamental equations and show examples how the phonon calculations are applied in materials science.

Abstract: Considerable interest has centered recently on the processing of materials with ultra-fine grain sizes, typically <100 nm. These materials may be prepared by various techniques including gas condensation and subsequent in situ consolidation under high vacuum, high energy ball milling and sliding wear. Alternatively, it has been shown that submicrometer-grained structures may be produced in a wide range of materials (e.g. pure metals, metallic alloys including superalloys, intermetallics, semiconductors) by subjecting these materials to a very high plastic strain using either equal-channel angular (ECA) pressing or torsion straining under high pressure. These latter procedures usually give grain sizes in the submicrometer range of {approximately}100--200 nm although there are reports of grain sizes as small as {approximately}50 nm. In practice, ECA pressing is an especially attractive processing method because it provides the capability of producing large bulk samples which are free from any residual porosity.

Abstract: The Hall–Petch relation is discussed separately for the yield stress of undeformed polycrystalline metals and for the flow stress of deformed metals. Key structural parameters are the boundary spacing, between grain boundaries in the former case and between dislocation boundaries and high angle boundaries in the latter. An analysis of experimental data supports the Hall–Petch relation for undeformed metals over a grain size range from about 20 nm to hundreds of micrometers. For deformed metals, boundary strengthening is not a constant and the Hall–Petch relation must be modified.

Abstract: The potential of metallic glasses as structural materials is assessed. A wide-ranging comparison with conventional engineering materials shows metallic glasses to be restricted to niche applications, but with outstanding properties awaiting wider application, for example in micro electro-mechanical systems devices.