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Highlight Lecture

WEB Synergy Effects and Unique Mechanical Properties of Harmonic Structure Materials

Wednesday (23.09.2020)
09:00 - 09:15 S: Structural Materials 2
Part of:

Metallic materials that combine high strength with high ductility are desired for many structural applications. Therefore, grain refinement is a well-known and attractive method to improve the strength of metallic materials. However, homogeneous and UFG materials are characterized by poor ductility. This effect, known as the strength-ductility trade-off, makes achieving good combinations of high strength and ductility rather challenging for the conventional homogeneous structural materials. A peculiar approach, to achieve a good combination of high strength without compromising in ductility, is a controlled and specific topological distribution of fine and coarse grains in the microstructure matrix, also called “Harmonic Structure (HS)”. As opposed to a homogeneous-UFG material, “HS” material has a unique heterogeneous “Three-dimensionally (3D) Gradient Microstructure” wherein the UFG areas form an interconnected three-dimensional network surrounding coarse grain (CG) regions. In addition, those CG and UFG areas are periodically arranged in all the directions. Such a novel microstructure can be induced in metals and alloys through controlled mechanical milling of metallic powder particles, followed by their sintering processes. The HS materials demonstrate various anomalous deformation behaviors, such as “synergy extra hardening”, “preferential recrystallization” and “preferential stress induced transformation”, and so on. It is concluded that those unique phenomena and mechanical properties are due to the synergy effects raised from Nano-scale and Macro-scale structures in the HS materials.

Prof. Kei Ameyama
Ritsumeikan University