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Volume 5, Issue 5
Res. Rev. J Mat. Sci. 2017
ISSN: 2321-6212
Advanced Materials 2017
September 07-08, 2017
September 07-08, 2017 | Edinburgh, Scotland
Advanced materials & Processing
11
th
International Conference on
Three-Dimensionally gradient harmonic structure design for high performance structural materials
Kei Ameyama
Ritsumeikan University, Japan
T
he Harmonic Structure (HS) is an innovative nano-micro scale materials design, which gives outstanding mechanical properties
to structural metallic materials. In general, homogeneous and ultra-fine grain (UFG) structure enables the materials high strength.
However, such a “Homo“ and “UFG” does not, usually, satisfy the need to be both strong and ductile, due to the plastic instability in
the early stage of the deformation. As opposed to such a “Homo and UFG“, “HS” has a heterogeneous microstructure consisting of
bimodal grain size together with a controlled and specific topological distribution of fine and coarse grains. In other words, the HS
is heterogeneous on nano- and micro- but homogeneous on macro-scales. In the present work, the HS design has been applied to
pure metals and alloys via a powder metallurgy route consisting of controlled surface severe plastic deformation of the corresponding
powders, and subsequent consolidation. At a macro-scale, the HS materials exhibited superior combination of strength and ductility
as compared to their homogeneous microstructure counterparts. Fig.1 demonstrates the comparison of mechanical properties of
various metals and alloys with HS and their coarse-grained (CG) counterparts. It can be clearly noted that the normalized yield
strength of the HS metals and alloys was considerably higher as compared to their CG counterparts. Since the area under the stress-
strain curve is considered as a representation of the toughness of a material, the HS materials also exhibited improved toughness.
These results clearly demonstrate that the HS design leads to improved mechanical properties in most of the metals and alloys which
indicate that the HS metallic material would also result in improved performance in service. This behavior was essentially related
to the ability of the HS to promote the uniform distribution of strain during plastic deformation, leading to improved mechanical
properties by avoiding or delaying localized plastic instability.
ameyama@se.ritsumei.ac.jpRes. Rev. J Mat. Sci. 2017, 5:5
DOI: 10.4172/2321-6212-C1-006