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Yoshikazu Todaka

Affiliation Department of Mechanical Engineering
Title Professor
Fields of Research Physical Metallurgy
Degree Dr. Eng. (Toyohashi Univ. of Technology)
Academic Societies The Japan Institute of Metals / The Iron and Steel Institute of Japan / The Minerals, Metals & Materials Society / The Japan Institute of Light Metals / The Thermoelectrics Society of Japan / The Japan Society of Mechanical Engineers / The Society of Mate
E-mail todaka@me
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In order to high-functionalization (of mechanical property) in metals beyond conventional knowledge, we perform multi-scale control of microstructure by severe plastic deformation.

Theme1:High-functionalization of metals by severe plastic deformation

Tensile property of bulk submicrocrystalline pure Fe produced by HPT-straining. HPT-processed specimens have high tensile strength and large elongation.

In recent years, with the appearance of nano / submicro - crystalline (NC/SC) metals and alloys prepared by severe plastic deformation, new ways to improve mechanical properties of materials have been developed. We prepare “BULK” NC/SC materials by high-pressure torsion and “SURFACE” NC/SC materials by surface - nanocrystallized wearing. We create materials with new characteristics including mechanical properties beyond conventional knowledge by severe plastic deformation.

Selected publications and works

[1] Y. Todaka et al.; Tensile property of submicrocrystalline pure Fe produced by HPT-straining; Materials Science Forum, vol.584-586 (2008) pp.597-602.
[2] Y. Todaka et al.; Hydrogen embrittlement of submicrocrystalline ultra-low carbon steel produced by high-pressure torsion straining; Advanced Materials Research, vol.89‐91 (2010) pp.763‐768.
[3] Y. Todaka et al.; Bulk submicrocrystalline ω-Ti produced by high-pressure torsion straining; Scripta Materialia, vol.59 (2008) pp.615-618.
[4] N. Adachi, N. Wu, Y. Todaka et al.; Phase transformation in Fe-Mn-C alloys by severe plastic deformation under high pressure; Materials Letters, vol.185 (2016) pp.109-111.
[5] Y. Todaka et al.; Formation of ultrafine-grained structure at drill-hole surface of martensitic steels by high-speed drilling and their mechanical properties; Tetsu-to-Hagane, vol.96 (2010) pp.21-28.
[6] Y. Todaka et al.; Effect of lattice defects on tribological behavior for low friction coefficient under lubricant in nanostructured steels; Tetsu-to-Hagane, vol.101 (2015) pp.530-535.
[7] N. Adachi, Y. Todaka et al.: Improving the mechanical properties of Zr-based bulk metallic glass by controlling the activation energy for β-relaxation through plastic; Applied Physics Letters, vol.105 (2014) pp.131910 1-5.


Lattice defect, Grain refinement, Phase transformation, Plastic deformation

Theme2:Development of Low Environmentally Hazardous Thermoelectric Materials


Thermoelectric effect, discovered in 1823 by Seebeck, is finding more applications than ubiquitous thermocouples. Electric power can be extract from waste heat by the thermoelectric effect. We have been focusing on the development of metallic silicide thermoelectric materials which consist of non-toxic and abundant materials. By controlling of microstructure with appropriate doping, it is possible to maximize the efficiency of power generation.

Selected publications and works

[1] Y. Niwa, Y. Todaka et al.; Thermoelectric Property of Na-doped Mg2Si; J. Japan Inst. Metals, vol.72 (2008) pp.693-697.
[2] Y. Niwa, Y. Todaka et al.; Thermoelectric properties of Ca-Mg-Si alloys; Materials Transactions, vol.50 (2009) pp.1725-1729.
[3] N. Miyazaki, N. Adachi, Y. Todaka et al.; Thermoelectric property of bulk CaMgSi intermetallic compound; Journal of Alloys and Compounds, vol.691 (2017) pp.914‐918.


Thermoelectric effect, Low environmentally hazardous material, Waste heat

Title of class

Introduction of Mechanical Engineering (B11510090) / Introduction to Materials Engineering (B11530190) / Research Project (B11510080) / Statistical Analysis (B11610160) / Materials and Processing in Mechanical Engineering (B11630070) / Experimental Practice for Mechanical Engineering (B11610021, B11610023) / Structural Materials (B11622060) / Advanced Materials Function Control Engineering (M21622130) / Advanced Materials Science (D31030040)

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