TY - JOUR
T1 - Unusual hardening in Ti/Al2O3 nanocomposites produced by high-pressure torsion followed by annealing
AU - Edalati, Kaveh
AU - Iwaoka, Hideaki
AU - Horita, Zenji
AU - Konno, Mitsuru
AU - Sato, Takahiro
N1 - Funding Information:
We would like to thank Mr. Shingo Nishihata of Kyushu University for his kind assistance. One of the authors (KE) also thanks the Japan Society for Promotion of Science (JSPS) for a postdoctoral scholarship. This work was supported in part by the Light Metals Educational Foundation of Japan, in part by a Grant-in-Aid for Scientific Research from the Ministry of Education, Culture, Sports, Science and Technology of Japan in the Priority Area “Bulk Nanostructured Metals”, and in part by Kyushu University Interdisciplinary Programs in Education and Projects in Research Development (P&P).
PY - 2011/11/25
Y1 - 2011/11/25
N2 - Nanocomposites of Ti-18vol.% Al2O3 were fully consolidated by applying severe plastic deformation to powder mixtures using high-pressure torsion (HPT). The HPT-processed composites exhibited an unusual increase in the hardness from 350Hv to 650Hv when they were annealed at 973K for 1h. Microstructural observations including elemental mappings were conducted using scanning electron microscopy with an electron probe X-ray micro-analyzer and scanning transmission electron microscopy with an energy dispersive X-ray spectrometer. It was shown that the Al2O3 particles are fragmented and the grain size of the Ti matrix is reduced to the nanometer level (<100nm) after processing with HPT. Following the annealing, the fragmented Al2O3 particles with particle sizes less than ∼400nm are reduced to Al in the Ti matrix and the average grain size of Ti is coarsened to ∼500nm in conflicting with the hardness increase. The hardness increase after annealing is attributed to the dissolution of Al and O atoms in the Ti-matrix and the formation of reaction product, Ti3Al intermetallic, at the interface and improvement of mechanical connectivity. Enrichment of Al along grain boundaries confirmed that Al atoms diffuse fast through the grain boundaries and move towards the grain interior from the grain boundaries.
AB - Nanocomposites of Ti-18vol.% Al2O3 were fully consolidated by applying severe plastic deformation to powder mixtures using high-pressure torsion (HPT). The HPT-processed composites exhibited an unusual increase in the hardness from 350Hv to 650Hv when they were annealed at 973K for 1h. Microstructural observations including elemental mappings were conducted using scanning electron microscopy with an electron probe X-ray micro-analyzer and scanning transmission electron microscopy with an energy dispersive X-ray spectrometer. It was shown that the Al2O3 particles are fragmented and the grain size of the Ti matrix is reduced to the nanometer level (<100nm) after processing with HPT. Following the annealing, the fragmented Al2O3 particles with particle sizes less than ∼400nm are reduced to Al in the Ti matrix and the average grain size of Ti is coarsened to ∼500nm in conflicting with the hardness increase. The hardness increase after annealing is attributed to the dissolution of Al and O atoms in the Ti-matrix and the formation of reaction product, Ti3Al intermetallic, at the interface and improvement of mechanical connectivity. Enrichment of Al along grain boundaries confirmed that Al atoms diffuse fast through the grain boundaries and move towards the grain interior from the grain boundaries.
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U2 - 10.1016/j.msea.2011.09.056
DO - 10.1016/j.msea.2011.09.056
M3 - Article
AN - SCOPUS:80054062573
SN - 0921-5093
VL - 529
SP - 435
EP - 441
JO - Materials Science & Engineering A: Structural Materials: Properties, Microstructure and Processing
JF - Materials Science & Engineering A: Structural Materials: Properties, Microstructure and Processing
IS - 1
ER -