TY - JOUR
T1 - High strength and superconductivity in nanostructured niobium-titanium alloy by high-pressure torsion and annealing
T2 - Significance of elemental decomposition and supersaturation
AU - Edalati, Kaveh
AU - Daio, Takeshi
AU - Lee, Seungwon
AU - Horita, Zenji
AU - Nishizaki, Terukazu
AU - Akune, Tadahiro
AU - Nojima, Tsutomu
AU - Sasaki, Takahiko
N1 - Funding Information:
K.E. thanks the Japan Society for Promotion of Science (JSPS) for a Grant-in-Aid for Research Activity (No. 25889043 ). This work was supported in part by the Light Metals Educational Foundation of Japan and in part by a Grant-in-Aid for Scientific Research from the MEXT, Japan , in Innovative Areas “Bulk Nanostructured Metals” (No. 22102004 ).
PY - 2014/11
Y1 - 2014/11
N2 - A powder mixture of Nb-47 wt.% Ti (a well-known composition for superconducting magnets) was subjected to severe plastic deformation using high-pressure torsion (HPT) and subsequently annealed at 573 K. Ti gradually dissolved in Nb with increasing shear strain, with a fast kinetics comparable to lattice diffusion at 700-1200 K. At large strains, a complete transition to a nanostructured β phase occurred at room temperature, which is far below the equilibrium temperature of 690 K. Nanoclusters of Ti with a body-centered cubic structure were also detected at large strains. Subsequent annealing led to elemental decomposition, formation of a nanoscale lamellar structure and segregation of Nb at grain boundaries. Superconductivity occurred at temperatures below 9 K, while the transition temperature decreased with increasing shear strain because of supersaturation of Ti in Nb and increased with annealing because of elemental decomposition. The Nb-Ti alloy after HPT exhibited hardness/strength peaks followed by softening at large strains, while hardening occurred after annealing. The maximum hardness, tensile and bending strengths were 4, 1.7 and 2.7 GPa, respectively.
AB - A powder mixture of Nb-47 wt.% Ti (a well-known composition for superconducting magnets) was subjected to severe plastic deformation using high-pressure torsion (HPT) and subsequently annealed at 573 K. Ti gradually dissolved in Nb with increasing shear strain, with a fast kinetics comparable to lattice diffusion at 700-1200 K. At large strains, a complete transition to a nanostructured β phase occurred at room temperature, which is far below the equilibrium temperature of 690 K. Nanoclusters of Ti with a body-centered cubic structure were also detected at large strains. Subsequent annealing led to elemental decomposition, formation of a nanoscale lamellar structure and segregation of Nb at grain boundaries. Superconductivity occurred at temperatures below 9 K, while the transition temperature decreased with increasing shear strain because of supersaturation of Ti in Nb and increased with annealing because of elemental decomposition. The Nb-Ti alloy after HPT exhibited hardness/strength peaks followed by softening at large strains, while hardening occurred after annealing. The maximum hardness, tensile and bending strengths were 4, 1.7 and 2.7 GPa, respectively.
KW - Critical temperature of superconductivity
KW - Electrical properties
KW - Magnetic properties
KW - Severe plastic deformation (SPD)
KW - Ultrafine-grained (UFG) materials
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U2 - 10.1016/j.actamat.2014.07.065
DO - 10.1016/j.actamat.2014.07.065
M3 - Article
AN - SCOPUS:84906712551
SN - 1359-6454
VL - 80
SP - 149
EP - 158
JO - Acta Materialia
JF - Acta Materialia
ER -