TY - JOUR

T1 - Deformation-driven formation of equilibrium phases in the Cu-Ni alloys

AU - Straumal, B. B.

AU - Protasova, S. G.

AU - Mazilkin, A. A.

AU - Rabkin, E.

AU - Goll, D.

AU - Schütz, G.

AU - Baretzky, B.

AU - Valiev, R. Z.

PY - 2012/1/1

Y1 - 2012/1/1

N2 - The homogeneous coarse-grained (CG) Cu-Ni alloys with nickel concentrations of 9, 26, 42, and 77 wt% were produced from as-cast ingots by homogenization at 850 °C followed by quenching. The subsequent high-pressure torsion (5 torsions at 5 GPa) leads to the grain refinement (grain size about 100 nm) and to the decomposition of the supersaturated solid solution in the alloys containing 42 and 77 wt% Ni. The lattice spacing of the fine Cu-rich regions in the Cu-77 wt% Ni alloy was measured by the X-ray diffraction (XRD). They contain 28 ± 5 wt% Ni. The amount of the fine Ni-rich ferromagnetic regions in the paramagnetic Cu-42 wt% Ni alloy was estimated by comparing its magnetization with that of fully ferromagnetic Cu-77 wt% Ni alloy. According to the lever rule, these Ni-rich ferromagnetic regions contain about 88 wt% Ni. It means that the high-pressure torsion of the supersaturated Cu-Ni solid solutions produces phases which correspond to the equilibrium solubility limit at 200 ± 40 °C (Cu-77 wt% Ni alloy) and 270 ± 20 °C (Cu-42 wt% Ni alloy). To explain this phenomenon, the concept of the effective temperature proposed by Martin (Phys Rev B 30:1424, 1984) for the irradiation-driven decomposition of supersaturated solid solutions was employed. It follows from this concept that the deformation-driven decomposition of supersaturated Cu-Ni solid solutions proceeds at the mean effective temperature T eff = 235 ± 30 °C. The elevated effective temperature for the high-pressure torsion-driven decomposition of a supersaturated solid solution has been observed for the first time. Previously, only the T eff equal to the room temperature was observed in the Al-Zn alloys.

AB - The homogeneous coarse-grained (CG) Cu-Ni alloys with nickel concentrations of 9, 26, 42, and 77 wt% were produced from as-cast ingots by homogenization at 850 °C followed by quenching. The subsequent high-pressure torsion (5 torsions at 5 GPa) leads to the grain refinement (grain size about 100 nm) and to the decomposition of the supersaturated solid solution in the alloys containing 42 and 77 wt% Ni. The lattice spacing of the fine Cu-rich regions in the Cu-77 wt% Ni alloy was measured by the X-ray diffraction (XRD). They contain 28 ± 5 wt% Ni. The amount of the fine Ni-rich ferromagnetic regions in the paramagnetic Cu-42 wt% Ni alloy was estimated by comparing its magnetization with that of fully ferromagnetic Cu-77 wt% Ni alloy. According to the lever rule, these Ni-rich ferromagnetic regions contain about 88 wt% Ni. It means that the high-pressure torsion of the supersaturated Cu-Ni solid solutions produces phases which correspond to the equilibrium solubility limit at 200 ± 40 °C (Cu-77 wt% Ni alloy) and 270 ± 20 °C (Cu-42 wt% Ni alloy). To explain this phenomenon, the concept of the effective temperature proposed by Martin (Phys Rev B 30:1424, 1984) for the irradiation-driven decomposition of supersaturated solid solutions was employed. It follows from this concept that the deformation-driven decomposition of supersaturated Cu-Ni solid solutions proceeds at the mean effective temperature T eff = 235 ± 30 °C. The elevated effective temperature for the high-pressure torsion-driven decomposition of a supersaturated solid solution has been observed for the first time. Previously, only the T eff equal to the room temperature was observed in the Al-Zn alloys.

UR - http://www.scopus.com/inward/record.url?scp=84855548225&partnerID=8YFLogxK

U2 - 10.1007/s10853-011-5805-0

DO - 10.1007/s10853-011-5805-0

M3 - Article

AN - SCOPUS:84855548225

VL - 47

SP - 360

EP - 367

JO - Journal of Materials Science

JF - Journal of Materials Science

SN - 0022-2461

IS - 1

ER -