کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
5435770 | 1509536 | 2017 | 7 صفحه PDF | دانلود رایگان |
High pressure torsion (HPT) experiments have been carried out at very low temperatures (â78 °C) on dilute Cu-Nb alloys. The samples were prepared by magnetron sputtering to create solid solutions containing nominally between 1 at.% and 10 at.% Nb. Some samples were pre-annealed to 700 °C to form large Nb precipitates, â¼75 nm in radius, prior to HPT. For the unannealed alloys, HPT at low temperatures led to alloy decomposition for alloys with concentrations greater than â¼2 at.% Nb, with the steady state concentration of Nb increasing from â¼1.5 to â¼3 at.% as the initial concentration of Nb was increased. It was also observed that BCC Nb precipitates formed during low-temperature HPT, with a steady state precipitate size â¼10 nm in radius, which was insensitive to alloy concentration. HPT of pre-annealed Cu-10 at.% alloy led to the same steady state microstructure as the unannealed sample, indicating that the steady state during the low temperature HPT process is independent of the initial state for these Cu-Nb alloys. A model for phase evolution in strongly immiscible alloys during severe, low-temperature deformation is offered and implemented through kinetic Monte Carlo simulations. Good agreement with experiment is obtained.
The solubility vs strain of niobium in copper and the size distribution of niobium precipitates found after a strain of â¼2000. It can be seen that HPT of pre-annealed Cu- 10 at.% alloy led to the same steady state microstructure and solubility as the unannealed sample, indicating the low temperature HPT process is ergodic for these Cu-Nb alloys.438
Journal: Acta Materialia - Volume 140, November 2017, Pages 217-223