High strength oxide dispersion strengthened silver aluminum alloys optimized for Bi_2Sr_2CaCu_2O_(8+x) round wire

摘要

High strength dispersion strengthened (DS) Ag/Al alloys with various Al content are studied as candidates for sheathing Bi_2Sr_2CaCu_2O_(8+x) (Bi2212) wire. The Ag/Al alloys are fabricated by powder metallurgy and internally oxidized in pure oxygen. The time and temperature of the internal oxidation heat treatment is varied to maximize the strength after undergoing the Bi2212 partial melt process (PMP). Vickers micro-hardness number (HVN), room temperature tensile behavior, optical and scanning electron microscopy, ion channeling contrast imaging using a focused ion beam and electrical resistivity measurements are used to characterize the alloys. An Ag/0.2wt%Mg (Ag/Mg) alloy is used for comparison. Results show that internal oxidation at 650-700 ℃ for 4 h produces the highest HVN for the DS Ag/Al alloy; when oxidized at 675 ℃ for 4 h the HVN, yield strength and tensile strength of the DS Ag/Al are 50% higher than the corresponding values of Ag/Mg. Microstructural observations show that Al_2O_3 precipitates play the main role in strengthening the DS Ag/Al alloy. The alloy retains its fine grain structure and strength after PMP heat treatment.