電解コンデンサ用高純度アルミニウム箔における粗大結晶粒発生に及ぼす不純物水素の影響 Influence of impurity hydrogen on coarse grain evolution in high purity aluminum foils for electrolytic capacitors
Two aluminum plates with 99.99 mass% purity with different hydrogen contents of 0.17 and 0.41 mass ppm were hot-rolled to 10 mm in thickness, cold-rolled by 99% to 130 μm in thickness, annealed at 250°C for 2 h, cold-rolled by 15% to 110 μm in thickness and finally annealed, which is similar to commercial processes of high purity aluminum foils for electrolytic capacitors. The foils were subjected to optical macro- and micro-scopies, thermal desorption spectroscopy (TDS), hydrogen micro-print technique (HMPT) and electron back-scattering diffraction pattern (EBSP) analysis and the effect of impurity hydrogen on the growth of off-cube grains in a recrystallized microstructure with a strong cube texture was investigated. It was confirmed that abnormal grain growth of off-cube grains becomes more conspicuous with the increase in the amount of impurity hydrogen in the original ingot. The HMPT analysis showed that hydrogen concentration in the cube-oriented region was larger than in the off-cube grain. The grain size in the cube-oriented region decreased with decreasing hydrogen content. From these facts and the result of TDS, supersaturated hydrogen atoms were presumed to segregate to low angle grain boundaries, the boundaries between cube-oriented grains, which can provide the driving force for the abnormal grain growth.
軽金属 58(6), 229-235, 2008-06-30
The Japan Institute of Light Metals