最大で2．2GPaの引張強度を持つCu-Zr合金線材の開発とそのミクロ組織

摘要

Round bar ingots of hypoeutectic Cu-4 and -5 at% Zr alloys cast into copper mold were wire-drawn (WD) with drawing ratio η= 5.9 and more, and the relationship between the mechanical and electrical properties and microstructures of those wires was investigated. As a result, it became obvious that the WD Cu-5 at% Zr alloy with η = 8.6, which was 40 |im in diameter, reached 2234 Mpa of ultimate tensile strength (UTS), 1873 Mpa of 0.2% proof stress, 4.2% of total strain to failure, 126 Gpa of Young's modulus and 16%IACS of electrical conductivity (EC). As for the WD Cu-4 at% Zr alloy, it was able to be wire-drawn down to 27 μm in diameter with η = 9.4.rnBoth UTS and Young's modulus increase linearly with the drawing ratio η. One of the reasons to indicate the high strength will be the development of nano-sized lamellar structure of a-Cu and Cu9Zr2 inter-metallic compound phase. Furthermore it was observed that nano-sized amorphous phase was formed within the nano-sized layer of Cu9Zr2 inter-metallic compound phase. Increase of the strength for heavily WD of Cu-4 and -5 at% Zr alloy wires will be due to the synergistic effect of deformation twins developed in the a-Cu phase and the formation of the nano-sized lamellar structure consisting of a-Cu and CugZr2 inter-metallic compound phases.rnThe highly EC of 16%IACS obtained for the WD Cu-5 at% Zr alloy wire can be explained by few dislocations in the high conductive a-Cu phase.%電子楔器の小型化や高機能化が進み，導電部品に使用されrnる銅合金にはますます高強度かつ高導電性が求められていrnる．本研究が対象とした銅合金線材には高導電性を重要視しrnた研究開発が多く1，2），高強度を目指した例は少ない．細線rn材の場合には，伸線加工した後も撚り線などに二次加工されrnることが多く，断線による生産性の低下が懸念されるたrnめ3），より高強度な銅合金線材が望まれている．