Practical Bronze Alloy for Nb 3 Sn Superconductors
Practical Bronze Alloy for Nb 3 Sn Superconductors
复制标题
Nb 3 Sn超导体实用青铜合金
DOI：
10.2221/jcsj.47.526
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发表时间：
2012
期刊：
影响因子：
--
通讯作者：
A. Kikuchi
中科院分区：
文献类型：
--
作者：
H. Taniguchi;A. Kikuchi
铜锡（Cu-Sn）青铜合金是青铜化Nb 3Sn超导线材的关键材料。日本大坂合金工厂建立了一种独特的大型青铜合金熔炼工艺，称为“水田法”。在该过程中，通过使含有热熔融金属的石墨坩埚直接通过水淋浴器来冷却石墨坩埚。不需要一般的模具铸造，因此仅发生热熔融金属的轻微氧化。由于使用单向凝固工艺，因此获得了非常均匀的锡浓度，而在铸锭的纵向方向上没有严重的反向偏析。在本文中，我们研究了具有14，15和16质量%的Sn浓度的实际青铜的显微组织和力学性能的细节。延伸率，0.2%的韧性，维氏硬度在室温下，连续冷拉极限作为中间退火的函数进行了研究。冷拉性能的退化是过度的，与一个相当低的退火温度为400 ℃。我们发现，许多细小的析出物出现在低温退火后的α晶内和α晶间。透射电子显微镜分析表明，这些沉淀物是δ相（Cu 41 Sn 11）。δ析出相可能是青铜合金塑性变形中滑移运动的钉扎点。我们必须重新认识到，中间退火温度是一个非常重要的参数，以避免在工业生产中的青铜处理的Nb 3Sn超导体的断线。
Synopsis: Copper-Tin (Cu-Sn) bronze alloy is the key material for bronze-processed Nb3Sn superconducting wires. The Osaka Alloying Works in Japan has established a unique melting process for large-scale bronze alloys called the “Mizuta method”. In this process, the graphite crucible containing hot molten metal is cooled by passing it directly through a water shower. A general mold casting is not needed, so only slight oxidation of the hot molten metal occurs. Since a uni-directional solidification process is used, a very homogeneous tin concentration without severe inverse segregation in the longitudinal direction of the ingots is obtained. In this paper, we investigate the microstructure and mechanical performance details of the practical bronze having Sn concentrations of 14, 15 and 16 mass%. Elongation, 0.2% toughness, Vickers hardness at room temperature, and the limit of continuous cold-drawability as a function of intermediate annealing were studied. Degradation of cold-drawability was excessive, with a rather low annealing temperature of 400C. We found that numerous fine precipitates appeared at the intraand inter-alpha grains after low-temperature annealing. The transmission electron microstructure analysis revealed that those precipitates were the delta phase (Cu41Sn11). The delta precipitates may behave as a pinning site of the slip motion for the plastic deformation of bronze alloys. We have to re-recognize that the intermediate annealing temperature is a very important parameter for avoiding wire breakage during the industrial production of bronze-processed Nb3Sn superconductors.