中文摘要：

ITERTF线圈导体采用CICC（cable-in-conduit conductors）结构，其铠甲采用316LN奥氏体不锈钢圆管．ITERTF导体制备需要穿缆、缩管、650℃／200h热处理、磁体绕制等工艺．ITERTF超导线圈使用超I隘界氦冷却（4．5K），因此需要研究此温度下铠甲材料的力学性能尤其是拉伸性能．我们前期研究表明：热处理后316LN奥氏体不锈钢铠甲材料的低温（4．2K）断裂延伸率为15％左右，这低于ITER设计要求．通过优化固溶处理制度，经冷作变形及热处理后316LN奥氏体不锈钢铠甲材料的低温断裂延伸率显著提高到34％．研究结果表明优化的固溶处理工艺使316LN奥氏体不锈钢晶粒细化、晶粒均匀，从而提高了材料低温断裂延伸率．本文还对晶粒度对316LN不锈钢低温拉伸断裂行为的影响进行了阐述．

英文摘要：

The cable-in-conduit conductors （CICCs） for ITER toroidal field （TF） coils selects austenitic 316LN austenitic stainless steel as jacket material, which requires post-aging treatment at 650 ℃over 200 hours for Nba Sn superconducting materials. Special mechanical properties of the 316LN jacket material at the operating temperature of the TF magnet are required due to the high electromagnetic forces. Our previous investigations indicated that theelongation of the 316LN jacket material at 4. 2 K was around 15~//00, which does not satisfy ITER＇s requirement. However, the elongation at failure of the 316LN jacket material at 4. 2 K is found to be increased to around 34~ with optimized solution annealing treatment approach. In the present work, metallographic investigations were per- formed on both un-optimized and optimized solution annealed austenitie 316LN stainless steel and the influences of homogeneity of grains on the elongation at failure at 4. 2K is interpreted. Results indicate that the optimized solution annealing treatment can improve the homogeneity of the grains, which results in the increase of the elongation at failure at cryogenic temperature.