A study of low cycle fatigue properties of low activation materials for fusion reactors

为了研究低活化铁素体钢（9 Cr-2 W钢，JLF-1）的疲劳性能，在轴向应变控制的完全推拉条件下，进行了室温空气中的低周疲劳试验。应变速率为0.4%/s。在初始的20次循环中，材料表现为循环应变硬化，然后逐渐发生循环应变软化，直至最终破坏，但塑性应变范围变化不大。滞后曲线中的拉伸峰值应力在大约一半的循环次数到失败取决于总应变范围，和峰值应力的降低由循环应变软化在较小的总应变范围是大于在较大的应变范围。用Manson-Coffin方程拟合了总应变幅与疲劳寿命的回归曲线，并将JLF-1钢与8 Cr2 W钢的疲劳寿命进行了比较。结果表明，JLF-1的疲劳性能优于8 C钢，具有上级性能 关于我们 r-2 W钢（F82 H）。采用电子束熔炼和真空电弧重熔工艺制备了高纯钒合金V-4Cr-4 Ti（NIFS-HEAT-2）。在此基础上，通过实验成功地制备出了26 mm厚的板材。从接骨板上机加工出正常尺寸的样本，以研究力学性能。在室温下，在空气和真空（约10 × 4Pa）环境中进行拉伸试验和断裂韧性试验。该合金在两种环境下均表现出较高的塑性，延伸率均在80%以上，断口均出现明显的韧窝断裂。在断裂韧性试验过程中没有观察到延性裂纹扩展。抗裂性曲线呈直线上升，与斜率为2 × σ流的钝化线基本一致，钝化持续了几百个J值（MJ/m2）。这意味着材料非常坚韧，并且在室温下无法获得有效的J。本研究结果有助于提高对低活化候选材料的疲劳和断裂性能的理解，以及在疲劳和断裂韧性评价实验中的尺寸效应。少

To investigate fatigue property of a low activation ferritic steel (9Cr-2W steel, JLF-1), low cycle fatigue tests were performed in air at room temperature under an axial strain control of a complete push-pull condition. The strain rate was 0.4 %/s. Cyclic strain-hardening was observed within initial 20 cycles, and then cyclic strainsoftening occurred gradually until the final failure, though the plastic strain range did not change remarkably. Tensile peak stresses in hysteresis curves measured at around a half of number of cycles to failure depended on the total strain range, and the decrease of the peak stress by the cyclic strain-softening in the smaller total strain range was larger than that in the larger strain range. The regression curve of the total strain range against the fatigue life was formulated using Manson-Coffin's equation and the fatigue life ofJLF-1 steel was compared with that of 8Cr2W steel. It was shown that JLF-1 has a superior fatigue properties to those of a 8C … More r-2W steel (F82H). A high purity vanadium alloy, V-4Cr-4Ti, NIFS-HEAT-2, was produced using electron beam melting and vacuum arc re-melting process. The impurity was tried to reduce as little as possible and a 26 mm thick plate was fabricated successfully. The normal size specimens were machined out of the plate to investigate the mechanical properties. Tensile tests and fracture toughness tests were conducted in air and in vacuum (about 10〜4 Pa) environment at room temperature. The alloy showed high ductility and elongated over 80 %, and clear dimple fracture occurred in both environments. A ductile crack growth was not observed during the fracture toughness tests. The crack resistance curve went up straightly, and it was almost same as the blunting line of which slope was 2 x σflow The blunting continued over several hundreds of J value in MJ/m2. It means that the material is very tough and the valid J cannot be obtained at room temperature. The present results contributed to enhancing understanding on fatigue and fracture properties of the low activation candidate materials and on the size effects in the fatigue and the fracture toughness evaluation experiments. Less