热老化温度对高Si含量F/M钢中Laves相析出行为和冲击性能的影响

铁素体马氏体钢(F/M钢)是铅冷快堆堆芯的主要候选材料之一，提高材料中的Si含量可提高其抗腐蚀性能，但同时会促进Laves相的析出从而影响材料韧塑性。针对一种Si含量为0.98%的F/M钢，开展了3种温度(500、550、600℃)下5000 h的热老化实验，研究了温度对Laves相析出行为和冲击性能的影响。结果表明，热老化温度升高能够促进Laves相的形核和粗化，且温度从550℃提高至600℃，Laves相的粗化速率从3.7 nm/h^1/3提高至9.0 nm/h^1/3。另一方面，热老化温度升高将加速冲击性能的退化，在550℃和600℃下热老化500 h，冲击功(AKV)值分别下降至热老化前的51%和39%，而在500℃下热老化2500 h,A_KV值仍保持热老化前的75%。Laves相的析出与冲击性能退化有强烈的对应关系，是冲击性能退化的主要原因。

Effect of Thermal Aging Temperature on Precipitation Behavior of Laves Phase and Impact Performance in High Si Content Ferritic Martensitic Steels

Ferritic martensitic steel (F/M steel) is one of the main candidate materials for lead-cooled fast reactor core. Increasing Si content can improve its corrosion resistance, but at the same time, it can promote the precipitation of Laves phase, thus affecting the toughness and plasticity of the material. For a F/M steel with a Si content of 0.98%, thermal aging experiments for 5000 h at three temperatures (500, 550 and 600℃) are carried out to study the effect of temperature on the precipitation behavior of Laves phase and impact performance. The results show that heating can promote the nucleation and coarsening of Laves phase, and with the temperature increasing from 550℃ to 600℃, the coarsening rate of Laves phase increases from 3.7 nm/h1/3 to 9.0 nm/h1/3. On the other hand, the increase of thermal aging temperature will accelerate the degradation of impact performance. After thermal aging at 550℃ and 600℃ for 500 h, the impact work (A_KV) decreases to 51% and 39% of that before thermal aging, respectively, while the A_KV value remains 75% of that before thermal aging for 2500 h at 500℃. The precipitation of Laves phase has a strong corresponding relationship with the degradation of impact performance, which is the main reason for the degradation of impact performance. egradation of impact performance.