Study on the early-stage of copper-rich nano-clusters precipitation in model nuclear reactor pressure vessel steel
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摘要: 采用調質處理后熱時效模擬方法,用原子探針層析成像技術研究了核反應堆壓力容器模擬鋼中富銅納米團簇的析出過程.模擬鋼經880℃加熱水淬,660℃高溫回火調質處理,并經400℃時效處理1000 h后基體中析出了富銅納米團簇.使用MSEM(maximum separation envelope method)方法重點研究了富銅納米團簇在析出早期階段成分變化規律.結果表明,富銅納米團簇容易在鎳含量較高的位置形核,并隨著富銅納米團簇中銅原子聚集程度的增加,納米團簇中心處銅含量逐漸增加,鎳含量逐漸減少;在納米團簇與α-Fe基體界面處,鎳和錳含量逐漸增加,形成了富鎳和富錳包裹富銅納米團簇的結構.結合實驗結果討論了壓力容器鋼中合金元素鎳及雜質元素磷會增加中子輻照脆化敏感性的原因.Abstract: Early-stage formation of Cu-rich nano-clusters in thermal aging nuclear reactor model pressure vessel steel quenched and tempered was investigated by atom probe tomography(APT).After the initial heat treatment at 880 ℃ for 0.5 h and water quenching,the materials were tempered for 10 h at 660 ℃ and air cooled.Cu-rich nano-clusters were observed in the samples aged at 400 ℃ for 1 000 h.The change in composition of the steel in the early-stage of precipitation of Cu-rich nano-clusters was studied by the maximum separation envelope method(MSEM).Cu nanoclusters are observed to form from high nickel regions.The Cu concentration increases and the Ni concentration decreases at the central cores with increasing Cu atoms congregation.Ni and Mn atoms aggregation on the exterior side of the cluster/matrix interface is also evident.Based on experimental results,the reason that Ni and P can increase the sensitivity to neutron irradiation embrittlement of the nuclear reactor pressure vessel steel is discussed.
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