熔焊接头组织抗辐照损伤机制研究

The issues, including the irradiation embrittlement, irradiation swelling, irradiation-induced stress cracking, which are prone to appear on the weld joints of the core structural material under irradiation in the nuclear fusion, are to be investigated. In order to investigate the formation and evolution mechanism of metal crystal microdefects induced by irradiation, helium ions irradiation will be used to simulate the process of neutron irradiation by controlling the irradiation-induced damage energy; an analysis of alloying elements distribution and irradiation segregation near grain boundaries before and after irradiation is conducted to reveal the mechanism of irradiation-induced diffusion of alloying elements ; the influence of irradiation-induced microstructure variation on macrostructure and properties is explored; the relationships among the microstructure transformation of weld joint, variation on mechanical properties, the microdefects of crystals and the diffusion of alloying elements are established, and the anti-irradiation embrittlement mechanism of weld joint is revealed; the anti-irradiation swelling mechanism of welding joint is to be studied by exploring the influence of He, one of the nuclear reaction products, on the formation and growth of weld metal cavities; the mechanism of anti-irradiation induced stress cracking in welded joints is to be studied by analyzing the influence of the distribution of residual stress on the irradiation-induced stress cracking in welded joints. A major goal of this project is to reveal the mechanism of anti-irradiation embrittlement, irradiation swelling and irradiation-induced stress cracking of weld joint, and provide the basic theory to improve the resistance to irradiation-induced damage performance and service life of key components in nuclear reactor.

针对聚变堆芯结构材料熔焊接头在辐照环境中，易出现的辐照脆化、辐照肿胀及辐照诱发应力开裂问题进行研究。采用氦离子辐照来模拟中子辐照过程，通过控制辐照损伤能量，研究辐照诱发焊缝金属晶体微观缺陷的形成和演化机理；分析辐照前后晶界附近合金元素分布、辐照偏析等情况，揭示辐照诱发焊缝合金元素扩散机理；探索辐照诱发微观结构变化对宏观组织及性能的影响规律；建立辐照诱发焊缝组织转变、韧脆转变与晶体微观缺陷、合金元素扩散之间的理论关系，研究熔焊接头抗辐照脆性机理；探索核反应产物He对焊缝组织中空洞形成及长大的影响规律，研究熔焊接头抗辐照肿胀机理；分析熔焊接头中残余应力的分布情况对辐照诱发应力开裂敏感性的影响规律，研究熔焊接头抗辐照诱发应力开裂机理。本项目旨在揭示熔焊接头组织抗辐照脆化、辐照肿胀及辐照诱发应力开裂机理，为提高核反应堆关键部件的抗辐照损伤性能及服役寿命奠定理论基础。

316L奥氏体不锈钢与CLAM钢作为反应堆工程建设中极具应用潜力的钢种，探究其焊缝金属在辐照条件下缺陷的演变过程、元素偏析情况以及力学性能的变化，具有重要的理论意义与实用价值。本项目研究了辐照诱发的焊缝组织状态变化及其对辐照脆性的影响；辐照参数对焊缝金属中微观结构缺陷及辐照肿胀的影响；辐照参数对焊缝金属元素扩散和辐照偏析的影响；应力对辐照诱发开裂的影响规律。研究了不同焊接方法和调质处理工艺对焊缝金属抗辐照损伤性能的影响规律。分析了超声电弧复合TIG工艺对焊缝金属抗辐照损伤性能的提升作用。.研究表明，辐照后316L不锈钢焊缝金属中未有新相产生，随着辐照剂量的升高（从5×1015ions/cm2到1×1017ions/cm2），焊缝金属表面产生的空洞数量从1.6×1012m-2增加到1.0×1013m-2，空洞平均直径从21.9nm增大到29.4nm。氦泡数的密度从1.9×1016m-2增加到2.2×1016m-2，氦泡的平均直径从2.7nm增大到3.8nm；位错环数密度从2.9×1014m-2增加到5.8×1014m-2，辐照硬化程度增大，Cr、Mo、Mn原子从晶界向晶粒内部扩散，在晶界处产生贫化，Ni、Si两种原子从晶粒内部向晶界聚集，在晶界处产生富集。应力作用下焊缝金属的辐照脆化敏感性降低。.辐照剂量从5×1015ions/cm2增大到1×1017ions/cm2时，CLAM钢焊缝金属空洞数量从1.5×1012m-2增加到9.7×1012m-2，空洞平均直径从21.4nm增大到25.7nm。氦泡数的密度从1.7×1016m-2增加到2.0×1016m-2，氦泡的平均直径从2.6nm增大到3.5nm；位错环数密度从2.7×1014m-2增加到5.5×1014m-2。焊缝金属的最大载荷值从77.7mN增大到131.4mN；辐照后焊缝金属中Cr、W、Mn在晶界处产生贫化，Si原子在晶界处产生富集。.对比了SAW、SMAW和TIG三种焊接方法获得的316L焊缝金属经相同剂量的辐照后的损伤程度，SAW焊缝金属的损伤程度最高，TIG焊缝金属损伤程度较低。超声电弧复合TIG工艺使焊缝金属抗辐照损伤能力得到进一步提高。