290℃氩离子辐照对Fe-Cu合金微观组织的影响

Effects of Ar Ion Irradiation on Microstructure of Fe-Cu Alloys at 290℃

在290℃对固溶态Fe-1.3%Cu(原子分数)合金进行4×10^(16) ion/cm^(2)注量氩离子辐照,用TEM观察样品微观组织,用原子探针表征溶质原子分布。结果表明,辐照层内形成大量黑斑缺陷,距辐照表面500~600 nm深度处存在直径1.3 nm的气泡。辐照层内存在富Cu团簇,随深度增加团簇尺寸和数量密度先增加后降低。这是由于高损伤剂量率与大尺寸级联碰撞共同作用抑制Cu原子偏聚,使近表面处富Cu团簇尺寸小、数量少,损伤剂量峰附近氩离子浓度增加,形成Ar-V团簇,长大过程中拖拽Cu原子进行迁移,促进富Cu团簇形成和长大。

Irradiation-enhanced precipitation of Cu clusters is a main factor contributing to the hardening/embrittlement of reactor pressure vessels,and thus,limiting the lifetime of reactors.The Cu clusters are easily formed in ferric alloys under neutron irradiation or ion irradiation,which is used to simulate neutron irradiation.However,the inhibition and even dissolution of Cu clusters in Cu-containing alloys after ion irradiation is also observed in some research.To investigate the reason for ion irradiation-induced dissolution of solute clusters,Fe-1.3%Cu(atomic fraction)alloys were irradiated with Ar ions to the fluence of 4×10^(16) ion/cm^(2) at 290℃.TEM and atom probe tomography were used to characterize microstructure and solute atom distributions,respectively.Numerous black dot defects and bubbles with average diameters of about 1.3 nm are observed in the irradiated layer.Well-defined Cu-rich clusters are also precipitated in the irradiated layer.The average radius and number density of clusters increase first and then decrease with an increase in distance from the surface.The high displacement damage rate and large cascade size of Ar ions inhibit the irradiation-enhanced diffusion of Cu atoms and bring Cu atoms of the clusters back to matrix, which causes Cu clusters to precipitate weakly near the irradiated surface.With increasing distance from the surface, the Ar ion concentration increases. Ar-vacancy complexes orAr bubbles form due to the aggregation of Ar ions. Then, the interattraction between Cu atoms and vacanciescomplexes would enhance the atom diffusion and segregation, which causes an increase in size andnumber density of the Cu-rich clusters.