铜偏聚区的高分辨电镜分析

High-resolution Electron Microscopy Analysis of Cu-rich Clusters

研究铜在钢中的时效强化和沉淀规律具有理论意义和实用价值。应用JEM-2010高分辨电镜研究了Fe-1.18Cu、Fe-1.55Cu高纯钢在时效时组织结构的变化规律,发现,含铜高纯钢固溶处理后,在550℃、650℃时效过程中,首先在铁素体晶粒中析出含铜偏聚区,铜原子偏聚在(001)_α晶面上。在时效峰处为富铜的G.P区颗粒,其直径为4～20nm,呈层状的圆饼状,一般5～9层,富铜层和贫铜层相间分布,每一层厚度约为1～2nm。G.P区与铁素体基体半共格。G.P区的富铜区内及周边存在高密度位错和层错。在过时效初期,含铜偏聚区颗粒长大,偏聚区内富铜层和贫铜层的数量增多,富铜层厚度减小,位错密度降低。在铁素体基体上弥散分布的G.P区是含铜高纯钢时效强化的原因。

Study on aging strengthening and precipitation law of copper in steel is of significance. The change rule of the microstructure in Fe-1.18Cu and Fe-1.55Cu high purity steel during aging treatment was investigated by using JEM-2010 high-resolution electron microscope（HREM）. It was shown that Cu-rich clusters in Cu - containing high purity steel during aging at 550℃ and 650℃ after solution treatment were precipitated firstly in ferrite crystal grain and Cu atoms were clustered on （001）α planes. It was also shown that they were Cu-rich G. P zone particles at aging peak, the size of which would be about 4 - 20 nm and the appearance was layered and round cake-shaped, which whould contain 5 - 9 layer. Cu-rich layer and Cu-poor layer distributed alternately over Cu-rich G. P zone particles, each layer of which whould be about 1 - 2 nm . The G. P zone kept half-coherency with ferrite matrix. A high density of dislocations and faults was involved in or about the Cu-rich layers and Cu-poor layers of the G. P zone. At the early period of over-aging, with Cu-rich clusters particles growing up gradually, the number of Cu-rich layers and Cu-poor layers increased in these clusters while the thickness of Cu-rich layer decreased and the density of dislocations was reduced. The G. P zone distributed in ferrite matrix was the reason of aging strengthening in Cu- containing high purity steels.