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半硬态B_(Fe30-1-1)铜镍合金管材在实海暴露过程中随着表面氧化膜的腐蚀脱落,在晶界上出现沿晶析出物,形成较大的沿晶腐蚀倾向。TEM观察表明,这种析出物是调幅分解(Spinodaldecomposition)的产物,其衍衬象为明暗相间的条纹,调幅波长小于50nm。该析出物使材料在拉伸时出现脆性沿晶断口,强度略有上升,但大大恶化了材料的耐海水腐蚀性能。文中根据试验结果阐明了析出物的生成动力,认为是海水腐蚀导致材料的应力状态改变(即应变诱生)及合金元素沿晶界向表层的扩散促使已形核的析出物粗化所致。
The semi-solid B_ (Fe30-1-1) Cu-Ni alloy pipe exfoliated along the surface oxide film during the exposure to the sea, resulting in a large intergranular corrosion in the grain boundary. TEM observation shows that this precipitate is a product of spinodal decomposition. Its diffraction pattern is like light and dark stripes, and the amplitude modulation wavelength is less than 50 nm. The precipitate makes the material brittle along the crystal fracture in tensile, the strength slightly increases, but greatly deteriorates the seawater corrosion resistance of the material. According to the experimental results, the generation of precipitates is illustrated. It is believed that seawater corrosion leads to the change of the stress state (ie, strain induced) and the diffusion of the alloying elements along the grain boundaries to the surface layer, resulting in roughening of nucleated precipitates.