为了研究锆合金中β-Nb第二相粒子的腐蚀行为,利用真空非自耗电弧炉熔炼了2种β-(Nb, Zr)第二相合金,分别为90Nb-10Zr合金和50Nb-50Zr合金,在静态高压釜中进行360 ℃、18.6 MPa、去离子水的腐蚀实验,利用带EDS的SEM和TEM分析腐蚀生成氧化膜的显微组织。结果表明：90Nb-10Zr合金与50Nb-50Zr合金的氧化产物都为非晶氧化物与晶态氧化物,其中90Nb-10Zr合金腐蚀生成的晶态氧化物为单斜结构的Nb2O5,而50Nb-50Zr合金腐蚀生成的晶态氧化物为四方结构的(Zr, Nb)O2。
Zirconium alloys are widely used as fuel cladding materials in water-cooled nuclear power reactors due to their low thermal neutron cross-section, good mechanical properties and corrosion resistance. The waterside corrosion is one of main factors that influence the service life of zirconium alloys. The corrosion of zirconium alloys occurs at the oxide/metal (O/M) interface, so the characteristics of the oxide film do have an impact on the oxidation process of zirconium alloys, which are affected by the oxidation behavior of second phase particles (SPPs) in zirconium alloys. E110 (Zr-1Nb, mass fraction, %) and M5 (Zr-1Nb-0.16O) alloys are Zr-Nb series alloys used in commercial presently. The major SPPs in Zr-Nb series alloys are bcc β-Nb. β-Nb SPPs in zirconium alloys are very fine, and it is inconvenient to analyze their oxidation processes due to the effect of α-Zr matrix. Therefore, based on the composition and crystal structure of β-Nb, two kinds of β-(Nb, Zr) SPPs alloys, 90Nb-10Zr and 50Nb-50Zr alloys were prepared by vacuum non-consumable arc smelting, and were corroded in autoclave with deionized water at 360 ℃ and 18.6 MPa for 11 d. XRD was used to analyze the crystal structure and phase composition of β-(Nb, Zr) specimens before and after oxidation. SEM and TEM equipped with EDS were used to investigate the microstructures of the external surface and the cross-section of oxide layers. Results show that the 90Nb-10Zr and 50Nb-50Zr alloys are oxidized into amorphous and crystalline oxides. The crystalline oxide formed on 90Nb-10Zr alloy is monoclinic Nb2O5, but the crystalline oxide formed on 50Nb-50Zr alloy is tetragonal (Zr, Nb)O2.
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