热处理工艺对冷旋U-6.5Nb合金电化学腐蚀行为的影响

采用冷旋方法制备了管状U-6.5Nb合金零件，分别在400、600和700℃下对合金零件进行1h退火处理，考察了不同状态的U-6.5Nb合金在含50μg/gCl-的氯化钾水溶液中的电化学腐蚀行为，采用扫描电镜表征了腐蚀前后的形貌特征。结果表明：所有状态的合金均未发生钝化，冷旋态和700℃退火态合金为单相组织，具有较高的腐蚀电位和较小的腐蚀电流，400℃退火和600℃退火态合金为双相组织，具有较低的腐蚀电位和较大的腐蚀电流。单相合金比双相合金具有更好的抗腐蚀能力，但更易发生点蚀。双相合金表面Nb成分不均是其抗腐蚀性不佳的主要原因。

Effect of Annealing on Electrochemical Corrosion Behavior for Cold Spinned U-6.5Nb Alloy

Tubular U-6.5Nb alloy part was fabricated by cold spinning. The as-spinned alloys were then annealed at 400, 600 and 700 ℃ for 1 h, respectively. The electrochemical corrosion behaviors in aqueous solution containing 50 μg/g Cl－ were examined. Scanning electron microscope was used to characterize the surface morphology and microstructures of U-6.5Nb alloy. The single phase alloys, including as-spinned alloy and as-annealed alloy at 700 ℃ have higher corrosion potentials and smaller corrosion currents, and that the dual-phase alloy annealed at 400 and 600 ℃ has lower corrosion potentials and greater corrosion currents. Single phase alloys are more resistant to corrosion than dual-phase alloys. Pits corrosion occurs on the surface of single-phase alloys, while homogeneous corrosion occurs on the surface of dual-phase alloys. The inhomogeneous distribution of Nb in the dual-phase alloy is responsible for its poor corrosion resistance.