摘要
通过晶间腐蚀、剥落腐蚀和极化曲线试验,结合扫描电镜和透射电镜等分析手段,研究了含钪Al-Cu-Li-Zr合金在不同时效状态下的晶间腐蚀和剥落腐蚀行为。结果表明,合金在自然时效状态下具有较好的抗晶间腐蚀和剥落腐蚀能力,但随着时效时间的延长,其晶间腐蚀与剥落腐蚀倾向逐渐增加;在4.0mol/LNaCl+0.1mol/LHNO3+0.4mol/LKNO3(EXCO)溶液中进行的极化曲线测试也表现出相同的趋势。透射电镜观察表明,自然时效态合金未析出Γ1相,欠时效态合金中有少量细小短棒状Γ1相析出,随着时效时间的延长,Γ1相逐渐粗化,过时效时合金中出现较宽的无沉淀带(PFZ)。由于合金中Γ1相和PFZ的开路电位都比铝基体低,在腐蚀过程中作为阳极相优先溶解,从而引起合金晶间腐蚀和剥落腐蚀。
As a promising neotype high-mass structural material of wide acceptance in aerospace and aviation industries, Sc-containing Al-Cu-Li-Zr based alloy has outstanding mechanical properties, weldability, and corrosion resistance. Thus Al-3.5Cu-1.5Li-0.22(Sc+Zr) alloy was prepared making use of ingot metallurgy. The intergranular corrosion and exfoliation corrosion behavior of the resulting alloy subject to different modes of aging was investigated. The polarized curves of the alloy were measured, while the microstructures of the as-cast and corroded alloy were analyzed by means of scanning electron microscopy and transmission electron microscopy. It was found that the naturally-aged alloy had the best intergranular and exfoliation corrosion resistance. The intergranular and exfoliation corrosion of the alloy was accelerated with prolonging aging duration, which conformed to the relevant polarization test results of the alloy in a mixed acidic solution composed of 4.0 mol/L NaCl+0.1 mol/L HNO_ 3 +0.4 mol/L KNO_ 3 . In terms of the microstructure of the alloy, no Γ_ 1 phase was precipitated in the naturally-aged sample. Contrary to the above, a small amount of bar-like fine Γ_ 1 phase was precipitated in the under-aged sample whose Γ_ 1 phase coarsened with increasing aging duration. Moreover, some equilibrium phases and precipitation free zone (PFZ) were observed in the over-aged sample. Since the PFZ and Γ_ 1 phase had more negative open-circuit potentials than the Al matrix, they could act as anodes in corrosive media and be dissolved preferentially. This might account for the intergranular and exfoliation corrosion of the titled alloy.
出处
《材料保护》
CAS
CSCD
北大核心
2006年第10期1-4,共4页
Materials Protection
基金
国家"863"计划项目(2002AA305104)
关键词
含Sc铝锂合金
晶间腐蚀
剥落腐蚀
电化学
Sc-containing Al-Li alloy
intergranular corrosion
exfoliation corrosion
electrochemistry
