时效制度对含钪超高强铝合金晶间腐蚀和剥落腐蚀的影响

Influence of Aging Treatment on Intergranular Corrosion and Exfoliation Corrosion Susceptibility of Super-high Strength Al Alloy Containing Sc

通过晶间腐蚀、剥落腐蚀和电化学腐蚀试验,结合扫描电镜和透射电镜等分析手段,研究了含钪Al-Mg-Zn-Cu-Zr合金在不同时效状态下的的晶间腐蚀和剥落腐蚀行为。结果表明,合金抗晶间腐蚀和剥落腐蚀能力随着时效时间的延长而提高,在4.0mol/L NaCl+0.1mol/L HNO3+0.4mol/L KNO3(EXCO)溶液中测试的极化曲线也表现出相同的趋势。透射电镜观察表明,晶界析出相和晶界无沉淀析出带(PFZ)是影响合金腐蚀性能的主要因素。随着时效时间的延长,非平衡相η′和S′相逐渐向平衡相η和S相转变,晶界析出相粗化并呈链状分布,PFZ变宽。晶界粗大平衡相的不均匀分布和PFZ阻断了腐蚀的阳极通道,使合金的腐蚀敏感性降低。

The influence of aging treatment on intergranular corrosion and exfoliation corrosion susceptibility of super-high strength AI alloy containing Sc was studied using optical microscopy （OM） and transmission election microscopy （TEM）. It was found that intergranular corrosion and exfoliation corrosion of super-high strength Al alloy containing Sc were accelerated with prolonging the aging time, which were in accord with the results of polarization tests in 4. 0 mol/L NaCl＋ 0. 1 mol/L HNO3 ＋0. 4 mol/L KNO3 （EXCO） solution. TEM observation shows that the size of precipitates at grain boundaries and the width of precipitate free zone （PFZ） at grain boundaries are the key factors responsible to the corrosion behavior of the alloy, As aging time was increased, η＇ and S＇ phases transformed into equilibrium r/and S phases, and the size of r/and S phases at grain boundaries and the width of PFZ were increased. The discontinuous distribution of the equilibrium phases at grain boundaries and the PFZ blocked the anodic tunnels of corrosion, which decreased the corrosion susceptibility of the alloys.