Zn元素及时效工艺对2056铝合金局部腐蚀行为的影响Effects of Zn element and aging process on local corrosion behavior of 2056 aluminum alloy

通过晶间腐蚀(IGC)、剥落腐蚀(EXCO)实验及透射电镜(TEM)和扫描电镜(SEM)分析，研究Zn元素及时效工艺对2056铝合金抗晶间腐蚀性能和抗剥落腐蚀性能的影响。结果表明：2056铝合金在T6(175℃)时效态下，随着时效时间的延长，其晶间腐蚀与剥落腐蚀敏感性逐渐降低；在T8(155℃)峰时效态和T3(室温)时效态下，合金的抗晶间腐蚀及抗剥落腐蚀性能均有所提高，且在T3态下2056铝合金的抗腐蚀性能最好；在T6峰时效态下，不添加Zn的2056铝合金比添加Zn的2056合金的抗腐蚀性能差。合金发生局部腐蚀与晶界及其附近区域的特征紧密相关，当晶界析出相(S(S′)相)呈链状分布且晶界无沉淀析出带(PFZ)较宽时，合金晶间及剥落腐蚀敏感性大；晶界析出相尺寸越大，分布越不连续，PFZ越窄，合金晶间及剥落腐蚀敏感性越小；当晶界无析出相和PFZ时，合金晶间及剥落腐蚀敏感性最小。

The effects of Zn element and aging process on intergranular corrosion resistance and exfoliation corrosion resistance of 2056 aluminum alloy were investigated by intergranular corrosion(IGC) experiments, exfoliation corrosion(EXCO) experiments and transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The results show that the intergranular corrosion and exfoliation corrosion susceptibility reduce gradually with further aging at T6 temper (175 ℃) for 2056 aluminum alloy. At T3 temper (room temperature) and peak-aging T8 temper (155 ℃), intergranular corrosion resistance and exfoliation corrosion resistance of 2056 aluminum alloy improve a lot, while the alloy possesses the best corrosion resistance at T3 temper. 2056 alloy with Zn addition has a better corrosion resistance at peak-aging T6 temper than the alloy without Zn addition. Local corrosion resistance is closely related with the grain boundary and the adjacent periphery. When the precipitation of equilibrium phases along the grain boundaries distributes continuously and the precipitate free zone (PFZ) is wide, the 2056 Al alloy possesses high intergranular corrosion and exfoliation corrosion susceptibility. When the alloy possesses larger size of precipitation of equilibrium phases along the grain boundaries and narrower PFZ, the alloy will achieve better intergranular corrosion resistance and exfoliation corrosion resistance. When there is nothing around the grain boundaries, the alloy has the best corrosion resistance.

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