Zn元素及時效工藝對2056鋁合金局部腐蝕行為的影響Effects of Zn element and aging process on local corrosion behavior of 2056 aluminum alloy

通過晶間腐蝕(IGC)、剝落腐蝕(EXCO)實驗及透射電鏡(TEM)和掃描電鏡(SEM)分析，研究Zn元素及時效工藝對2056鋁合金抗晶間腐蝕性能和抗剝落腐蝕性能的影響。結果表明：2056鋁合金在T6(175℃)時效態下，隨著時效時間的延長，其晶間腐蝕與剝落腐蝕敏感性逐漸降低；在T8(155℃)峰時效態和T3(室溫)時效態下，合金的抗晶間腐蝕及抗剝落腐蝕性能均有所提高，且在T3態下2056鋁合金的抗腐蝕性能最好；在T6峰時效態下，不添加Zn的2056鋁合金比添加Zn的2056合金的抗腐蝕性能差。合金發生局部腐蝕與晶界及其附近區域的特征緊密相關，當晶界析出相(S(S′)相)呈鏈狀分布且晶界無沉淀析出帶(PFZ)較寬時，合金晶間及剝落腐蝕敏感性大；晶界析出相尺寸越大，分布越不連續，PFZ越窄，合金晶間及剝落腐蝕敏感性越小；當晶界無析出相和PFZ時，合金晶間及剝落腐蝕敏感性最小。

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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