( 中南大學 材料科學與工程學院， 長沙 410083)
摘 要: 研究了2195鋁鋰合金在不同時效狀態(tài)下的晶間腐蝕和剝落腐蝕行為。結果表明： 2195合金在自然時效狀態(tài)下具有較好的抗晶間腐蝕和剝落腐蝕能力，但隨著在160℃時效時間的延長， 其晶間腐蝕與剝落腐蝕傾向逐漸增加；在剝落腐蝕溶液中進行的極化曲線測試也表現(xiàn)出相同的趨勢。 透射電鏡觀察發(fā)現(xiàn)： 2195合金主要析出相為T1相； 隨著時效時間延長， T1相逐漸粗化， 在晶界處還會出現(xiàn)無析出帶及平衡相。模擬相實驗證實， 由于T1相和無析出帶的開路電位都明顯低于鋁基體的，在腐蝕性介質中作為陽極相優(yōu)先溶解， 從而導致2195合金產生晶間腐蝕及剝落腐蝕。過時效狀態(tài)與峰時效狀態(tài)相比， 晶界平衡相增多， 無析出帶變寬， 晶間腐蝕及剝落腐蝕程度將更加嚴重。
關鍵字: Al-Li合金；時效； 腐蝕； 電化學
LI Jin-feng, LI Hai, LI Yan-fen
（ School of Materials Science and Engineering,
Central South University, Changsha 410083, China）
Abstract: Intergranular corrosion and exfoliation corrosion behavior of 2195 Al-Li alloy with different aging treatment schemes were studied. The results show that the naturally-aged 2195 alloy has the best intergranular and exfoliation corrosion resistance. The intergranular and exfoliation corrosion are accelerated with prolonging the increasing aging time at 160℃, which is in accord with the results of polarization tests in IGC solution. Microstructure observations show that the main precipitate of 2195 Al-Li alloy is T1 phase. With the aging time increasing, T1 phase coarsens, and precipitate-free-zone(PFZ) and equilibrium phases are observed along grain boundaries. It is shown by open-circuit potential measurements that the open-circuit potentials of PFZ and T1 phase are more negative than that of Al matrix. They act as anodes in corrosive media and dissolve preferentially. These cause the intergranular and exfoliation corrosion of 2195 alloy. Compared with the peak-aged alloy, the over-aged alloy contains more equilibrium phases at the grain boundaries and wider PFZ, and thus suffers from faster intergranular and exfoliation corrosion.
Key words: Al-Li alloy; aging; corrosion; electrochemistry
