(華中科技大學(xué) 材料成形與模具國家重點實驗室，武漢 430074)
摘 要: 研究壓鑄AlMg5Si2Mn合金的電化學(xué)腐蝕、晶間腐蝕和腐蝕疲勞機理。結(jié)果表明：合金的自腐蝕電位和點蝕電位分別為-1220和-690 mV，鈍化區(qū)間約為530 mV，說明合金的耐腐蝕性能良好。合金的晶間腐蝕傾向明顯，這主要是由于Mg2Si相自腐蝕電位較低，且(Al+Mg2Si)共晶區(qū)的體積分數(shù)較大(29.6%)。電化學(xué)腐蝕反應(yīng)和Mg2Si自身溶解產(chǎn)生的氫元素導(dǎo)致疲勞試樣表面發(fā)生陽極溶解，加速了疲勞裂紋的萌生，從而顯著降低了合金的疲勞壽命。腐蝕疲勞試樣的裂紋主要是沿晶界擴展。氫元素也導(dǎo)致合金塑性下降，造成應(yīng)力腐蝕開裂。
關(guān)鍵字: 鋁合金；壓力鑄造；腐蝕疲勞；極化；斷口形貌
（State Key Laboratory of Materials Processing and Die & Mould Technology,
Huazhong University of Science and Technology, Wuhan 430074, China）
Abstract:The electrochemical corrosion, intergranular corrosion and corrosion-fatigue mechanisms of die cast AlMg5Si2Mn alloy were studied. The results indicate that the self-corrosion potential and pitting potential are -1220 and -690 mV, respectively. The wide domain of passivity (of about 530 mV) indicates good corrosion resistance of the alloy. The poor intergranular corrosion resistance of the alloy is attributed to the low corrosion potential and high volume fraction (29.6%) of (Al+Mg2Si) eutectic region. Considerable hydrogen concentration, which is created by the electrochemical reaction and the dissolution of Mg2Si dendrite, results in the anodic dissolution on the surface of fatigue specimens and accelerates the premature crack initiation, thus obviously decreasing the fatigue life of the alloy. Fatigue cracks of the corroded fatigue specimens mainly propagate along grain boundaries. In addition, hydrogen reduces the ductility of the alloy and leads to stress corrosion cracking.
Key words: aluminum alloy; high pressure die cast; corrosion fatigue; polarization; fractograph
