(华中科技大学 材料成形与模具国家重点实验室，武汉 430074)
摘 要: 研究压铸AlMg5Si2Mn合金的电化学腐蚀、晶间腐蚀和腐蚀疲劳机理。结果表明：合金的自腐蚀电位和点蚀电位分别为-1220和-690 mV，钝化区间约为530 mV，说明合金的耐腐蚀性能良好。合金的晶间腐蚀倾向明显，这主要是由于Mg2Si相自腐蚀电位较低，且(Al+Mg2Si)共晶区的体积分数较大(29.6%)。电化学腐蚀反应和Mg2Si自身溶解产生的氢元素导致疲劳试样表面发生阳极溶解，加速了疲劳裂纹的萌生，从而显著降低了合金的疲劳寿命。腐蚀疲劳试样的裂纹主要是沿晶界扩展。氢元素也导致合金塑性下降，造成应力腐蚀开裂。
关键字: 铝合金；压力铸造；腐蚀疲劳；极化；断口形貌
（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
