(1. 湖南工業(yè)職業(yè)技術(shù)學(xué)院 機械工程系，長沙 410208；
2. 南車戚墅堰機車車輛工藝研究所有限公司，常州 213011；
3. 中南大學(xué) 材料科學(xué)與工程學(xué)院，長沙 410083)
摘 要: 采用光學(xué)顯微鏡(OM)、掃描電鏡(SEM)和能譜分析(EDS)等手段研究擠壓時效態(tài)MB8鎂合金在鹽水浸泡條件下的腐蝕特征，并探討合金的腐蝕機理。結(jié)果表明：合金以絲狀腐蝕和點蝕這兩種局部腐蝕為主要的腐蝕形式。合金經(jīng)過一定時間的誘導(dǎo)期后發(fā)生絲狀腐蝕，腐蝕前端的絲頭處發(fā)生鎂基體的陽極溶解，已發(fā)生腐蝕的絲尾處作為活性陰極發(fā)生析氫反應(yīng)；第二相粒子對絲狀腐蝕的擴展具有重要影響，橫截面上絲狀腐蝕隨著彌散分布的第二相粒子向四周擴展，而縱截面上腐蝕絲隨著第二相粒子的帶狀分布呈長條帶狀形貌特征；在絲狀腐蝕還未擴展到的區(qū)域由于第二相粒子與基體之間的腐蝕微電偶作用導(dǎo)致基體發(fā)生陽極溶解，從而產(chǎn)生點蝕。
關(guān)鍵字: MB8鎂合金；第二相；絲狀腐蝕；鹽水浸泡；腐蝕
（1. Department of Mechanical Engineering, Hunan Industry Polytechnic, Changsha 410208, China;
2. CSR Qishuyan Institute Co., Ltd., Changzhou 213011, China;
3. School of Materials Science and Engineering, Central South University, Changsha 410083, China）
Abstract:The corrosion characteristics and corrosion mechanism of aged extrude MB8 magnesium alloy immersed in saline solution were investigated by optical microscopy (OM), scanning electron microscopy (SEM) and energy dispersive X-ray spectrometry (EDS). The results show that filiform corrosion and pitting corrosion are the main corrosion forms for MB8 alloy. After an induction period, filiform corrosion occurs coupling with anodic Mg dissolution at the leading edge of the corrosion front and hydrogen evolution on a cathodically activated corroded region behind. The second phases show significant effect on the propagation of filiform corrosion. The filiform corrosion grows in all directions due to the dispersively distributed second phases in the cross section, while the corrosion filament extends like bands due to the second phases distributed in bands in the longitudinal section. In the region without filiform corrosion, pitting occurs due to the galvanic effect of Mg matrix coupled with second phase particles.
Key words: MB8 magnesium alloy; second phases; filiform corrosion; saline immersion; corrosion
