(上海交通大學(xué) 金屬基復(fù)合材料國家重點(diǎn)實(shí)驗(yàn)室，上海 200240)
摘 要: 采用AlCl3-NaCl熔鹽，在較低溫度(380 ℃)下對AZ91D鎂合金表面進(jìn)行熱擴(kuò)散滲鋁處理，制備一擴(kuò)散合金層。采用金相顯微鏡、掃描電子顯微鏡、X射線能量色散儀、X射線衍射儀，對所得的擴(kuò)散合金層的組織和結(jié)構(gòu)進(jìn)行分析；采用納米壓痕儀分析表面合金層的硬度；采用交流阻抗及極化曲線分析在3.5%(質(zhì)量分?jǐn)?shù))NaCl溶液中進(jìn)行熔鹽冶金擴(kuò)散處理前、后AZ91D鎂合金的耐腐蝕性能。結(jié)果表明：AZ91D鎂合金經(jīng)熔鹽冶金擴(kuò)散處理后，在較低溫度下，即可獲得連續(xù)致密的表面合金層；合金層主要由外層的Mg2Al3與內(nèi)層的Mg17Al12金屬間化合物組成，該表面合金層的形成伴隨著熔鹽中置換反應(yīng)及擴(kuò)散過程的發(fā)生；合金層顯著提高合金的表面硬度，并明顯改善AZ91D鎂合金在3.5%(質(zhì)量分?jǐn)?shù))NaCl溶液中的耐腐蝕性能。
關(guān)鍵字: AZ91D鎂合金；熔鹽；擴(kuò)散；硬度；耐蝕性
aluminizing coating on surface of AZ91D Mg alloy
（State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, Shanghai 200240, China）
Abstract:The aluminizing of AZ91D Mg alloy by AlCl3-NaCl molten salts at a lower temperature of 380 ℃ were investigated, and a diffusion alloyed layer was prepared. The microstructure and composition of the diffusion alloyed layer were studied by optical microscopy, scanning electron microscopy, energy dispersive spectrum and X-ray diffractometry. The nano-hardness of the alloyed layer was studied by nanoindentation. The corrosion resistance of the treated AZ91D Mg alloy was evaluated in 3.5% (mass fraction) NaCl solution by electrochemical impedance spectroscopy and potentiodynamic polarization. The results show that a continuous and dense alloyed layer can be formed on the surface of the AZ91D Mg alloy by aluminizing in molten salts at low temperature. The aluminum-alloyed layer consists mainly of Mg2Al3 and Mg17Al12 intermetallic layers. The formation of the Mg-Al alloyed layer is associated with a displacement reaction mechanism and diffusion process that takes place during the molten salt treatment. The alloyed layer substantially improves the hardness as well as the corrosion resistance of the AZ91D Mg alloy, which is attributed to the high volume fraction of intermetallic compounds in the surface alloyed layer.
Key words: AZ91D Mg alloy; molten salt; diffusion; hardness; corrosion resistance
