【作者】 张波；

【导师】 董选普；

【作者基本信息】 华中科技大学 ， 材料加工工程， 2009， 硕士

【摘要】 镁合金是目前工程应用当中最轻的结构金属,广泛应用于汽车、电子、通讯、航空航天、国防军事等领域,特别易于再生利用,被称“2为1世纪的绿色工程材料”。但是镁合金的电极电位很低,未经防护的镁合金极易被腐蚀,已成为限制其广泛应用的瓶颈。镁合金的耐蚀性成了当前研究的一个焦点。首先,本文探索了采用盐浴渗铝工艺（摩尔比为1:1的NaCl-AlCl₃作为渗剂）提高镁合金耐蚀性的可行性;研究了扩散时间、扩散温度对渗铝效果的影响。研究结果表明:采用盐浴渗铝工艺提高镁合金耐蚀性是可行的;在纯镁和AZ91D的表面分别形成了最大厚度分别为15μm和50μm的合金层;合金层的主要物相为Al₁₂Mg₁₇、Al₃Mg₂、AlMg以及Al₂O₃、Al;合金层中铝元素的含量分别为39.7at%和44.5at%;合金层的硬度分别提高至136.0HV和144.98HV;镁合金的耐蚀性得到了提高。通过大量研究,得出了在纯镁和AZ91D合金表面盐浴渗铝的最佳工艺为:350℃、8h。其次,本文研究了表面纳米化对镁合金表面元素扩散的影响。采用超音速微粒轰击纳米化技术（SFPB）对镁合金进行表面处理,使其表层晶粒细化至纳米级;采用盐浴渗铝的方法对表面纳米化镁合金进行元素扩散处理。研究结果表明:SFPB工艺可使镁合金表层晶粒细化至纳米级,将表面纳米化后的镁合金（变形镁合金和AZ91D）进行盐浴渗铝,渗层厚度和耐蚀性均未见明显的改善。更多还原

【Abstract】 Magnesium alloys are the lightest structure meta l in the engineering materia ls. It hasbeen widely applied in the filed of automotive industry, electronic industry,communication, aerospace, nationa l defence and military, etal. It can be recycled veryeasily, so it is called“The green engineering materia ls in the 21st century”. However, itwould be corroded seriously if on protective measures are carried out ahead, because itselectrode potentia l is very low. We can conclude that the poor corrosion resista nce limitsthe applica tion of ma gnesium alloys seriously. At present, it has become a focus todevelop the technics to improve the corrosion resista nce of ma gnesium alloys.The feasibility of salt bath aluminizing on the surface of ma gnesium alloys wasresearched in this paper. Diffution agent used in our experiments was AlCl3&NaCl(1:1).Influnce of the diffution temperature and time on the salt bath aluminizing diffutioncoatings was also researched. The results showed that: it was possible to improve thecorrosion resista nce of ma gnesium alloy with salt bath aluminizing process under presentconditions; a coating with a best thick ness of 15μm and 50μm formed respectively on thesurface of pure ma nisium and AZ91D ma gnesium; the aluminizing la yer was composedwih intermeta llic compound such as Al12Mg17, Al3Mg2, AlMg; there is 44.5 at% and39.7at% aluminium respectively in the intermeta llic la yer of pure ma nesium and AZ91Dma gnesium; the microha rdness of aluminizing on the AZ91D and pure ma nisium andcoatings was 144.98HV and 136.0HV respectively; the corrosion resista nce of ma gesiumalloys was improved; we got the best process parameters : 350℃&8h with a lot of hardwork.Referenced on the research above, the influnce of surface nano-crysta lliza tion on thethermal diffution of ma gnesium alloys was studied in this paper. Supersonic FineParticles Bombarding (SFPB) was used to obtain grains of nanometer dimension on thesurface of wrought ma gnesium and AZ91D ma gnesium. Salt bath aluminizing process was used to treat the ma gnesium alloys afer SFPB. Results showed that: a la yer withgrains of nanometer dimension could be obtained on the surface of wrought ma gnesiumand AZ91D ma gnesium; however, no significa nt improvement of thick ness ofaluminizing coating and corrosion resista nce could be botained after the salt bathaluminizing on the SFPB ma gnesium alloys.更多还原