摘 要
铸造Al-Si系合金具有质量轻、比强度高和加工性能好等优点，是铸造铝合金中应用最多的合金系。但其表面硬度低、耐磨性能较差，使其应用受到制约，采用微弧氧化技术可在合金表面原位生成陶瓷膜，有望提高其表面的硬度、耐磨性及耐蚀性等性能，扩大其应用范围。就现有的研究成果看，电解液组成对微弧氧化过程及陶瓷层的影响机理非常复杂，目前尚无统一、明确的认识。因此，针对电解液组成的研究仍有许多工作要做。
本文采用WHD-30多功能微弧氧化设备对ZAlSi12进行微弧氧化。试验过程中电压值保持恒定，正负向工作电压分别为420V和120V，频率为100Hz，氧化时间固定为20min，在微弧氧化过程中电流自动调节变化。根据前期试验确定基础电解液组成为8.0 g/L Na2SiO3 +2.0 g/L NaOH +2.0 g/L EDTA，在基础电解液中分别加入适量的Ce(NO3)3、、La(NO3)3、Ce(SO4)2和Na5P3O10等添加剂，研究添加剂种类及含量变化时，所得微弧氧化陶瓷膜特性变化规律，采用涡流测厚仪、SEM、XRD、EDS等分析手段对微弧氧化陶瓷层进行了表征。
交换机英文结果表明：电解液中加入Ce(NO3)3后，陶瓷氧化层厚度增大，最大厚度为170μm，所获得的膜层仍主要由α-Al2O3和γ-Al2O3相组成，但α-Al2O3相的相对含量增加；加入La(NO3)3后，膜层增厚，最大值为146μm，能谱分析显示La 元素也进入到膜层中，说明电解液中La(NO3)3影响了氧化过程及微弧氧化膜
的特性；研究发现，在基础电解液8.0 g/L Na2SiO3 +2.0 g/L NaOH +2.0 g/L EDTA中加入Ce(SO4)2添加剂后，试样表面形成的氧化膜更加平整、致密，膜层表面质量有所改善；在基础电解液中加入Na5P3O10可对电解液起到螯合作用，防止沉淀产生，提高电解液利用率，从而使放电时间延长，膜层质量大大改善。
关键词：微弧氧化；ZAlSi12；稀土盐复合电解液；陶瓷膜；表征
Abstract
Cast aluminum alloys are wide applied in industry field due to its low density ,high specific strength and excellent processing properties.However, the poor wear resistance which has restricted the application of unprotected aluminum alloys, Micro-arc Oxidation is an effective and promising surface treat technique ,by using MAO method ,the film which situ-growed on the substrate can obtained . Conquently ,the hardness, wear resistance and corrosion resistance of the alloy was improved. The mechanism that the electrolyte have on the MAO process and characterization of ceramic coating were very complexes until now ,it hasn’t made an unique and definite cognition ,so there have many work to do to study the composition of electrolyte .
汽车发动机维修
The ceramic coating were prepared on the surface of ZAlSi12 alloys and a high power supply unit (
WHD-30) treatment device was adopted for MAO process ,the potentiostatic method was adopted in this work ,the applied positive/negative potential of the acyclic was 420/120V respectively, predefined frequency at 100HZ,current density variated with the automatic adjustment ,an aqueous alkaline electrolyte of Na2SiO3 8.0 g/L+ NaOH 2.0 g/L + EDTA 2.0 g/L was formulated, an appropriate amount of additive Ce(NO3)3、La(NO3)3、Ce(SO4)2·4H2O及Na5P3O10 were added into Na2SiO3 -NaOH (alkali-silicate)electrolytic system. The regularity that the effect of additive concentration and have on the characterizations of coating were investigated ,the coatings were characterized by eddy current thickness meter,SEM,XRDand EDS analysis methods .the result show that :the thickness of ceramic coating incread after added Ce(NO3)3 into electrolyte and the max value reach to 170μm,the coatings formed in the electrolyte contained Ce(NO3)3 are still compod by α-Al2O3 pha and γ-Al2O3 pha ,but the proportion of α-Al2O3 pha incread after added Ce(NO3)3 into electrolyte ;the thickness of the coating incread with the content of La(NO3)3 incread in the electrolyte ,and the max value reach to 146μm,it is also found by EDS that there was La element in ceramic coating. This indicates that La(NO3)3 contained in electrolyte has an effect on the process of oxidation and characteristics of micro-arc oxidation coatings. It can also established that ,the improved induced mass of films were obtained after add Ce(SO4)2 into Na2SiO3 –NaOH system electrolyte ,a uniform, compacted and barrier coating can be formed on the surface of
ZAlSi12 alloy, the Na5P3O10 additive have an effect of chelating which can improve the utilization ratio of electrolyte and avoid generation of deposition, accordingly the discharge time was extended and the properties of coatings were anticipated to improved.文化艺术策划
Key words: Microarc oxidation；ZAlSi12；Composite electrolyte with rare-earth salts；
ceramic coating ；characterization
目 录
第一章绪论 (1)
1.1 选题背景 (1)
1.2 选题的目的及意义 (5)
1.3 国内外研究概况 (6)
1.3.1 微弧氧化技术的基本原理 (6)
1.3.2 微弧氧化技术特点 (8)
1.3.3 微弧氧化技术的发展历史 (9)
1.3.4 微弧氧化技术发展现状 (10)
1.3.5 微弧氧化技术的应用前景和发展趋势 (13)
1.4 本课题的主要研究目的及研究内容 (15)
竞选宣言
故宫景点介绍1.5 试验方案设计 (15)
第二章试验方法及过程 (17)
怎样哄女孩子
2.1试验材料 (17)
2.1.1基体材料 (17)
2.1.2电解液组成 (17)
2.2试验设备 (17)
2.3试验中所用电解液体系 (18)
2.4 试验内容 (20)
2.5 陶瓷膜特性测试过程 (21)
第三章试验结果与分析 (23)
3.1 NaOH + Na2SiO3 + Ce(NO3)3电解液体系中所得陶瓷层的表征 (23)
3.1.1陶瓷层厚度 (23)
3.1.2陶瓷层表面形貌 (24)
3.1.3陶瓷层相组成 (25)
3.1.4 能谱分析 (27)
3.2 NaOH + Na2SiO3 + La(NO3)3电解液体系中所得陶瓷层表征 (28)
3.2.1陶瓷层厚度 (28)
法治进校园3.2.2 陶瓷层表面形貌 (29)
3.2.3陶瓷层相组成 (31)
3.2.4 能谱分析 (33)
同事结婚祝福
3.3 NaOH + Na2SiO3+ Ce(SO4)2电解液体系所得陶瓷层表征 (34)
3.3.1 陶瓷层厚度 (34)
3.3.2陶瓷层表面形貌 (35)
3.3.3 陶瓷层相组成 (37)
3.3.4能谱分析 (38)
3.4 NaOH + Na2SiO3 + Ce(SO4)2 + Na5P3O10电解液体系所得陶瓷层表征 (39)
3.4.1陶瓷层厚度 (39)
3.4.2陶瓷层表面形貌 (41)
3.4.3 陶瓷层相组成 (43)
3.4.4能谱分析 (45)
第四章微弧氧化过程及膜层生长机理探讨 (47)
4.1等离子体的概念 (47)
4.2微弧氧化膜的击穿原理 (48)
4.3微弧氧化过程 (49)
4.4电解液中稀土元素在微弧氧化过程中的作用 (52)
4.5电解液中加入Na5P3O10对陶瓷层形成过程的作用 (54)
第五章结论 (55)
参考文献 (57)
致谢 (63)
攻读硕士学位期间发表的学术论文 (64)
个人简介 (65)
