AZ31和稀土镁合金微弧氧化膜的对比研究

在相同的工艺参数下制备了AZ31和Mg 10Gd 2Y-0.4Zr稀土镁合金微弧氧化膜层.利用SEM、XRD和EDS对两种陶瓷膜层的组成、微观形貌和元素组成进行了表征;通过电化学测试和盐雾试验评价了两种陶瓷膜层的耐蚀性能;利用显微硬度仪研究了两种陶瓷膜的显微硬度.结果表明:两种陶瓷层的厚度、表面形貌和致密性相似;陶瓷膜由MgO和Mg2SiO4组成,其中MgO为主晶相;与AZ31镁合金陶瓷膜相比,稀土镁合金陶瓷膜中的MgO含量增多,Mg2SiO4含量减少;两种镁合金表面陶瓷化后的耐蚀性和硬度大大提高,AZ31镁合金陶瓷膜耐蚀性优于稀土镁合金陶瓷膜,稀土镁合金陶瓷膜的硬度高于AZ31镁合金陶瓷膜.     

纳米SiC陶瓷颗粒增强复合材料层的制备及性能研究

采用脉冲钨极氩弧表面熔敷工艺在镁合金AZ31板材表面制备了纳米SiC陶瓷颗粒和铝粉增强表面复合材料层,该工艺是一种有效制备高性能表面复合材料层的方法.复合材料层内部获得显著细化的晶粒,而且纳米SiC陶瓷颗粒分布均匀.AZ31母材的硬度只有55HV左右,而复合材料层的硬度达到155HV,其耐磨性和耐腐蚀性能均优于镁合金AZ31母材.     

AZ31B镁合金TIG焊接件应力腐蚀性能研究

为了研究AZ31B镁合金钨极氩弧焊接件应力腐蚀性能,室温下采用三点加载的方式,在去离子水中对试样进行应力腐蚀试验。利用光学显微镜(OM)观测试样微观结构,利用扫描电镜(SEM)观测应力腐蚀断口,利用X-350A型X射线应力仪和CHI660B型电化学工作站分别测定试样表面残余应力和动电位极化曲线。试验结果表明:采用单面焊双面成型工艺,在45～50A的焊接电流及合适的焊接速度条件下,焊接2.2mm厚AZ31B镁合金薄板时,钨极氩弧焊能够获得理想的焊接接头,抗拉强度达到209MPa;焊接件热影响区表面残余拉应力为60MPa;同母材相比,焊接件自腐蚀电位减小27mV,腐蚀电流增大了41.4%,从而增加焊接件腐蚀倾向;AZ31B焊接件在去离子水中浸没192h后出现应力腐蚀开裂,属于穿晶型脆性断裂,这表明AZ31B镁合金焊接件在去离子水中具有很高的应力腐蚀敏感性。     

激光冲击处理对AZ31B镁合金力学性能的影响

为了研究激光冲击处理对AZ31B镁合金力学性能的影响,采用波长为1054nm,脉冲宽度为15ns,脉冲能量为10J,光斑直径为3mm的YAG脉冲激光,对变形镁合金AZ31B薄板试样表面进行冲击处理。结果表明:根据优化的工艺参数,激光冲击处理能在AZ31B镁合金上制备出纳米结构表层,表面晶粒尺寸约为20nm;试样表面激光诱导的残余压应力高达-125MPa;激光冲击处理试样的抗拉强度提高了16.9%;屈服强度提高了16.3%;表面硬度提高了91.8%。利用透射电镜(TEM)、扫描电镜(SEM)观测激光冲击试样微观结构,并分析了力学性能提高的机理。     

AZ91镁合金表面等离子熔凝处理及耐蚀性研究EI北大核心

通过AZ91镁合金表面等离子处理,获得了镁合金表面熔凝层组织,采用SEM,EDS,极化曲线等测试方法,对处理后的AZ91镁合金微观结构和耐腐蚀性进行了研究,讨论了不同电流对AZ91镁合金硬度及熔凝层深度的影响。结果表明:经等离子扫描处理后的镁合金晶粒明显细化,硬度值显著提高,自腐蚀电位增大,自腐蚀电流密度减小,耐腐蚀性得到提高。     

AZ91D镁合金电偶腐蚀的扫描开尔文探针原位表征

AZ91D镁合金在潮湿、含C1-大气环境中会发生严重的电偶腐蚀.对AZ91D镁合金与Q235碳钢偶接试样在中性盐雾条件下进行了电偶腐蚀试验,利用扫描开尔文探针技术(SKP)原位测量了不同盐雾试验时间后两偶合件表面伏打电位的变化规律.结果表明:由于AZ91D镁合金与Q235碳钢偶接试样存在较大的伏打电位差(约为-1.14...     

塑性变形对铸态AZ31镁合金组织和性能的影响

为了研究塑性变形对铸态镁合金组织和性能的改善作用,用铸态AZ31镁合金进行了等温压缩实验,并测试了原始试样和变形后试样的组织和性能.结果表明:铸态AZ31合金通过塑性变形可以显著细化晶粒;随变形温度的升高,变形所得试样抗拉强度下降;在同一温度下变形所得试样抗拉强度随变形程度的增加而升高,变形程度达到一定值后,抗拉强度不再升高并有下降的趋势;铸态AZ31合金低温变形(210～240℃)后,可大幅度提高其抗拉强度.     

镁合金AZ91D焊接组织及腐蚀行为研究

利用钨极氩弧焊(TIG)、光学显微镜和盐雾腐蚀实验以及电化学测试技术,研究了镁合金AZ91D焊接对焊缝组织及其耐蚀性的影响.实验表明:镁合金AZ91D焊缝组织为比母材晶粒细小的等轴晶粒,提高了焊缝区硬度.焊缝区耐蚀性较母材好,其腐蚀速度与热影响区接近,比母材低1倍.     

AZ31镁合金表面多层膜的结构与性能研究

研究了在AZ31镁合金表面依次进行浸锌、化学镀镍、电镀铜、电弧离子镀Cr/CrN的复合镀膜工艺.利用x射线晶体分析仪、扫描电镜、显微硬度计、腐蚀测量系统及热震法等仪器和方法对复合镀层的显微组织及性能进行了研究.结果表明,在此复合镀工艺条件下,可以在AZ31镁合金表面形成致密度高、结合强度好、耐蚀性好且硬度高的复合合金镀层;AZ31镁合金镀膜后的显微硬度形成一个梯度,由71.1HK提高到2224.8HK;耐蚀性明显提高,腐蚀电位从-1481mV提高到-382mV.     

AZ91D镁合金表面熔盐置换扩散涂层组织及耐腐蚀性能研究

采用AlCl3-NaCl熔盐自发置换扩散工艺在AZ91D镁合金表面制备镁铝金属间化合物涂层,并利用开路电位、电化学阻抗方法对镁合金及熔盐置换扩散改性处理试样在3.5%(质量分数)NaCl溶液中的腐蚀行为进行比较研究。结果表明:熔盐自发置换扩散铝涂层在温度为400℃,保温8h的工艺条件下呈现出了明显的分层结构特征。根据组织结构不同,可将其分为:颗粒状形貌的外层和具有网状结构的内层;经表面熔盐自发置换扩散处理后的镁合金试样,腐蚀电位比未改性的AZ91D镁合金大幅提高,膜层阻抗约为未改性的AZ91D镁合金的10倍。     

The properties of gas tungsten arc deposited SiCP and Al surface coating on magnesium alloy AZ31

SiC particles and aluminum powders were used to deposit on the surface of magnesium alloy AZ31 by pulse square-wave alternating current gas tungsten arc (GTA) processing. This method is an effective technique in producing a high performance surface modified composite layer. The microstructure, microhardness, wear resistance and corrosion behavior of the GTA surface modified composite layer were evaluated. It was proved that no reaction products were formed at the SiC-matrix interface and no melting or dissolution of the SiC particle occurred during GTA surface modification. The microhardness of GTA surface modified composite layer was between 100 and 150 HV according to the variation of the GTA processing parameters. The microhardness, wear resistance and corrosion behavior of the GTA surface modified layer were superior to that of the as-received AZ31. The optimum processing parameters of the GTA surface modification of magnesium alloy AZ31 with SiC + Al for the formation of a homogeneous crack/defect-free and grain refinement microstructure were established.     

AZ31镁合金的SiO2（Mg）涂层的组织及性能研究

采用机械合金化的方法在AZ31镁合金表面涂覆SiO₂（Mg）涂层。通过XRD、显微硬度计、扫描电镜等测试手段对表面涂层的微观形貌结构、涂层的显微硬度进行分析,利用电化学工作站对涂覆前后的AZ31镁合金的耐蚀性能进行检测。结果表明:SiO₂涂层被成功地涂覆到AZ31镁合金表面;同时,随着球磨时间的增加,涂层的显微硬度呈增加趋势,且随着球料比的增加,显微硬度亦增加,最高达到370.6HV,较基体提高了15.2%;涂层的厚度也呈现先增加后趋于稳定的趋势,但球磨时间过长,涂层内部出现裂纹;当球料比为15:1、球磨时间为15 h时,所制备涂层厚度为148μm,涂层致密且与基体结合较好;所对应的自腐蚀电流密度较基体降低了一个数量级,对应的腐蚀电压提高了6.5%,耐腐蚀性能得到明显改善。      

退火处理对AZ31镁合金表面Ni-Mo-P镀层组织与耐腐蚀性能的影响

为了进一步提高镁合金表面Ni-Mo-P镀层的耐蚀性,采用0M、XRD和浸泡试验等方法,研究了退火处理对AZ31镁合金表面Ni-Mo-P镀层组织与腐蚀性能的影响。结果表明:AZ31镁合金阳极氧化-化学镀Ni-Mo-P镀层表面为“胞状”组织,随着退火温度的升高或退火时间的延长,AZ31镁合金阳极氧化-化学镀Ni-Mo-P镀层的胞状组织逐渐细化,但镀层厚度降低,同时,非晶态Ni-Mo-P镀层组织逐渐向晶态转变,350℃退火1.0h具有较高的非晶化程度,退火处理后的Ni-Mo-P镀层由Mg、MgO、Mg2SiO4、Ni和Ni3P组成;退火使AZ31镁合金阳极氧化-化学镀Ni-Mo-P镀层耐蚀性降低,350℃退火1.0 h镀层具有相对较好的耐蚀性,这与镀层的厚度和非晶化程度有关。     

复合喷丸提高等轴状TC4钛合金的疲劳性能

首先对等轴状TC4钛合金疲劳试样表面进行了不同时间的高能喷丸,制备出一定深度的纳米表层,然后采用小尺寸弹丸进行表面损伤修复喷丸,提高纳米表层质量,最后对不同喷丸状态的试样进行了疲劳试验。结果表明:复合喷丸使等轴状TC4钛合金的疲劳强度相比未喷丸状态提高了34%,在单纯高能喷丸纳米化方法的基础上进一步提高了12%;高能喷丸在试样表面形成的损伤阻碍了表层纳米化提高疲劳强度的效果,通过修复喷丸可以修复部分高能喷丸损伤。     

AZ31镁合金酸性化学镀Ni-Co-P层的耐腐蚀性能

为了提高镁合金的耐蚀性,以酸性化学镀的方法在AZ31镁合金表面制备了Ni-Co-P镀层。分别用XRD,SEM和EDS对镀层的结构、表面形貌和成分进行了分析,并用点滴试验和电化学方法测试了镀层的耐蚀性。结果表明:酸性化学镀Ni-Co-P层为非晶态胞状结构,镀层中P含量可高达9.41%,远高于碱性镀层;AZ31镁合金镀覆Ni-Co-P合金层后腐蚀电流比基体降低3个数量级,其耐蚀性能显著提高。     

Polishing-assisted galvanic corrosion in the dissimilar friction stir welded joint of AZ31 magnesium alloy to 2024 aluminum alloy

Galvanic corrosion of a dissimilar friction stir welded 2024-T3 Al/AZ31B-H24 Mg joint prepared using a water-based and a non-water-based polishing solution was characterized. Microstructure and the distribution of chemical elements were analyzed using optical microscopy, scanning electron microscopy and energy dispersive X-ray spectroscopy. The stir zone polished using water-based solution was observed to be much more susceptible to galvanic corrosion attack than that obtained using non-water-based polishing solution. The location of corrosion attack was observed in the narrow regions of AZ31 Mg alloy adjacent to Al2024 regions in the stir zone. The occurrence of galvanic corrosion was due to the formation of Mg/Al galvanic couples with a small ratio of anode-to-cathode surface area. The corrosion product was primarily the porous magnesium hydroxide with characteristic microcracks and exhibited a low microhardness value.     

AZ31镁合金表面气相沉积不锈钢薄膜的实验研究

利用真空蒸发镀膜技术在镁合金表面沉积不锈钢薄膜是提高镁合金防腐性能的新尝试.本研究利用该技术在AZ31上成功制备了不锈钢薄膜.通过在5%NaCl溶液中的浸入实验和极化实验考察了腐蚀性能,发现镀膜后耐蚀性显著降低.另外,镀膜后的显微硬度也未有明显提高.利用AFM,SEM,EDX等分析手段对薄膜进行了观察和检测,发现耐蚀性变差的原因主要是薄膜表面存在贯穿性的微米级孔洞和Cr元素分布不均匀造成的.     

Corrosion behavior of friction stir welded AZ31B magnesium alloy with plasma electrolytic oxidation coating formed in silicate electrolyte

A protective ceramic coating of about 50 μm thick on a friction stir welded (FSW) joint of AZ31B magnesium alloy was prepared by plasma electrolytic oxidation (PEO) in silicate electrolyte. Electrochemical corrosion behavior of uncoated and coated FSW joints was evaluated by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The equivalent circuits of EIS plots for uncoated and coated FSW magnesium alloy were suggested. The corrosion resistance of FSW magnesium alloy depended on microstructure of the FSW joint. The heat-affected zone with severe grain growth was more susceptible to corrosion than the stir zone and base metal. The PEO coating consisted of a porous outer layer and a dense inner layer. The inner layer of PEO coating played a key role on corrosion protection of the FSW joint of magnesium alloy. Meanwhile, corrosion potential, corrosion current density and impedance at different zones of coated FSW joint were almost the same. The PEO surface treatment significantly improved the corrosion resistance of FSW joints of AZ31B magnesium alloy.     

Growth and corrosion of aluminum PVD-coating on AZ31 magnesium alloy

Magnetron sputtering was applied to prepare aluminum coating on a mechanically polished AZ31 magnesium alloy. A loose oxide film was spontaneously formed on the surface of AZ31 magnesium alloy during polishing process. The aluminum coating, which was subsequently deposited on this oxide layer, presented a developed columnar microstructure. Attributed to the barrier effect of Al coating, the Al coated AZ31 showed a higher corrosion resistance than bare AZ31 in corrosion tests. Generally, Al coating is cathodically protected by magnesium alloy substrate. But it is interesting in this study that Al coating still suffered from severe corrosion due to the occurrence of the alkalization effect.     

表面渗铝改性镁合金的轧制组织性能

引入"固态扩渗+轧制"一种新的表面改性方式,在研究镁合金薄板表面改性方法及工艺的基础上,采用固态扩渗的方法对AZ31镁合金薄板进行表面渗铝改性处理获得Al/AZ31镁基复合材料;借助有限元软件LS-DYNA模拟其冷轧过程,获得最优轧制工艺条件并进行轧制试验,通过XRD、SEM、金相显微镜、布氏硬度测量计、往复式摩擦磨损试验机和CorrTest腐蚀电化学测试系统检测材料表面的组织性能。结果表明:Al/AZ31镁基复合材料轧制变形后表面形变强化使表面组织晶粒更加细小、均匀,同时产生新的物相MgAl2O4,使其耐磨耐腐蚀性得到改善,表面布氏硬度从HB61.4提高到HB63.5,摩擦因数由0.52提高为0.60,表面摩擦磨损质量损失从0.33mg减小到0.26mg;表面耐腐蚀性能显著提高,自腐蚀电位从-1.49V提高为-1.38V,自腐蚀电流密度从6.2×10-3 mA/cm2降为7.0×10-4 mA/cm2。采用"固态扩渗+轧制"的方法获得的Al/AZ31镁基复合材料的耐磨性有所改善,耐腐蚀性能显著提高。