AZ31镁合金表面等离子喷涂Al65Cu23Fe12涂层的研究

为了改善镁合金的表面性能,采用等离子喷涂方法在AZ31镁合金表面制备一层Al65Cu23Fe12涂层。通过OM、SEM及EDS等分析方法,分析了涂层热处理前后的组织及性能。结果表明:等离子喷涂Al65Cu23Fe12涂层组织主要由-θAl2Cu相、富铝相和富铜相3相组成;经过T4和T6处理后,由于涂层组织发生θ 富Cu→-βAl(Cu,Fe)相转变,涂层的硬度呈增加趋势,由热处理前的200.2 HV增加到304.5 HV,远高于基体AZ31合金的硬度。     

体育器械用AZ31镁合金表面等离子喷涂涂层的组织与性能研究

对体育器械用AZ31镁合金进行等离子喷涂表面处理,对比分析了不同喷涂电流下涂层界面的微观组织和界面结合强度。结果表明,喷涂电流为500 A时,涂层与基体的结合最为致密、均匀,涂层与基体的结合强度最大。     

AZ31镁合金在化学镀镀液中的电化学行为研究

采用混合电位-时间曲线、极化曲线和电化学阻抗谱,研究经不同浓度氢氟酸活化处理后的AZ31变形镁合金在化学镀镀液中的电化学行为,并通过扫描电子显微镜(SEM)观察AZ31活化前后的形貌变化.结果表明,经活化的试样在化学镀过程中被镀层完全覆盖,所用时间随着氢氟酸浓度的增加而延长;镀液中的镍离子被还原的起始电位随着氢氟酸浓度的增加而向正偏移;电极/镀液界面反应的电荷转移电阻随着氢氟酸浓度的增加而增大,并且电极/镀液界面反应是化学镀初始沉积期的控制步骤;AZ31镁合金基体中的Mn-Al相在氢氟酸活化过程中的颗粒脱落是导致氟化膜产生缺陷的主要原因,氢氟酸浓度越高,氟化膜缺陷越少.     

HA粉末粒径对微束等离子喷涂扁平粒子形貌及涂层微结构的影响

目的研究粉末粒径对微束等离子喷涂羟基磷灰石(HA)扁平粒子形貌和涂层的微观组织结构的影响。方法选取三组不同粒径范围(25～38μm、38～45μm、45～63μm)HA球形粉末,采用微束等离子喷涂方法在经镜面抛光的Ti-6Al-4V基体上收集扁平粒子,在经过喷砂处理的Ti-6Al-4V基体上沉积HA涂层。利用冷场发射扫描电子显微镜和X射线衍射仪,对扁平粒子形貌,以及涂层的形貌、相组成和择优取向进行分析。通过激光共聚焦显微镜(LSCM)观察扁平粒子的三维相貌,并对比分析扁平粒子的差异。结果微束等离子喷涂过程中,可形成几种典型形貌特征的扁平粒子,一是中间区域较厚,边缘位置较薄的扁球形;二是中间区域较薄,边缘位置较厚的圆盘状,该种扁平粒子相比于扁球形,其厚度较薄,直径较大;三是边缘位置存在\"指状\"溅射的圆盘状,其厚度与圆盘状扁平粒子厚度相当,但其直径范围较大。HA涂层的结晶度随着粉末粒径的减小而减小,HA的分解和非晶化逐渐增强,涂层的择优取向强度减弱,涂层中柱状晶比例减少。结论微束等离子喷涂过程中,粉末粒径对扁平粒子形貌和涂层相结构有显著影响。随着粒径的增加,扁平粒子由扁球形转变为边缘有少量\"指状\"溅射的圆盘状。粒径较小的HA粉末在等离子焰流中的熔化程度较高,导致涂层中分解相和非晶相含量增多,择优取向程度减小。     

应变速率对AZ31挤压变形镁合金力学行为的影响

通过静态拉伸试验机和高应变速率冲击拉伸试验装置,对AZ31挤压镁合金分别进行了不同应变率下拉伸力学性能的试验,获得了各应变速率下完整的应力-应变曲线。并通过扫描电镜对其拉伸断口进行分析。结果表明,其屈服应力、拉伸强度随着应变速率的增加而增加,失稳应变则随着应变速率的增加而有所减小;而弹性模量则对应变率不敏感。采用Johnson-Cook材料模型描述AZ31镁合金应变速率相关的应力应变本构模型,其拟合结果和实验结果基本相吻合。扫描电镜断口分析结果表明,动态和静态的断裂方式基本相同,都是以准解理断裂特征为主,局部区域伴有解理断裂。     

Sn纳米粒子对AZ31镁合金组织和性能的影响

采用直流电弧等离子体法制备Sn纳米粒子,通过搅拌铸造的方法添加到AZ31镁合金当中。通过金相、扫描电镜和拉伸性能测试等技术,考察了添加不同量的Sn纳米粒子对AZ31镁合金铸态组织和力学性能的影响。结果表明,添加Sn纳米粒子可抑制共晶相以层片状析出,促进β-Mg_(17)Al_(12)相以骨骼状分布在晶界处。重要的是,观察到Sn纳米粒子在镁合金中生成了纳米尺寸的Mg_2Sn颗粒,但主要以颗粒团簇的形式存在。过量添加Sn纳米粒子,会使Mg2Sn纳米级颗粒团聚严重,降低AZ31镁合金的力学性能。结果表明,添加1%Sn(质量分数)纳米粒子,AZ31镁合金的力学性能最优。     

钇离子注入AZ31镁合金的氧化行为

研究了AZ31镁合金在钇离子剂量为5×10^16，1×10^17及5×10^17ions／cm^2注入条件下的氧化性能。纯氧气氛、500℃下的氧化实验结果表明，钇离子注入能提高AZ31镁合金的抗氧化性能，而且随着注入剂量的增大，合金表面抗氧化性能提高越大。俄歇电子能谱（AES）和X光电子能谱（XPS）分析表明：钇离子注入以后，在镁合金表面形成了具有双层结构的氧化层，外层主要由MgO组成，而内层主要由Y2O3，MgO构成。这一新形成的氧化层有利于提高AZ31镁合金的抗氧化性能。     

镁合金AZ31轧制板材的单向拉伸行为

通过单向拉伸试验研究了AZ31镁合金轧制板在不同温度和应变速率下的力学性能。根据镁合金在50℃~400℃范围内的单向拉伸曲线分析结果,找出AZ31镁合金的抗拉强度、伸长率随变形温度、变形速度的变化规律。结果表明:AZ31镁合金轧制板的塑性随着应变速率的降低有明显提高;温度的升高可明显改善轧制板的塑性;当应变速率为1.5×10-2s-1、温度为400℃时,伸长率达到123.9%。     

汽车用AZ31镁合金的高周疲劳行为研究

研究了挤压态AZ31镁合金的高周疲劳性能。结果表明,采用升降法算出其在R=0.1、Nf=107时的疲劳极限为96.8 MPa,疲劳寿命随着应力的增加而快速降低;拉伸形变能降低其疲劳寿命;疲劳断裂为解理断裂。     

Environmentally assisted cracking behaviour of plasma electrolytic oxidation coated AZ31 magnesium alloy

Abstract

A wrought AZ31 magnesium alloy was plasma electrolytic oxidation (PEO) coated in phosphate and silicate based alkaline electrolytes. The effect of these PEO coatings on the stress corrosion cracking (SCC) behaviour of the alloy was investigated by slow strain rate tensile (SSRT) tests in ASTM D1384 solution. The untreated and PEO coated AZ31 magnesium alloy specimens were found to be susceptible to SCC, despite the fact that the PEO coatings offered an excellent general corrosion resistance. The results of the polarisation tests on the untreated AZ31 alloy specimen after prolonged immersion in ASTM D1384 electrolyte suggested the formation of a film on the surface constituted by the corrosion products. The cracking of this film and the evolution/ingress of hydrogen at these defective sites during the SSRT tests in the corrosive environment was believed to be responsible for the SCC of the untreated alloy. Similarly, the cracking of the PEO coatings during the SSRT test, the consequent exposure of the underneath magnesium alloy substrate and the associated electrochemical reactions were attributed as reasons for the SCC of the PEO coated specimens. The transgranular mode of fracture in all the cases avowed that the hydrogen induced cracking was the mechanism of SCC.     

AZ31镁合金钕基转化膜研究

通过化学转化成膜在AZ31镁合金表面制备了钕基转化膜。利用称重实验和OCP测试研究了钕基转化膜的成膜过程,利用SEM,EDS和XPS分别研究了膜层形貌,微观结构和组成成分。研究了空白样品与镀膜样品在3.5 wt.% NaCl 溶液中浸泡不同时间后样品表面形貌和成分,结果表明钕基转化膜可以有效的降低AZ31镁合金在NaCl溶液中的腐蚀速率。利用XRD和电化学测试研究了经过后处理以后的钕基转化膜的成分和耐蚀性能,结果说明后处理可以进一步改善钕基转化膜的腐蚀性能。     

AZ31镁合金铝涂层机械研磨振动热扩散研究

以AZ31镁合金热喷涂铝涂层为研究对象,用自制的振动热扩散装置,进行一定温度热扩散或在热扩散的同时进行振动机械研磨处理,研究比较了振动热扩散对镁合金热喷铝涂层的影响.采用金相显微镜、扫描电子显微镜观察涂层表面、截面形貌,对涂层界面进行能谱分析,利用显微硬度计测量不同工艺下涂层与镁基体界面处硬度变化,利用X射线衍射分析涂层与基体界面处扩散区域相组成,用电化学工作站测得涂层极化曲线,通过盐水浸泡分析比较了不同工艺处理后镁合金的耐腐蚀性.结果表明:镁合金喷铝涂层经360～400℃保温2h热扩散或振动热扩散(机械研磨热扩散),在涂层与镁基体的界面处镁铝原子有不同程度的互扩散,并有镁铝Al12Mg17相生成,界面硬度有极大提高,振动热扩散使涂层明显致密化并形成连续析出相,能有效提高涂层的耐腐蚀性能.     

AZ31镁基高速火焰喷涂WC涂层的研究

材料的轻量化已经越来越成为一种趋势.镁合金因为更高的比强而作为铝合金的替代材料,在机械、电子和航空等工业有着广泛的应用前景.然而镁合金因硬度低,抗腐蚀性差而使应用受限制,因此需要进行表面处理以提高材料的使用寿命和拓宽应用领域.采用High-Velocity-Air-Fuel(高速火焰喷涂)技术在AZ31镁合金基体上制备了WC-CoCr涂层,采用XRD、SEM分别对涂层的相和显微结构进行了分析,同时研究了拉伸对偶件的弹性模量对涂层结合强度测试的影响,重点阐述了涂层的结合机理.此外,还研究了镁基高速火焰喷涂WC涂层的抗中性盐雾腐蚀性能.结果表明,采用HVAF技术,可在AZ31镁合金基体上获得致密,结合强度较高且具有良好抗腐蚀性能的WC-CoCr涂层.     

AZ31镁合金表面碱性化学镀镍工艺研究

试验研究了AZ31镁合金表面碱性化学镀镍工艺。采用扫描电镜(SEM)、能谱成分分析(EDS)和X射线衍射(XRD)等方法对镀镍层的表面形貌、镀层成分及物相结构进行了分析,并测定了AZ31镁合金及镀层在w(NaCl)=3.5%的水溶液中的腐蚀电位和极化曲线,以此评价镀层的耐腐蚀性能。结果表明,预镀镍层为晶格畸变的晶态低磷镀层,二次镀镍层为非晶态高磷镀层,镁合金表面腐蚀电位在化学镀镍后明显升高,二次镀镍后钝化电位范围明显扩大,其耐腐蚀性能明显优于预镀镍层的。     

AZ31B镁合金及其纳米复合材料的滑动磨损行为(英文)

采用复合铸造工艺制备AZ31B镁合金及其纳米复合材料,再对所得材料在350°C进行热挤压。采用标准的销-盘式摩擦磨损试验机对AZ31B镁合金及其纳米复合材料的室温滑动磨损行为进行研究。实验条件为法向载荷10N、滑移速度0.60~1.2m/s、滑移距离2000m。采用SEM观察来研究磨损表面的磨损机理。通过构建一个线性回归模型来研究试验参数对磨销磨损率的影响。与AZ31B镁合金相比,由于增强体的作用而导致的硬度增强使复合材料表现出低的磨损率。犁削、犁沟、分层和氧化构成混合的磨损机理。     

Investigation of particle flattening behaviour and bonding mechanisms of APS sprayed coatings on magnesium alloys

Magnesium alloys are promising alternatives to other lightweight materials due to their high specific strength and stiffness. However, the use of magnesium alloys is limited by their poor wear behaviour and low corrosion resistance for many industrial applications. The thermal spray technology offers a wide range of possibilities to improve the surface properties of Mg-based components. In this study, three different coating materials, namely Al, NiAl5 and Al₂O₃, were applied on AZ91 and AE42 substrates using the atmospheric plasma spray technology. The investigation was focused on the bonding strength of the coatings and the related bonding mechanisms. For a better understanding of the bonding mechanisms, the flattening behaviour of the spray particles was investigated in correlation with the substrate pre-heating temperature. It was found that NiAl5-particles could well melt the substrate at the surface and deformed it locally; Al-particles did the same but to a lower extent. The dominating bonding mechanism for NiAl5-coatings could be attributed to a metallurgical bonding. For Al-coatings, this mechanism played a more important role once the substrate pre-heating temperature was increased. Al₂O₃ particles in contrast, were less able to deform the substrate in spite of their higher thermal load and the mechanical anchoring remained the main bonding mechanism. The thermo physical properties of the Mg substrate showed also to have an influence on the adhesion of the coatings.     

Anticorrosive magnesium phosphate coating on AZ31 magnesium alloy

A novel anticorrosive film with a thickness of approximately 50 μm was successfully coated on an AZ31 magnesium alloy by chemical and low-heat treatments (50 °C). The film was a single-phase system of newberyite (MgHPO₄•3H₂O) having an orthorhombic crystal structure. The corrosion current density of the newberyite film coated on the AZ31 magnesium alloy decreased by more than two orders of magnitude as compared to that of the AZ31 magnesium alloy. The static water contact angle of the newberyite film was less than 10°. The average value of the scratch critical load for the newberyite coating was estimated to be approximately 15 mN.     

Influence of silane on corrosion resistance of magnesium alloy AZ31 with thermally sprayed aluminum coatings

Aluminum coatings on Mg alloy AZ31 were fabricated using the thermal spraying technique, and then sealed with silane.The surface morphology and chemical groups were discerned using scanning electron microscopy and examined using Fourier transformation infrared spectroscopy, respectively.The salt fog tests and the potentiodynamic electrochemical technique were applied to evaluate the influence of silane on corrosion of the AZ31 alloy with aluminum coatings.The results showed that the corrosion resistance of ...