扩渗温度和时间对镁合金表面Al-Zn共渗层显微组织的影响

    采用扩渗法在镁合金表面共渗Al-Zn,研究了扩渗时间和温度对表面合金层显微组织的影响.结果表明：当温度为390℃时,随着扩渗时间的增加,生成的表面合金层由不连续金属间化合物层(Al6Mg10Zn、Al5Mg11Zn4)＋过渡层变为连续金属间化合物层+过渡层;此过程应是物理置换扩散机制和反应扩散机制同时存在,生成的金属间化合物相主要为Al6Mg10Zn和Al5Mg11Zn4两种类型金属间化合物,其中Al5Mg11Zn4是较为稳定的相;当温度提高到410℃时,晶界扩散活性提高,晶界扩散通道增强,仅为2小时已出现了严重的沿晶界扩渗,造成合金层中金属间化合物沿晶界呈网状不均匀分布.     

大气下纯镁表面扩散锌钇渗层组织和性能

大气下采用固态扩散锌钇共渗的方法,在390℃对纯镁进行表面合金化改性处理。采用OM、SEM、EDS、XRD和显微硬度、电化学腐蚀极化曲线测试等方法分析渗层的组织结构、显微硬度和耐蚀性能。结果表明,经表面合金化处理,在纯镁表面获得了致密的渗层,厚约900μm。渗层由过渡层和合金反应层两部分组成,过渡层是α-Mg固溶体,合金反应层由大量的Mg7Zn3和α-Mg固溶体及α-Mg和MgZn片层状共晶组织组成,材料表层的显微硬度有很大提高,平均硬度约为纯镁的4倍,自腐蚀电位比纯镁正移87mV,自腐蚀电流密度降低了约1个数量级,耐腐蚀性能明显改善。     

Effects of annealing heat treatment on the corrosion resistance of Zn/Mg/Zn multilayer coatings

Zn coatings alloyed with magnesium offer superior corrosion resistance compared to pure Zn or other Zn-based alloy coatings. In this study, Zn/Mg/Zn multilayer coatings with various Mg layer thicknesses were synthesized using an unbalanced magnetron sputtering process and were annealed to form Zn-Mg intermetallic phases. The effects of the annealing heat treatment on the corrosion resistance of the Zn/Mg/Zn multilayer coatings were evaluated using electrochemical measurements. The extensive diffusion of magnesium species into the upper and lower zinc layer from the magnesium layer in the middle of the coating was observed after the heat treatment. This phenomenon caused (a) the porous microstructure to transition into a dense structure and (b) the formation of a MgZn₂ intermetallic phase. The results of the electrochemical measurements demonstrated that the heat treated Zn/Mg/Zn multilayer coatings possessed higher levels of corrosion resistance than the non-heat treated coatings. A Zn/Mg/Zn multilayer coating with MgZn₂ and (Zn) phases showed the best corrosion resistance among the heat treated coatings, which could be attributed to the reduced galvanic corrosion effects due to a small potential gradient between the MgZn₂ and zinc.     

退火处理对Al/ZE42/Al复合板界面组织和腐蚀行为的影响

采用光学显微镜、扫描电镜、盐水浸泡等方法研究了退火热处理工艺对Al/ZE42/Al复合板界面微观组织和该复合板在5.0%Na Cl(质量分数)水溶液中腐蚀行为的影响。实验结果表明:Al/ZE42/Al复合板经退火处理后,界面区域发生Mg和Al等元素的互扩散,界面扩散层包含2个反应层,靠近ZE42镁合金一侧的反应层为Mg_(17)Al_(12)相,靠近Al板一侧的反应层为Al_3Mg_2相,随着退火温度的升高或者保温时间的延长,ZE42/Al界面扩散层的厚度增加,ZE42镁合金发生了再结晶组织转变;退火热处理没有明显改善Al/ZE42/Al复合板的耐腐蚀性能,提高了腐蚀速率,其腐蚀机制为复合板边部向内部扩散而导致的电偶腐蚀加剧。     

The effect of solid diffusion surface alloying on properties of ZM5 magnesium alloy

In this research, solid diffusion process was used to form a diffusion alloying layer on the surface of ZM5 magnesium alloy to improve corrosion and wear resistance. It is shown that the solid diffusion layer was mainly composed of Mg–Al–Zn intermetallic compounds and Mg–Al–Zn solid solution transition zone that had more Zn and Al elements than untreated ZM5 magnesium substrate. The continued immersion test in 3% NaCl solution displayed that the diffusion-treated specimen had better corrosion resistance compared to the untreated ZM5 specimen. The polarization test indicated that the Mg–Al–Zn intermetallic compounds of the diffusion alloying layer were an effective corrosion barrier to decrease the corrosion rate for ZM5 magnesium alloy when exposed to 3% NaCl solutions. In addition, the microhardness values of the Mg–Al–Zn intermetallic compounds were much higher than those of the substrate and this would greatly contribute to the enhancement of wear resistance.     

表面扩渗Al,Zn处理对ZM5镁合金性能的影响

通过铝锌(Al,Zn)混合粉对ZM5镁合金进行了表面固态扩渗铝锌(Al,Zn)处理,在衬底形成了Mg-Al-Zn合金层.研究结果表明:Mg-Al-Zn合金层主要由Mg-Al-Zn固溶体和Mg-Al-Zn金属间化合物(Al6Mg10Zn,Al5MgllZn4)组成,该合金层不仅使ZM5镁合金表面合金层显微硬度显著提高,而且在盐水浸泡腐蚀过程中,在衬底与腐蚀介质之间起到了良好的屏障作用,从而赋予试样良好的腐蚀性能.     

AZ31镁合金盐浴渗铝改善耐蚀性机制分析

采用真空热扩散渗铝的方法对AZ31镁合金进行表面合金化处理,在不同参数下得到厚度不一的渗铝层,对渗层的显微组织、物相组成进行了分析,并分析了渗铝试样的耐腐蚀性能和显微硬度.绘制了AZ31镁合金基体以及经过400℃扩散渗铝4 h后的试样的极化曲线.结果表明,渗层主要由Mg₁₇Al₁₂,Mg₃Al₂和α-Mg等组成,渗层厚度随扩散温度提高而增加,400℃恒温热扩散4 h时,在基体表面获得了连续且均匀细密的渗铝层,显微硬度值从基体的53 HV提高到80~85 HV,同时,该方法使得镁合金的自腐蚀电位提高了约105 mV,而镁合金的自腐蚀电流密度降低了一个数量级,这表征着镁合金的耐蚀性能得到提高.     

纯镁和镁合金强流脉冲电子束表面合金化性能

利用强流脉冲电子束对纯镁及镁合金AZ31和AZ91HP进行表面合金化处理。用光学显微镜和扫描电镜对表面处理层形貌和组织进行了分析,腐蚀性能和摩擦磨损测试表明:纯镁表面合金化铝后,样品抗5%NaCl溶液腐蚀性能得到显著提高,维钝电流降低2个数量级以上;而镁合金AZ31以及AZ91HP表面合金化Cr、TiN后,耐磨性均得到提高。     

镁合金腐蚀的研究现状及发展趋势

介绍镁合金的腐蚀行为,包括腐蚀机理、腐蚀类型、负差数效应以及腐蚀表面膜,并着重阐述了杂质元素、各类合金化元素RE、Al、Ca、Zn等以及相组成对镁合金耐蚀性的影响,并对耐蚀镁合金的发展提出了展望.     

Influence of substrate composition on the formation of phytic acid conversion coatings

In this paper, the formation and corrosion resistance of the phytic acid conversion coatings on Mg, Al, and AZ91D magnesium alloy were contrastively investigated using scanning electronic microscopy (SEM), Auger electron spectroscopy (AES), Fourier transform infrared spectroscopy (FTIR), electronic probe microscopic analyzer (EPMA), electronic balance, and electrochemical methods. The influence of phytic acid conversion coating as a middle layer on the properties of the paint on magnesium alloys was also investigated. The results show that the formation process of the conversion coatings is evidently influenced by the compositions of the substrate. The coating on pure aluminum is thinner and compacter than that on pure magnesium and the coating formed on α phase in AZ91D magnesium alloy is thinner but denser than that on β phase. The phytic acid conversion coatings formed on Mg, Al, and AZ91D magnesium alloy can all increase their corrosion resistance. The active functional groups of hydroxyl and phosphate radical are rich in the conversion coatings, which can improve the bonding between the organic paint and magnesium alloy and then improve their corrosion resistance.     

The effect of Ca on corrosion behavior of heat‐treated Mg–Al–Zn alloy

The effect of 0.5, 1.0, and 1.5 wt% Ca additions on the microstructure and corrosion resistance of the heat‐treated Mg–Al–Zn alloy was investigated. Addition of 0.5 wt% Ca did not form any new phase but suppressed the discontinuous precipitation of the β ‐Mg₁₇Al₁₂ phase by being dissolved in both the second phase and magnesium matrix. In the materials containing higher amounts of Ca, however, metallographic investigation shows that Ca added to Mg–Al–Zn can obviously decrease the size of β ‐Mg₁₇Al₁₂ and forms Al₄Ca intermetallic compounds in the shape of bone‐like morphology. The corrosion tests used include constant immersion technique, and potentiodynamic polarization experiments and salt spray test. Surface examination and analytical studies were carried out using optical and scanning electron microscopy, EDX, and XRD. The results of corrosion tests show that magnesium alloy Mg–Al–Zn with 1.0 wt% Ca addition has the best corrosion resistance behavior.     

镁合金表面冷喷涂铝涂层的热处理研究

使用冷喷涂方法在铸态AZ91D镁合金基体上沉积了纯Al涂层,所得涂层组织致密,厚度均匀,与基体结合良好,孔隙率小于1%.随后用机械减薄的方法使Al涂层的厚度减薄到135 μm,对减薄后的试样在真空加热炉中分别进行了400℃×20 h和400℃×40 h的热处理.结果显示随着保温时间的延长,Al涂层全部转化为较高硬度和较...     

AZ91D镁合金表面激光熔覆Al-TiC涂层组织和性能的研究

目的研究Al-TiC涂层组织和性能的特性,以提高镁合金涂层的硬度和耐蚀性能。方法采用Nd:YAG固体激光器,在AZ91D镁合金表面通过激光熔覆制备Al-TiC涂层,采用光学显微镜、X射线衍射仪、显微硬度计、电化学工作站,对熔覆层的组织形貌、物相结构、显微硬度和耐蚀性能进行测定和分析。结果 Al-TiC涂层的主要组成相有AlTi_3(C,N)_(0.6),Al_3Mg_2,Mg_2Al_3,Al和TiC等。激光熔覆层的厚度约为0.35 mm,表面成型良好,结合层晶粒细小,熔覆层与镁合金基体之间结合良好,呈大波浪形。熔覆层试样的平均显微硬度为224HV,约为基体显微硬度(62HV)的4倍,由此表明熔覆层对镁合金硬度有明显的增强作用。镁合金基体的自腐蚀电位为-1.475 V,自腐蚀电流密度为7.556×10~(–5) A/cm~2,熔覆层试样的自腐蚀电位为-1.138V,自腐蚀电流密度为4.828×10~(–5) A/cm~2,与镁合金基体相比,熔覆层的腐蚀电位值增加,腐蚀电流密度值变小,熔覆层的耐蚀性能得到提高。结论采用激光熔覆技术,能够在AZ91D镁合金基体表面制备Al-TiC涂层,由于硬质相AlTi_3(C,N)_(0.6),Al_3Mg_2,Mg_2Al_3,TiC等的存在,熔覆层的显微硬度和耐蚀性能显著提高。     

激光表面强化对镁合金在模拟体液中腐蚀行为的影响

目的通过对镁合金表面进行激光强化处理,改善医用AZ91D镁合金在模拟体液中的耐腐蚀性能。方法采用不同脉宽的Nd:YAG脉冲激光对医用AZ91D镁合金表面进行处理,激光能量密度分别为28、23、18 J/mm~2,对激光处理后镁合金强化层的组成、显微结构、厚度、元素分布以及耐腐蚀性能等进行测试和分析。结果 AZ91D经过激光强化处理后形成致密的强化层,强化层中相的组成与基材相的组成相同,均由α-Mg和β-Mg_(17)Al_(12)组成,强化层的厚度达到300μm。Mg和Mg_(17)Al_(12)的X射线衍射峰均向低角度偏移(约0.2°),且镁合金表面晶粒均得到细化,β相的大小从平均55.705μm减小到平均6.447μm。EDS分析表明,经过激光处理后,Mg的质量分数由82.88%减少为70.13%,Al的质量分数由16.28%增加为28.08%,且Al的分布更均匀。激光处理后,镁合金在模拟体液中的电化学测试结果表明,镁合金的腐蚀电位从原来的-1274mV增加到-1215 mV,腐蚀电流密度从8.920×10~(-5) A/cm~2减小为8.826×10~(-6) A/cm~2,同时,阻抗也从原来的1000Ω增加到60 000Ω,可知激光强化镁合金的耐腐蚀性能较原始镁合金的耐腐蚀性能均有一定程度的改善。结论医用AZ91D镁合金在不同脉宽的Nd:YAG脉冲激光处理后,表面晶粒得到了细化,强化层中富集Al,在模拟体液中的耐腐蚀性能得到改善。     

Studies on thermal oxidation of Mg-alloy (AZ91) for improving corrosion and wear resistance

The present investigation concerns development of an adherent stable oxide layer on the surface of a Mg alloy, AZ91 (8.3-9.7% Al, 0.13% Mn, 1.0% Zn, 0.50% Si, 0.10% Cu, 0.03% Ni, 0.30% other, balance Mg) by thermal oxidation to improve wear and corrosion resistance in simulated body fluid. Oxide layer was developed by thermal oxidation of freshly polished AZ91 samples in air at 200 °C, 300 °C and 400 °C for 8, 16 and 25 h. Following thermal oxidation, a detailed characterization of the oxide layer was undertaken in terms of microstructure and phases. The wear, corrosion resistance and biocompatibility were evaluated in details. The oxide layer mainly consists of oxides of magnesium (MgO₂ and MgO) phases. The corrosion resistance (in simulated body fluid) and wear resistance of the oxidized surface were improved. Thermally oxidized Mg-Al alloy (AZ91) treated at 200 °C for 25 h have shown best biocompatibility in terms of cell (L-929 mouse fibroblast cell line) proliferation.     

STUDY ON THE TANTALIZING ON THE SURFACE OF TITANIUM ALLOY BY NET-SHAPE CATHODE GLOW DISCHARGING

A new net-shape cathode sputtering target which has a simple structure and a high sputtering was put forward. The multiple-structure made of alloying and coating layers of tantalum was achieved on the surface of TC4 (Ti6AI4V) using this method in double glow surface alloying process. The tantalized samples were investigated by SEM, XRD and electrochemical corrosion method .Results show the complicated tissue of pure tantalizing layer and diffusion layer was successfully formed on the surface of TC4 with the method of net-shape cathode glow discharge, which further improved the corrosion-resistance of TC4 and formed good corrosion-resistant alloys.     

汽车发动机用AZ91D合金的表面喷涂与性能

采用热喷涂工艺在压铸态AZ91D合金表面制备了Al涂层,研究了热处理温度和保温时间对AZ91/Al涂层界面组织形貌的影响,并对比分析了扩散层的耐腐蚀性能和耐磨性能。结果表明,热处理前Al涂层与基材为机械结合,热处理后Al涂层与AZ91合金基材的界面处可形成冶金结合扩散层,且随着保温时间延长,扩散层厚度不断增加;热处理温度在375 ℃以下时扩散层主要由β-Mg₁₇Al₁₂相构成,375 ℃×8 h热处理后为α-Mg+β-Mg₁₇Al₁₂相,425 ℃×1 h热处理后为γ-Mg₂Al₃和β-Mg₁₇Al₁₂相。AZ91合金基材和扩散层腐蚀电位从高至低顺序为γ>β>α+β>AZ91合金基材,扩散层的腐蚀电流密度均低于AZ91合金基材,阻抗谱图中容抗弧半径从大至小顺序为γ>β>α+β>AZ91合金基材,扩散层的耐腐蚀性能均优于AZ91合金基材;γ、β和α+β扩散层的摩擦稳定性系数都高于AZ91合金基材,而磨损速率和磨痕宽度都要小于AZ91合金基材,其中β扩散层的磨损速率和磨痕宽度最小,具有最佳的抵抗磨损的能力。     

铝合金在海洋环境中的腐蚀研究(Ⅱ)--海水全浸区16年暴露试验总结

总结了铝合金在青岛海域海水全浸区暴露16年的腐蚀结果，防锈铝LF2Y2，LF6M（BL），F21M，180YS在海水全浸区有好的耐蚀性，工业纯铝L4M，锻铝LD2CS的耐蚀性较差，无包铝层的硬铝LY12CZ和超硬铝LC4CS在海水中的耐蚀性很差，硬铝，超硬铝的包铝层起牺牲阳极作用，使基体受到保护，海生物污损对铝合金在海水中的腐蚀有明显影响，镁、锰能提高铝的耐海水腐蚀性，硅明显降低铝的耐蚀性，铜严重损害铝的耐蚀性，腐蚀电位较负的铝合金耐海水腐蚀性较好，腐蚀电位较正的铝合金耐海水腐蚀性较差。     

Al/Cr复合涂层对Ti2AlNb合金抗热腐蚀性能的影响

目的改善Ti2AlNb合金在高温腐蚀盐环境中的耐热腐蚀性能。方法在Ti2AlNb合金表面通过双层辉光等离子渗铬及磁控溅射镀铝技术制备Al/Cr复合涂层,分析涂层热腐蚀前后的微观形貌和物相组成,并探究涂覆Na2SO4盐膜的试样在不同温度下(750、850、950℃)的热腐蚀行为。结果Al/Cr复合涂层组织均匀致密,且与基体结合良好,厚度约73μm,由表及里依次由Al沉积层、Al/Cr合金层、Cr沉积层、Cr扩散层四部分组成。经不同温度Na2SO4盐热腐蚀后,Al/Cr复合涂层腐蚀程度均显著小于合金基体。涂层试样经750~850℃Na2SO4盐热腐蚀后质量变化较小,850℃腐蚀增重仅0.525 mg/cm^2,而经历950℃、40 h熔盐热腐蚀后失重达到73.571 mg/cm^2,且试样截面出现剥离、脱落现象,Al/Cr复合涂层抵抗热腐蚀能力减弱。结论具有涂层保护的试样抗热腐蚀性能明显优于合金基体。Al/Cr复合涂层在750~850℃Na2SO4盐环境中具有良好的热腐蚀抗力,而更高温度段(850~950℃)的热腐蚀抗力下降。Al/Cr复合涂层在Na2SO4盐环境中良好的抗热腐蚀性得益于涂层中Al、Cr元素氧化形成以Al2O3、Cr2O3为主的混合氧化膜,有效阻碍外界氧气及腐蚀性介质侵入基体。     

铝合金在海洋环境中的腐蚀研究（Ⅰ）：——海水潮汐区16年暴露试验总结

总结了铝合金在青岛海域海水潮汐区暴露16年的腐蚀试验结果，防锈铝LF2Y2、LF6M（BL）、F21M、180YS在海水潮汐区有好的耐蚀性，工业纯铝L4M、锻铝LD2CS的耐蚀性较差，硬铝LY11CZ（BL）、LY12CZ（BL）和超硬铝LC4CS（BL）的包铝层起着牺牲阳极作用，使基体受到保护，海生物污损对铝合金的腐蚀有明显影响，镁，锰能提高铝在海水潮汐区的耐蚀性，硅明显降低铝的耐蚀性，铜严重损害铝的耐蚀性。