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1.
利用微弧氧化法在7475铝合金表面制备一层氧化膜,通过SEM、EDS、XRD等手段对其表面-界面形貌、化学元素组成和物相进行了分析,采用能谱仪对表面和结合界面进行了面扫描和线扫描分析,并用划痕法表征了氧化膜界面结合强度。结果表明,微弧氧化后7475铝合金表面形成一层粗糙多孔的氧化膜,其组成元素与氧化膜表面的物相相应分布;O原子以扩散形式与Al原子原位生长形成Al_2O_3,主要由α-Al_2O_3、γ-Al_2O_3组成,Si原子在表面氧化形成富集的Si-Al-O相;氧化膜厚度约为50μm,由间隙层、致密层和膜-基过渡层组成,与基体的界面结合强度为71.05 N。  相似文献   

2.
目的提高铝合金钻杆材料微弧氧化膜层的性能。方法在电解液中加入0~4 g/L的SiC微粉,对7E04铝合金钻杆材料表面生成的微弧氧化膜层进行改性,研究了微弧氧化膜层的氧化电压-时间曲线、厚度、显微硬度、表面形貌、膜层元素含量、相组成和耐蚀性。结果随着SiC微粉质量浓度的增加(0、1、2、3、4 g/L),氧化电压不断增加,在4 g/L时几乎达到550 V。微弧氧化膜层的厚度和显微硬度增加,各浓度下的膜层厚度分别为42.3、43.6、45.0、45.3、50.0μm,膜层显微硬度分别为341.8、375.2、394.4、405.1、436.8MPa。同时,放电孔的孔径和烧结盘的尺寸也逐渐增加。在微弧氧化过程中,SiC被氧化成SiO_2,基体中的Al被氧化成α-Al_2O_3和γ-Al_2O_3,膜层中的相组成主要有α-Al_2O_3、γ-Al_2O_3、SiO_2和莫来石。同时,随着SiC微粉浓度的增加,膜层中的C、Si元素含量增加,Al元素和O元素的含量降低。膜层的腐蚀速率分别为1.11×10~(-1)、3.598×10~(-2)、5.223×10~(-2)、6.762×10~(-2)、1.323×10~(-1) mm/a,呈现出先减小后增加的趋势,耐蚀性先增加后降低。结论 SiC微粉的添加增加了膜层的厚度,改变了膜层的表面形貌,同时提高了微弧氧化膜层的显微硬度、耐蚀性等性能。  相似文献   

3.
在相同参数下对Si C_p/6092铝基复合材料进行了不同时间的微弧氧化处理,记录了电解液温度的变化,测定了微弧氧化膜的膜层厚度。利用SEM和XRD分析了氧化膜的微观形貌和相组成。结果表明,氧化初期氧化膜生长较快,20 min后生长速度趋于平稳;氧化膜表面分布着微小孔洞和细小裂纹,随着时间的增加,孔洞尺寸变大、数量变少,表面粗糙度增加;氧化膜主要由α-Al_2O_3相、γ-Al_2O_3相和莫来石相组成。  相似文献   

4.
本文采用恒温氧化实验方法,在900~1150℃下测试了NiAl-28Cr-6Mo共晶合金的氧化性能,分析了合金的氧化动力学,SEM观测了合金表面以及横截面的形貌。研究表明,NiAl-28Cr-6Mo共晶合金在900~1100℃下合金表面生成了连续的Al_2O_3氧化膜,具有较好的抗氧化性能;900~1000℃氧化膜主要由θ-Al_2O_3和Cr_2O_3组成,随着恒温氧化温度的升高,θ-Al_2O_3和Cr_2O_3减少,α-Al_2O_3增多,1100℃下的氧化膜表面则主要由细小、致密的α-Al_2O_3组成;氧化过程中,表面氧化膜存在着θ-Al_2O_3→α-Al_2O_3的相变过程;θ-Al_2O_3较α-Al_2O_3的保护性差导致1000℃合金氧化增重大于1050℃和1100℃;1150℃下共晶合金氧化膜发生剥落,没有形成完整的Al_2O_3氧化膜导致合金的抗氧化性能恶化,氧化增重迅速增加。  相似文献   

5.
在铝酸钠电解液体系下,对7A04超硬铝合金进行不同时间的微弧氧化处理,通过SEM和XRD对氧化陶瓷层的微观结构和相组成进行分析,研究氧化时间对陶瓷层的厚度、显微硬度和陶瓷层与基体结合力的影响。结果表明:膜层微观表面凹凸不平,呈火山喷口状形貌,该膜主要由γ-Al_2O_3和极少量α-Al_2O_3组成。随着氧化时间的增加,陶瓷膜层的厚度不断增加,陶瓷膜层的显微硬度先上升后下降,氧化时间为50 min的膜层达到最大硬度1210 HV0.1。陶瓷层与基体间呈冶金结合且膜层致密。  相似文献   

6.
在含有纳米TiO_2的电解液中对铝合金进行微弧氧化处理,用以研究掺杂纳米TiO_2对铝合金微弧氧化成膜机理及性能的影响。利用扫描电镜(SEM)观察微弧氧化膜形貌,能谱仪(EDS)分析膜层Ti、Al、O等元素含量,X射线衍射仪(XRD)分析相组成,测定膜厚、硬度和氧化液中TiO_2表面电荷,建立了掺杂改性模型。结果表明,加入纳米TiO_2后,氧化初期电压随TiO_2添加量增加逐渐升高、5min后电压逐渐降低;氧化膜表面孔洞数量和尺寸减小,成膜效率、膜层致密度和表面疏松层硬度提高。纳米TiO_2在氧化膜表面均匀分布,截面不均匀分布。氧化膜主要由γ-Al_2O_3、Mullite和少量Si组成。  相似文献   

7.
含Li_2CO_3的电解液中形成ZAlSi12Cu2Mg1合金微弧氧化膜的表征   总被引:1,自引:0,他引:1  
在Na2SiO3+NaOH体系电解液中加入Li2CO3调整电解液组成,对ZAlSi12Cu2Mg1合金进行微弧氧化。利用涡流测厚仪、XRD、SEM、EDS对氧化膜进行表征。结果表明:Li2CO3含量从4.0g/L增加到6.0g/L,膜层厚度从71μm增加到126μm;微弧氧化过程中,随氧化时间的延长电流呈下降趋势,且随着Li2CO3含量的增多,电流下降速率增大;SEM分析可知,随Li2CO3加入量的增加试样表面氧化膜的粗糙程度先降低后增加,膜层表面微孔数量减少,孔径增大,呈现出的熔融状态更为明显;XRD分析表明,氧化膜主要由Mullite和Al2O3相组成。由EDS分析可知,氧化膜表面主要分布有O、Al和Si及少量的Na和Mg元素。  相似文献   

8.
研究DZ406合金及渗铝涂层在1100℃的氧化行为,利用扫描电镜(SEM)观察其表面形貌和截面组织.结果表明,合金在氧化初期表面产物含有大量的晶须状θ-Al_2O_3,后期表面产物主要为α-Al_2O_3和由Ni、Co、Cr等元素组成的尖晶石相;渗铝涂层表面产物在氧化初期晶须状θ-Al_2O_3较少,一定时间后全部转变为α-Al_2O_3.  相似文献   

9.
采用微弧氧化技术在不同Mn含量的铝合金门窗表面进行了改性处理,研究了基体合金元素Mn对表面陶瓷层膜厚、显微硬度、形貌和物相的影响,并分析了其作用机理。结果表明,随着微弧氧化时间的增加,含0.5%Mn和含1.5%Mn的铝合金试样的表面陶瓷层厚度和显微硬度都表现为逐渐增加的趋势,且在相同的微弧氧化时间内,含1.5%Mn的铝合金试样的表面陶瓷层厚度更大、显微硬度更低。Mn含量为0.5%的铝合金表面陶瓷层中有γ-Al_2O_3相和少量α-Al_2O_3相,而Mn含量为1.5%的铝合金表面陶瓷层中只有γ-Al_2O_3相。  相似文献   

10.
在含石墨微粒的硅酸钠电解液中,采用不同的电流密度(1, 5, 10,15和20 A/dm~2)在ZL108铝合金上制备了微弧氧化(MAO)膜层。利用SEM、EDS、XRD、涡流测厚仪和显微硬度计对微弧氧化膜层的特性进行了研究。结果表明,随着电流密度的增加,微弧氧化膜层的增厚导致氧化电压增加。微弧氧化膜表面多孔,微孔的直径和烧结盘尺寸逐渐增加。膜层表面C、Si元素的相对含量随电流密度增加而增多,C元素在膜层表面呈均匀分布,膜层截面C元素主要集中在膜层外侧。膜层主要由SiC, SiO_2,θ-Al_2O_3,α-Al_2O_3组成, SiC相来源于石墨与SiO_2反应。随电流密度增大,膜层硬度增加。膜层耐蚀性呈先升高后降低的趋势,并在5 A/dm~2时膜层腐蚀速率最低。  相似文献   

11.
The influence of an initial preinternal oxidation treatment in Co/CoO on the subsequent oxidation behavior of a series of dilute Co-Cr alloys (containing 0–1.5 wt. % Cr) in 105 and 103 Pa oxygen at 1473–1623 Khas been investigated. Particular emphasis has been placed on determining the solubility and mobility of Cr3+ ions in CoO. Use has been made of subsequent annealing in argon .  相似文献   

12.
A study on the high-temperature growth of thick wustite films on low-carbon steel under a time-dependent oxygen partial pressure law is reported. The experimental data were interpreted using a general formulation of oxidation under non-time-constant gas activity. Good agreement between the theory and the experimental data was obtained. The physical reasons that justify the change of the oxygen activity at the steel-atmosphere interface as observed during the oxidation process are discussed also.  相似文献   

13.
为了测定不同氧化时间以及铬含量对高温条件下钢材表面氧化铁皮组织和厚度的影响,将Fe-5Cr钢与Fe-10Cr钢在1000 ℃空气条件下氧化60~180 min,采用增重法绘制其氧化动力学曲线,并利用光学显微镜、能谱仪和X射线衍射仪对氧化铁皮的断面形貌和物相进行研究。结果表明,两试验钢氧化初期为“气-固”反应,中后期为“气相-氧化铁皮-固相”反应。两试验钢氧化铁皮结构均由外氧化层、内氧化层和内氧化区域组成。当氧化时间为180 min时,Fe-10Cr钢检测到了内氧化物Cr2O3。空气中氧元素向内扩散与基体中铬元素发生反应生成内氧化物Cr2O3,再与氧化铁皮层中的FeO发生固相反应生成尖晶石结构产物FeCr2O4。随着氧化时间的增加,由于内氧化物Cr2O3不断受到内氧化层的包裹而转为外氧化,内外氧化的转变使得基体不断被腐蚀,氧化铁皮厚度不断增加。  相似文献   

14.
The preferential oxidation of carbon in an Fe-0.8%C alloy during the first 60 min of oxidation in air at 400°C was studied by a thermogravimetric method and by measuring the quantity of evolved carbon oxides. The morphology of the external oxide surface depended on the type of exposed phase—a rosettelike oxide grows over ferrite, whereas the oxide surface over cementite is relatively smooth. A possible mechanism for the preferential oxidation of carbon and its subsequent cessation is proposed.Formerly of Institute of Materials Engineering, Academy of Mining and Metallurgy, Cracow, Poland.  相似文献   

15.
A theoretical study on the high-temperature oxidation of thick oxide films grown under a time-dependent gas partial pressure is reported. The diffusion across the film is assumed to be the rate-limiting step of the overall reaction, and Wagner's hypotheses were used as the starting point for our reasoning. A general formulation for the oxidation under no time constant gas pressure, in terms of a time-dependent answer function is given. The effect of an external electric field on the reaction rate is also reported when a constant current density,J, is applied to the oxide scale. If the oxide is a good electronic conductor atJ=0 andt , we found that the reaction rate assumes formally the well-known Wagner's expression of the rate constant but with a gas partial pressure at oxide/gas interface which is a time function. If the oxide is a good ionic or electronic conductor, the effect due to an external electric field,J 0, on the reaction rate is the same as predicted by the Wagner's theory.  相似文献   

16.
铁基合金粉末氧化行为   总被引:2,自引:1,他引:1  
采用质量变化、氧含量测定、XRD、SEM和能谱分析研究铁基合金粉末500℃氧化行为及氧化机理。结果表明,氧化质量增量、氧含量随时间变化明显,前期呈线性关系,后期则呈抛物线关系;前期由于氧化时间较短,铁基合金粉末颗粒与氧反应不明显,后期氧与颗粒表面反应,生成Fe、Cr和Ti的氧化物,并形成致密的氧化膜;铁基粉末形成(Fe,Cr)2O3相,随着氧化时间的延长,形成的(Fe,Cr)2O3相衍射峰强度增强。  相似文献   

17.
Incoloy-825-sheet specimens were exposed to four different atmospheres; steam, synthetic air, CO2, and CO2 diluted with argon. The duration of exposure was varied from 2 min to 100 hr in the temperature range of 600–1300°C. A comparison of the results in these four atmospheres showed the maximum weight gain in specimens exposed under steam, while the minumum value was obtained in specimens subjected to diluted CO2. The alloy obeyed similar reaction kinetics while exposed to all the atmospheres under consideration. The overall domination of parabolic rates was observed at 800–1000°C. For still higher temperatures, a transition from the parabolic to the cubic rate law was observed. Thermal cycling did not show any appreciable effects on the reaction kinetics of the alloy when specimens were cycled between test temperatures and 500°C, and finally cooled to ambient temperature.  相似文献   

18.
铁在双相Fe—Cu合金中的内—外氧化   总被引:1,自引:0,他引:1  
三处Fe-Cu合金在氧分压低于氧化铜平衡分解压条件下的高温氧化结果表明,合金中同时发生了活泼组元铁的内氧化和外氧化,外氧化膜为单一铁的氧化物,内氧化区中氧化铁和金属铜继承了原始合金中两相的分布。内氧化区前沿的合金中未发现铁的贫化。这种氧化膜结构的单相合金中罕见而在双相合金中较为普遍,被认为是双相合金中两组元间有限地互溶度使得氧在合金中的过饱和程度比在固溶体合金中更强烈的结果。  相似文献   

19.
An oxidation test with rapid temperature cycling was developed to evaluate small coated parts. The samples in the form of wire or foils are resistively heated with a high-current AC power supply, allowing fast heating and cooling of the samples. Fast temperature cycling of the samples permits to complete more than 100 cycles in one day. A variety of steels coated with silicon diffusion coatings were tested and the results compared with oxidation via traditional thermal cycling. The test accurately predicts enhanced performance for siliconized 1010 steel, an increase by a factor of three for the life of siliconized 302 stainless steel, and an inadequate siliconized coating for 410 stainless steel. Details of the rapid temperature cycling apparatus as well as testing of the coated steels are described in the paper.  相似文献   

20.
Titanium aluminide (Ti3Al–Nb) has potential for high-temperature applications because of its low density and high-temperature strength. This research is aimed at improving the high-temperature oxidation resistance of a Ti3Al–Nb alloy by modification of its composition. The oxidation rates of Ti3Al–Nb alloys were measured from 600 to 900°C in air. The oxide layer was examined by X-ray diffraction, scanning electron microscopy, and electron probe microanalysis. The experimental results reveal that alloys with added Nb tend to form denser oxide layers and that oxidation rate can be reduced by increasing Nb content (up to 11 at.% in this study), which is in good agreement with other investigators. The only exception is a Ti65Al25Nb10 alloy, which shows better oxidation resistance than the commercial Ti65Al24Nb11 alloy. The oxidation resistance of Ti65Al25Nb10 alloy can also be improved slightly by the addition of small amounts of Si or Cr. An increase in the oxidation resistance of Ti65Al25Nb10 alloy containing Y was observed at 900°C but not at 800°C or below. The parabolic oxidation rate equation is adequate to describe the high-temperature oxidation reaction of the Ti3Al–Nb alloys in the atmosphere.  相似文献   

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