Al对Cu-20Ni-19Fe合金微观组织和高温抗氧化性能的影响

为了解决Cu-Ni-Fe惰性阳极在铝电解过程中高温抗氧化性能差的问题,采用真空熔炼法制备不同Al含量的Cu-20Ni-19Fe-xAl(x=0%,6%,8%,10%,质量分数,下同)合金,于850℃和1.013×10~5 Pa氧分压下进行高温氧化实验,氧化时间为100 h,研究Al添加量对合金微观组织结构及高温氧化性能的影响。结果表明:铸造Cu-20Ni-19Fe合金由富Ni/Fe的枝晶相(γ_1)和富Cu, Ni的基体相(γ_2)组成;添加6%Al的Cu-20Ni-19Fe合金,Al固溶在合金基体中;添加8%和10%Al的Cu-20Ni-19Fe合金,微观组织中形成了针状或块状NiAl相,且NiAl相随Al含量的增加而增多;Cu-20Ni-19Fe合金在850℃和1.013×10~5 Pa氧分压下氧化动力学呈直线规律;添加Al元素后,合金的高温氧化动力学曲线由直线转变为指数规律,Al含量越高,合金氧化速率指数越小。Al元素的加入提高了Cu-20Ni-19Fe合金的高温抗氧化性能,使其有望成为惰性阳极铝电解中的备选阳极材料。     

Fe3Al合金铸造工艺性能的研究

介绍了Fe3Al合金铸造工艺参数的测试过程,分析了结果及产生这一结果的原因,在此基础上确定了Fe3Al合金的铸造工艺设计原则,从而为指导生产提供了依据。解决了Fe3Al系列合金优良的高温性能与低劣的铸造工艺性能这对矛盾,使这类合金得以实现推广应用。     

Al 对 Fe3Si 基有序合金 800 e 氧化行为的影响

通过800 ℃高温下的氧化实验,结合X射线衍射仪、扫描电子显微镜、电子探针显微分析仪,研究了金属Al复合Fe3Si有序合金的高温氧化行为．结果表明:元素Al很好地改善了Fe3Si的高温抗氧化性能,其氧化动力学曲线由抛物线加直线的混合规律转变为完全的二次抛物线型,且氧化增重降低了近一个数量级;氧化动力学主要机制是Al通过亚晶界由基体内部向外扩散并形成保护性氧化膜Al2O3 ,阻止Si和Fe的向外扩散氧化;同时氧化膜保护性的好坏还受到氧化产物Al2O3的相结构以及扩散通道等诸多因素的影响．     

原位合成VC和TiC颗粒对Fe3Al基合金显微组织的影响

以Fe3Al金属间化合物作为基体,采用反应铸造法制备了含VC,TiC颗粒Fe3Al基合金并研究了颗粒相在Fe3Al合金中的形成机理及颗粒相的加入对Fe3Al基合金显微组织结构的影响。结果表明,TiCp在高温液态熔体中原位合成,且在基体中均匀分布,可以作为异质形核核心而细化Fe3Al基合金铸定组织,从而改善Fe3Al合金的热加工性能;VCp是在固相中形核并长大的,对铸态组织的细化作用下明显,但其对热加工后再结晶组织的细化作用甚于TiCp。     

Al元素对Ti-Si共晶合金恒温氧化行为的影响

采用真空非自耗电弧炉制备了不同Al质量分数的Ti—Si共晶合金,研究了合金在800℃下的恒温氧化行为.结果表明:添加合金元素Al使得合金的800℃氧化动力学曲线偏离了Ti—Si共晶合金的立方规律,接近于抛物线规律;适量的元素Al可显著提高Ti—Si共晶合金的抗氧化性能.     

T91钢热浸镀铝及其在水蒸汽中的循环氧化行为

研究SA213T91钢热浸镀铝后并退火后样品在90%Ar+10%H2O气氛中于600,650和700℃下的循环氧化行为.研究结果表明:T91钢热浸镀铝并退火后样品在表面形成Fe2Al5金属间化合物层,该层中有贯穿Fe2Al5层的裂纹;Fe2Al5层下为扩散层;镀层表现良好的抗氧化性能;在600℃氧化速率缓慢,样品表面仅生成极薄的Al2O3膜,其生长方式主要由Al向外扩散为主,而在650℃和700℃时氧化质量增量增大;在循环氧化过程中,由于基体和镀层的热膨胀系数不匹配,镀层在降温和升温过程中将受到循环应力作用,镀层中裂纹增加,并导致镀层剥落.     

Si、V对Fe-Al-Cr合金抗高温氧化性的影响

本文通过900℃10h高温氧化实验测试添加不同合金元素(Si、V)的Fe-Al-Cr系高铝钢的抗高温氧化性。经测试,Fe-Al-Cr-Si的抗高温氧化性优于Fe-Al-Cr与Fe-Al-Cr-V合金。实验发现Fe-Al-Cr合金在高温环境下经历氧化物生成-脱落-基体氧化的动态过程,其抗高温氧化性主要取决于Fe/Al2O3界面的结合强度,而不是与铝含量呈正相关。通过密度泛函理论计算合金元素对金属/氧化物界面结合能的影响,解释了Si、V对Fe-Al-Cr系合金耐高温氧化性影响的机理:Fe/Al2O3界面结合力来自Fe-O的共价作用,Si使界面结合能从-7.16eV降低至-7.41eV,使Al2O3与基体结合更加紧密,改善了合金的高温抗氧化性;V提高界面结合能至-6.06eV,使界面容易失效,导致Al2O3的脱落,破坏了合金抗高温氧化性。     

AlCoCrFeNi高熵合金的高温氧化性能

测定AlCoCrFeNi高熵合金高温氧化后的氧化动力学曲线，采用X射线衍射仪、扫描电镜和能谱仪等分析合金氧化层的物相、形貌、结构和成分，利用硬度计测定不同温度下氧化产物的硬度，从热力学和动力学角度深入分析AlCoCrFeNi高熵合金的氧化机理.结果表明：AlCoCrFeNi高熵合金在800～1 000℃下具有较好的抗氧化性能，高于1 000℃时合金退化较为明显；AlCoCrFeNi高熵合金800℃氧化时Al与O元素亲和力最大，并且高熵合金中Al原子扩散速率最大，Al率先在合金表面形成连续的Al₂O₃膜，随着温度的升高，其他原子也扩散至表面发生氧化反应，合金表面出现Cr₂O₃和尖晶石等，氧化物逐渐长大，1 100℃时长大的尖晶石易从合金表面脱落；随着氧化温度的升高，AlCoCrFeNi高熵合金的显微硬度逐渐升高.     

不同铸造方法对船用螺旋桨毂成型质量的影响

采用ZCuAl9Fe4Ni4Mn2铝青铜合金为结构材料,研究3种不同铸造方法对船用桨毂组织性能的影响。结果表明,重力铸造桨毂窗口下方有大量氧化夹渣存在;低压铸造容易获得组织致密、性能优良的桨毂,但工序较多;离心铸造可获得较为致密的桨毂断面组织,二次氧化夹渣状况较重力铸造得到明显改善,但离心转速超过150r/min时,容易产生缩孔和缩松。     

镍钴基高温合金的氧化动力学与界面结合性能

采用XRD,SEM和静态增重法等研究镍钴基GH783高温合金的氧化行为和氧化过程动力学,并通过纳米划痕试验对膜基结合性能进行表征。研究结果表明:合金在500～700℃没有生成氧化膜,在800℃时开始生成由Fe2O3和少量Fe3O4组成的氧化层,900℃时生成的氧化膜中Fe3O4含量增多;合金在800℃氧化100 h后,合金表面生成致密的Fe2O3-Fe3O4复合物氧化膜,膜厚约为15μm;合金的氧化动力学曲线符合抛物线规律,抛物线速度常数为3.44×10-5mg2/(cm4·h);随着氧化时间增长,氧化膜与基体的界面结合性能愈趋良好,于800℃氧化100 h后膜基结合力达8.92 N。     

Corrosion-wear behavior of nanocrystalline Fe_(88)Si_(12) alloy in acid and alkaline solutions

The corrosion-wear behavior of a nanocrystalline Fe_(88)Si_(12) alloy disc coupled with a Si_3N_4 ball was investigated in acid(pH 3) and alkaline(pH 9) aqueous solutions. The dry wear was also measured for reference. The average friction coefficient of Fe_(88)Si_(12) alloy in the pH 9 solution was approximately 0.2, which was lower than those observed for Fe_(88)Si_(12) alloy in the pH 3 solution and in the case of dry wear. The fluctuation of the friction coefficient of samples subjected to the pH 9 solution also showed similar characteristics. The wear rate in the pH 9 solution slightly increased with increasing applied load. The wear rate was approximately one order of magnitude less than that in the pH 3 solution and was far lower than that in the case of dry wear, especially at high applied load. The wear traces of Fe_(88)Si_(12) alloy under different wear conditions were examined and analyzed by scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. The results indicated that the tribo-chemical reactions that involve oxidation of the worn surface and hydrolysis of the Si_3N_4 ball in the acid solution were restricted in the pH 9 aqueous solution. Thus, water lubrication can effectively improve the wear resistance of nanocrystalline Fe_(88)Si_(12) alloy in the pH 9 aqueous solution.     

Cyclic oxidation behavior of b-NiAlDy alloys containing varying aluminum content at 1200 1C

b-NiAlDy cast alloys containing varying aluminum content were prepared by arcmelting. The microstructures and cyclic oxidation behavior of the alloys at 1200 1C were investigated. Grain refinement was achieved by increasing aluminum content in the alloy, which is beneficial to selective oxidation. The Ni–55Al–0.1Dy alloy showed excellent cyclic oxidation resistance due to the formation of a continuous, dense and slow-growing oxide scale. In contrast to this, severe internal oxidation as well as large void formation at the scale/alloy interface occurred in the Ni–45Al–0.1Dy alloy. The aluminum content dependence of the reactive element effects in b- NiAlDy was established that Dy doping strengthened the scale/alloy interface by pegging mechanism in high-aluminum alloys but accelerated internal oxidation in low-aluminum alloys during high-temperature exposure.     

在钛合金表面制备Al-Si涂层的方法及其高温抗氧化性

采用低氧压高温快速熔结技术在Ti-6Al-4V合金表面成功地制备出具有抗高温氧化能力的Al-Si熔结涂层. 与其他工艺相比,这种工艺相对简单,且不需要经过长时间的加热处理就能在合金的表面形成一层足够厚度的Al-Si熔结涂层,不仅省时节能,且涂层中的抗氧化元素铝、硅的浓度可通过调整涂层粉末的混合比例来进行控制. XRD检测表明涂层主要由Al、Si、Ti5Si3和TiAl3相组成. 在1 073 K空气中循环氧化105 h的实验结果表明:未经过处理的钛合金试样的氧化增重一直保持着较高的增长速率;而对带有低氧压熔结Al-Si涂层的试样来说,其氧化增重近似呈抛物线规律,显著地提高了钛合金的抗氧化能力.     

A comparative study of four modified Al coatings on Ni3Al-based single crystal superalloy

Four modified Al diffusion coatings (Al, Cr? Al, Al?Si and Cr? Al ? Si coatings) were prepared on Ni3Al based single crystal superalloy IC20. The oxidation tests were carried out at 1 150 °C for up to 100 h. Cyclic hot corrosion tests were carried out at 950 °C for 50 h. The results indicate that the oxidation and corrosion resistance s of IC20 alloy are improved significantly by the coatings, and both oxidation and hot corrosion resistances of the four coatings are rated in the order (from worst to best) of Cr ? Al, Al, Cr ? Al ? Si, Al? Si coatings. It is found that the degradations of Al and Cr ? Al coatings are very quick due to the serious inter-diffusion between the coatings and substrates. The inter-diffusion between Si-containing coatings and substrates is reduced since Si effe ctively retards the outward diffusion of Mo. The weak effects of Cr and benefit effects of Si to the oxidation and hot corrosion resistance were discussed. The hot corrosion degradation mechanism of superalloy IC20 was analyzed.     

树枝状沉淀相的形貌研究

在铁铝黄铜中,Fe_3Al 沉淀呈立方形、花瓣状和树枝状三种形貌.TEM(透射电镜)观察分析表明,这三种形貌反映了沉淀相在粗化过程中的三个阶段.由于基体β′相和沉淀相的晶体结构十分相似,两者的点阵常数又正好是一倍之差,Fe_3Al 初析出时和基体共格.粗化过程中,沉淀颗粒沿<111>晶向生长,这导致了共格的失配和形貌的转化.     

铝合金直接氧化合成Al／Al2O3研究现状

评述了Al-Mg-Si合金直接氧化合成Al/Al2O3的工艺、组织结构、性能，认为其中问题主要为：熔体表面Al/Al2O3氧化生长的不均匀性及Al/Al2O3复合材料组织中的孔隙给其在结构方面应用带来了限制。归纳了机制研究的显微通道假说、Mg作用模型、Si作用模型及诱发机制，指出了其中有待重视的几方面问题：氧在Al熔体中的扩散和传递过程；熔体表氧化物MgO和MgAl2O4的作用；Al-Mg-Si合金氧化组织中的固－气反应特征；Al-Mg-Si合金中Si的SiO2诱发机制以及它与Mg作用机制之间的关联性。     

Oxidation behavior of the Fe-36Al-0.09C-0.09B-0.04Zr alloy at 1250°C

To explore and study the Fe-Al system alloy presenting exceptional oxidation resistance at high temperature, the Fe-36Al-0.09C-0.09B-0.04Zr alloy was designed and developed. The microstructure and hardness of the backing at 1250°C were analyzed and measured. Thermodynamics and kinetics of the oxidation behavior were also analyzed by X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy techniques. The results show that the microstructure of the Fe-36Al-0.09C-0.09B-0.04Zr alloy is FeAl phase at ambient temperature and is stable at 1250°C. It displays the excellent property of oxidation resistance because the oxide film has only the Al₂O₃ layer, and its oxidation kinetics curve obeys the parabolic law at 1250°C. The oxidation mechanism at 1250°C is presumed that in the early oxidation period, the alloy oxidizes to form a large number of Al₂O₃ and a little Fe₂O₃, then, the enrichment of Al caused by Fe oxidization combines with O to form Al₂O₃.     

A comparative study of four modified Al coatings on Ni3Al-based single crystal superalloy

Four modified Al diffusion coatings (Al, Cr–Al, Al–Si and Cr–Al–Si coatings) were prepared on Ni₃Al based single crystal superalloy IC20. The oxidation tests were carried out at 1 150 °C for up to 100 h. Cyclic hot corrosion tests were carried out at 950 °C for 50 h. The results indicate that the oxidation and corrosion resistances of IC20 alloy are improved significantly by the coatings, and both oxidation and hot corrosion resistances of the four coatings are rated in the order (from worst to best) of Cr–Al, Al, Cr–Al–Si, Al–Si coatings. It is found that the degradations of Al and Cr–Al coatings are very quick due to the serious inter-diffusion between the coatings and substrates. The inter-diffusion between Si-containing coatings and substrates is reduced since Si effectively retards the outward diffusion of Mo. The weak effects of Cr and benefit effects of Si to the oxidation and hot corrosion resistance were discussed. The hot corrosion degradation mechanism of superalloy IC20 was analyzed.     

非晶合金短程序研究与回火条件的选取

用核磁共振和穆斯堡尔效应配合研究了Ｆｅ８４Ｂ１０Ｃ６非晶合金的短程序。探讨了用回火非晶合金来研究短程序时的最佳热处理条件。结果表明，在淬态非晶合金中存在体心四方的Ｆｅ３Ｂ和正交型的Ｆｅ３Ｂ两种短程序。当用晶化方法来研究非晶合金的短程序时，推荐采用较低的回火温度（略高於非晶合金的晶化开始温度）和短的回火时间。