Co对K4169合金凝固组织及元素偏析的影响

为研究Co对K4169合金凝固过程的影响,利用手工电弧炉熔炼制备了Co质量分数为0.5%～0.8%的合金,采用扫描电镜(SEM)、能谱仪(EDS)和电子探针(EPMA)对合金的凝固组织及元素偏析进行了研究.SEM观察结果表明,Co能强烈促进Laves相的形成,缩小合金枝晶间偏析区;随着Co质量分数从0.5%增加到0.8%,Laves相由小块状变为筛网状且数量明显增多.经SEM+EDS能谱和EPMA面扫描分析表明,Co能降低Nb在基体中的质量浓度,同时也能降低Fe和Cr在Laves相中的质量浓度而提高Nb、Mo、Ti在Laves相中的质量浓度,因而促进Laves相的析出.分析认为,过多增加Co质量分数对改善合金凝固组织的作用不大.     

Re质量分数对单晶高温合金组织和性能的影响

为了研究Re在单晶高温合金中的作用,基于Rene N5的合金成分,调整了Re的质量分数,拉制了Re质量分数分别为2.5%、3%和3.5%的三种不同镍基单晶高温合金,研究了Re质量分数的变化对合金组织及持久性能的影响.研究结果表明:完全热处理后,三种合金都获得了规则的立方体形γ′相,随着Re质量分数的增加,γ′相尺寸逐渐减小.在982 ℃/248 MPa的持久条件下,随着Re质量分数的增加,合金的持久寿命呈先增加后降低的趋势; 在持久试验过程中,三种合金中均析出了μ相,且随着Re质量分数的增加,μ相含量逐渐增加.在871 ℃/552 MPa的持久条件下,合金的持久寿命随着Re质量分数的增加而增加,没有μ相析出.     

FGH95镍基合金的相组成及γ′相的粒度分布

为了研究FGH95合金的相组成及γ′相的粒度分布,采用电解萃取方法提取热处理态FGH95合金中的γ′相,测定γ′相的相组成结构式;通过XRD曲线测定γ′、γ相的晶格常数及错配度,对萃取的合金中γ′相粉末进行小角度衍射,测定出γ′相的粒度分布.结果表明,经1140℃固溶和时效处理后,合金的组织结构由γ′相（质量分数约为47.8%）、γ相（质量分数约为51.2%）、（Nb,Ti）C、（Nb,W）B₂、Nb₃B₂和Cr₂₃C₆等碳、硼化物（质量分数约为1%）组成,γ′相的结构组成式为（Ni_0.896Co _0.055Cr _0.017Fe _0.031）₃（Ti _0.224Nb _0.134Al_0.473Mo _0.038W _0.066Cr _0.064）,其中,在36~60nm和60~96nm尺寸范围内的γ′相粒子质量分数分别为306%和291%,且细小γ′相在晶内弥散分布,而粗大γ′相分布于较宽的颗粒边界区域,并进一步测算出合金中γ′、γ两相的晶格常数分别为0.35986nm和0.35912nm,晶格错配度为0.2058%.     

一种高硬度铸造镁合金

设计了一种成分（质量分数/%）为Mg-8Zn-6Al-3Cu-3Ca-1.5Mn-1Si的合金,利用金相显微镜、扫描电镜、X射线衍射和维氏硬度计研究了自然冷却、快速冷却及时效处理对合金显微组织和硬度的影响.Mg-8Zn-6Al-3Cu-3Ca-1.5Mn-1Si合金慢冷组织主要由α-Mg、Mg2Cu6Al5、CaMgSi、Mg2Zn3等相构成,没有出现Mg17Al12相.合金经快冷后,抑制了第二相从基体中的析出;时效10 h后,CaMgSi相以细小的块状相均匀析出.合金具有较高的硬度值,在时效时间10 h时最大HV值达到111.     

Al对Mg-5Gd镁合金铸态显微组织和相组成的影响

高性能镁稀土合金中常常含有较多的贵重金属Y和Zr,研究用便宜的元素代替贵重元素而不影响力学性能具有重要的意义.利用OM,SEM-EDS,TEM-EDX研究了质量分数为0～1%的Al对Mg-5Gd合金显微组织、相组成的影响.结果表明:少量的Al能显著细化α-Mg枝晶,Gd与Mg形成Mg5Gd化合物,在晶界和晶内均匀分布.Al与合金中的Gd形成高熔点、硬质的、短棒状Al3Gd分布于晶界,并随着Al含量的增加,Al3Gd的数量增加.当Al含量超过0.8%后,Al与合金中的Mg形成脆性的Al12Mg17相,严重降低材料的塑性.     

稀土La和Ce对ZL201合金组织影响的实验研究

研究了稀土La和Ce的加入量和不同的热处理工艺对ZL201合金组织的影响.实验结果表明,随着稀土La和Ce质量分数的增加,合金的晶粒尺寸得到了明显的细化,黑色片状析出相T(Al12CuMn2)逐渐减少,在晶界上出现了均匀分布的一些不连续的共晶组织.当稀土加入量为0.5%时合金变质效果达到最佳.随着稀土质量分数的进一步增加,合金会发生过变质,晶粒变得粗大.经0.5%稀土变质的合金经T5′处理后,晶界的连续性分布被打断,晶间显现骨骼状的金属间化合物,晶粒内弥散析出质点状强化相.经T5处理比T5′处理后结果更加明显,晶粒内部析出更多、更明显的黑色细小的弥散硬质点相,合金强化相θ′细化也比较明显.     

改型GH4133A合金长期时效的组织稳定性研究

采用显微组织观察和图像分析等方法,研究了改型GH4133A合金在650,700和750℃下长期时效过程中的组织变化.结果表明：在650℃和700℃下时效过程中,合金的组织变化规律一致,组织具有良好的稳定性.而在750℃时效时,500 h后开始出现η相.随时效时间增长,η相进一步析出、变长和粗化,由晶界向晶内生长;γ′相和M23C6数量增加;MC型碳化物则减少.     

不同含量的活性元素钇对K38高温合金1000℃氧化行为的影响

研究添加不同含量活性元素钇（Y）的K38铸造高温合金在1 000℃的氧化行为.结果表明：不添加活性元素Y合金的氧化质量增加明显高于含Y合金.不添加Y的合金和添加0.05%（质量分数,以下同）Y的合金发生了内氧化,内氧化物为Al2O3和TiN.而含0.1%和0.5%Y的合金没有内氧化发生,Y促进了Al的选择性氧化.当Y含量达0.5%时,合金中析出富Y相,降低了合金的氧化抗力.     

固溶冷却方式对K325合金组织特征的影响规律

采用扫描电子显微镜(SEM)、电子探针(EPMA)和差热分析(DTA)等研究了K325合金的铸态组织、凝固行为,以及固溶处理后不同冷却方式对合金组织的影响。结果表明:K325合金铸态组织呈典型枝晶结构,枝晶间分布有条、块状富Nb和Ti的MC型碳化物,其面积分数约0.65%;合金凝固顺序为:L→L+γ→L+γ+MC→γ+MC。采用水冷冷却方式,碳化物主要分布于晶内,其数量和尺寸最小;采用空气冷却,碳化物仍主要分布于晶内,但碳化物数量和尺寸略有提高;采用随炉冷却,二次碳化物沿晶界连续析出,且数量和尺寸显著增加,同时在晶内形成八面体状的MC型碳化物。K325合金固溶处理后采用水冷冷却较为合理。     

K3625高温合金微观组织的研究

实验合金为通过真空感应炉冶炼的不同Al、Ti和B含量的K3625合金。采用扫描电子显微镜(SEM)观察固溶态IN625合金微观组织,用能谱仪(EDS)和透射电镜(TEM)对合金进行析出相鉴定,并研究Al、Ti和B元素的添加对合金微观组织的影响。结果表明:K3625合金铸态凝固组织为树枝晶结构,一次和二次枝晶都比较明显,没有三次枝晶;合金中析出的第二相都是富含Nb元素的MC。添加0.2%Al和0.2%Ti元素对合金枝晶组织和析出相影响很小;而添加0.04%B元素能够促进二次枝晶臂的生长,增大二次枝晶间距。     

Corrosion resistance of Molybdenum Nitride modified Ti6Al4V alloy in HCl solution

The Mo-N surface modified layer on Ti6Al4V alloy was obtained by the plasma surface alloying technique. The structure and composition of the Mo-N modified Ti6Al4V alloy were investigated by X-ray diffraction （XRD） and glow discharge optical emission spectroscopy （GDOES）. The Mo-N modified layer contains Mo-N coating on subsurface and diffusion layers between the subsurface and substrate. The X- ray diffraction analysis of the Mo-N modified Ti6Al4V alloy reveals that the outmost surface of the Mo-N modified Ti6Al4V alloy is composed of phase Mo2N （fcc） and Mo2N （tetr）. The electrochemical corrosion performance of the Mo-N modified Ti6Al4V alloy in 0.5 mol/L HCl solution was investigated and compared with that of Ti6Al4V alloy. The chemical corrosion performance of the Mo-N modified Ti6Al4V alloy in boiling 37% HCl solution was investigated and compared with that of Ti6Al4V alloy. Results indicate that self-corroding electric potentials and corrosion-rate of the Mo-N modified Ti6Al4V alloy are higher than that of Ti6Al4V alloy in 0.5 mol/L HCl solution. The corrosion-rate of the Mo-N modified Ti6Al4V alloy is lower than that of Ti6Al4V alloy in boiling 37% HCl solution.     

非晶SiO2涂层的制备及其对Ti-22Al-26Nb合金的高温防护

以商业硅胶为原料,采用溶胶-凝胶法在Ti-22Al-26Nb合金表面浸涂制备非晶氧化硅涂层.涂层样品和空白样品在800和900℃静态空气中进行等温氧化实验,900℃静态空气中进行循环氧化实验.采用热重分析（TGA）、扫描电子显微镜（SEM）和X射线衍射（XRD）对结果进行分析,研究涂层对Ti-22Al-26Nb合金氧化行为的影响.结果表明：涂层样品的氧化抛物线速率常数较空白样品降低,涂层提高了合金在空气中的抗氧化能力.合金表面生成氧化膜主要由TiO2,Nb2TiO7和AlNbO4组成,涂层抑制了氧化物的生长.探讨了涂层的作用机制.     

Effects of Al addition on the microstructure and properties of Nb/Nb5Si3 in situ composites fabricated via spark plasma sintering

Dense Nb/Nb5Si3 composites were fabricated via spark plasma sintering technology using Nb, Si, and Al elemental powders as raw materials. The microstructttres of the synthesised composites were analyzed through scanning electron microscopy, X-ray diffraction, and electron probe microanalysis. The results show that the composites consisted of residual Nb particle phase and Nb5Si3 phase. The microstructure of the Nb/ Nb5Si3 in situ composites was evidently affected by Al addition, which prompted the formation of the Al3Nb10Si3 phase. In addition, the Rockwell hardness of the composites decreased with the increase in AI additions. The Rockwell hardness of Nb-20Si is 60HRC, which decreased to approximately 52.7 HRC when the Al content increased to 15 at%. The oxidation resistance of the Nb/NbsSi3 in situ composites significantly improved with the increase in Al addition.     

Nb质量分数对Al⁃15Si⁃xNb涂层组织与耐蚀性能的影响

以Al?15Si?xNb涂层为研究对象,探究了Nb质量分数对涂层显微组织结构和耐蚀性能的影响规律。采用金相显微镜观察涂层的组织形貌,运用XRD分析涂层的物相组成,应用电化学实验方法（包括开路电位、阻抗谱、极化曲线）表征并讨论了涂层在质量分数为3.5%的NaCl溶液中的腐蚀行为。结果表明,Al?15Si?xNb涂层主要由α?Al、初生Si、共晶Si组成,在涂层中加入Nb元素后生成少量的NbAl₃相和Nb₅Si₃相;Nb元素的加入促进异质形核,较明显地改变涂层的组织分布;Al?15Si?10Nb涂层中的组织更细小且分布更均匀,均匀分布的α?Al、初生Si和共晶Si构成众多均匀分布的腐蚀微电池,促进α?Al阳极反应,使涂层表面生成的Al₂O₃氧化膜更加连续;Al?15Si?xNb涂层的极化曲线具有类钝化特征,其中Nb质量分数为10%时涂层的自腐蚀电位和点蚀电位较高,产物膜电阻较大,维钝电流密度较低,具有更好的耐腐蚀性能。     

Surface morphology and electrochemical behaviour of Ti-48Al-2Cr-2Nb alloy in low-concentration salt solution

Electrochemical machining(ECM) is becoming increasingly important for the efficient machining of parts with a large machining area. This is an addition challenge for ECM because of the very high machining current. To overcome this difficulty, a direct and effective strategy is to adopt the machining mode that uses a low-concentration electrolyte with a low current density.The purpose of this study is to reveal the electrochemical behaviour and surface morphology in low-concentration electrolyte.The polarization behavior of Ti-48Al-2Cr-2Nb is measured by linear sweep voltammetry and cyclic voltammetry curves. The ηω-j curves demonstrate the special dissolution behaviour of Ti-48Al-2Cr-2Nb at low current densities. The surface morphology,surface quality, and dissolution mechanism are analysed in three low-concentration electrolytes at different current densities after the ECM dissolution experiments. The results demonstrate that Ti-48Al-2Cr-2Nb exhibits three unique dissolution morphologies in the three solutions, and we found that the γ-TiAl phase dissolves faster than the α_2-Ti_3Al phase. These results also show that 1% NaCl solution is more suitable for Ti-48Al-2Cr-2Nb in ECM compared with the other two solutions, considering its good surface quality, low breakdown potential, and high material removal rate. Later, the dissolution process of the sample in 1% NaCl solution at different corrosion times is revealed. Moreover, a dissolution model is proposed for the electrochemical dissolution behaviour of Ti-48Al-2Cr-2Nb in 1% NaCl solution.     

Solidification structures of high niobium containing TiAl alloys

To understand the effect of alloy stoichiometry on the microstructural development and mechanical behavior of γ-TiAlbased materials, it is necessary to have a determination of the phase relationships for the TiAl alloy system near the γ phase field.Cast structures and phases of Ti-(43-47)Al-8Nb-(1-2)Mn (at%) alloys have been studied by using scanning electron microscope and X-ray diffraction. Their solidification path and microstructure development during the solidification were analyzed. The experimental results show that the alloys with different Al contents form different macrostructures and microstructural morphologies. This indicates that the solidification paths are different with different Al contents. The alloy with 43Al forms equiaxed grain structure, and the solidification path is as follows: L → L β→β→α β→α β cores →α2 γ B2 cores. Whereas the alloy with 47Al forms columnar grain structure, and the solidification path is as follows: L → L β→α β L →α γ β cores →α2 γ B2 cores. The β phase is their primary solid phase and can be retained to ambient temperature. The alloy with 43Al solidifies completely into β phase. The peritectic reactions L β→α and L α→γ appear when the Al content increases to 47Al.     

熔体温度处理对磷铜变质Al-20%Si组织的影响

研究熔体温度处理工艺（包括熔体混合及熔体过热处理）与磷铜变质对Al-20%Si合金中硅相形态的影响。结果表明：在本试验条件下,单纯添加磷铜变质剂的Al-20%Si合金,当添加其合金质量的0.4%时,初晶硅由未变质前的97μm减小到65μm,减小了33%;当将熔体温度处理工艺与磷变质处理相结合时,此时Al-20%Si合金中的初晶硅尺寸减小至36μm,减小了62%,且钝化现象显著,弥散分布于α-Al基体上,共晶硅也由未变质前的长针状变为短纤维状和点状。     

CO_2激光熔覆镍基合金粉末的组织和性能

为了提高核发电成套设备的阀体性能,采用CO_2激光器在SUS316LN奥氏体不锈钢表面熔覆了镍基合金粉末.利用光学显微镜、扫描电子显微镜、电子探针分析仪、X射线衍射仪、能谱分析仪、显微硬度计和磨损试验机等对熔覆层的组织和性能进行了研究.结果表明,从熔覆层熔合线到表面的组织依次由平面晶生长区、亚共晶区,共晶区与过共晶区组成.亚共晶组织的初晶相由γ-Ni相组成,而过共晶组织的初晶相由Cr B和Cr7C3相组成.CO_2激光熔覆层具有较高的维氏硬度和耐磨性能,且其裂纹断口形貌属于解理断裂.