Mg粉和Zn粉烧结形成金属间化合物的研究

采用粉末烧结的方法制备Mg-Zn烧结体,利用光学和电子显微镜观察了Mg粉和Zn粉扩散反应区域的形貌,X射线衍射和能谱技术分析了该扩散反应区域的相组成;依据TFDC电子理论对扩散反应区域中金属间化合物的形成机制进行了讨论.研究发现,Mg粉和Zn粉在200 ℃,30 h的烧结过程中,Zn原子不断扩散进入到Mg晶体中,在Mg粉和Zn粉颗粒界面处,先后依次形成MgZn,MgZn2和Mg7Zn3 3种金属间化合物.     

Au-19.25Ag-12.80Ge钎料的焊接性能研究

根据Au-Ag-Ge三元相图, 制备了新型Au-19.25Ag-12.80Ge(%, 质量分数)钎料合金.利用DTA, Sirion200场发射扫描电镜对钎料的熔化特性及显微组织进行分析, 并对其与纯Ni的润湿性加以研究.结果表明: Au-19.25Ag-12.80Ge钎料合金的熔化温度为446.76～494.40 ℃, 结晶温度区间为47.64 ℃; 焊接温度在510～550 ℃范围内时, Au-19.25Ag-12.80Ge钎料合金与Ni基体具有良好的铺展性和润湿性, 在熔化钎料前沿有润湿环现象出现, 钎料合金与Ni基体之间形成了一条连续的金属间化合物层, 能谱分析表明该金属间化合物层为Ge3Ni5金属间化合物, 由于该化合物层较脆, 故应控制焊接工艺以获得连续均匀且厚度适当的金属间化合物层; 对于本钎料合金而言, 焊接温度530 ℃, 保温时间10 min可获得较理想的焊接界面.     

温度对Ag颗粒增强SnCu基复合钎料蠕变性能的影响

采用1 mm2微型单搭接钎焊接头, 研究了恒定应力下温度对Ag颗粒增强SnCu基复合钎料钎焊接头蠕变寿命的影响, 研究结果表明： 增强颗粒Ag与基体会发生冶金反应, 在Ag颗粒周围形成了一薄层Ag-Sn金属间化合物, 使增强颗粒Ag与基体紧密结合, 从而使复合钎料钎焊接头蠕变寿命优于基体SnCu钎料;温度对复合钎料钎焊接头蠕变寿命影响较SnCu钎料明显.     

硅对热浸镀ZnAl4合金镀层组织及生长动力学的影响

采用热浸镀法在纯铁片表面制备锌铝合金镀层,研究纯铁片在锌铝熔池(ZnAl4)中的界面反应,分析熔池中添加硅元素对镀层组织与生长动力学的影响。结果表明:随热镀时间延长,锌铝凝固组织与基体间的金属间化合物层(即中间合金层)的厚度增加。熔池中加入0.15%Si时,铁铝金属间化合物层的生长受到抑制,厚度减小,特别是在600℃时厚度减小更明显。Si在金属间化合物层中富集,使Fe和Al原子通过液相通道相互扩散受到阻碍,铁铝抑制层稳定存在,从而降低金属间化合物层的厚度。熔池中硅含量增加至0.30%时,对于铁锌合金层的抑制作用消失,合金层结构与不含硅时相似,形成Fe_2Al_5/FeAl_3/(Zn-Al)液相凝固组织。中间合金层的厚度随时间延长呈抛物线增长,表明镀层的形成受扩散控制;但适量硅在中间合金层的溶解能阻碍铁锌原子的扩散,从而抑制镀层过度生长。     

FeAl金属间化合物粉末注射成形工艺研究

通过机械合金化制备Fe-48at%Al金属间化合物粉末,分别按照33%、40%和50%的粉末装载量(体积分数)进行注射成形,成形坯经溶剂脱脂和热脱脂以及1 200℃真空烧结,得到FeAl金属间化合物.重点研究粉末装载量对喂料混炼、注射成形温度及压力、脱脂率及烧结组织和力学性能的影响.结果表明,机械合金化FeAl粉末由于具有不规则形状和层片结构,其注射成形喂料流动性较差;在使用高粉末装载量时应提高注射温度和压力,且溶剂脱脂率较低(7 h后为94.3%),需进一步延长脱脂时间;FeAl金属间化合物烧结试样的相对密度和抗弯强度均随粉末装载量增大而提高,当粉末装载最为50%,注射温度和注射压力分别为154℃和4.0 MPa时,材料的相对密度为92%,抗弯强度达587 MPa.     

铌合金表面辉光等离子渗Mo的扩散研究

利用辉光等离子表面冶金技术在Nb521合金表面制备了Mo合金层,研究了渗Mo过程中的扩散行为:主要分析了渗金属温度,保温时间对渗层厚度和扩散速率的影响。采用扫描电子显微镜(SEM)观察渗层表面、截面形貌,X射线能谱仪(EDS)检测渗层界面元素分布。实验结果表明,渗层由扩散层和沉积层组成,且组织致密,颗粒细小,无明显显微裂纹等缺陷,与基体结合良好。温度是影响扩散速率的最主要因素,随着温度的升高,扩散速率逐渐增加,而保温时间对扩散速率的影响不大。最佳工艺下,渗层厚度可达26.5μm,扩散层厚度可达6.89μm,扩散速率可达1.73μm.h-1,Mo元素含量从表面到心部呈梯度分步,在涂层与基体的界面处,钼铌原子发生了不同程度的互扩散。最后依据传统扩散理论计算得到了Mo在不同实验温度下的扩散系数,并拟合得到了离子轰击作用下Mo在Nb521合金中的扩散激活能为292 k.Jmol-1。     

热浸镀5%Al-Zn合金钢板金属间化合物的形成及其对涂层显微结构的影响

该项研究系由我国台湾省台南市的一大学的材料工程系完成。研究了热浸镀5％Al一Zn钢板时，镇液温度（在金属间化合物形成区间的温度）的变化，对涂层显微组织的影响情况。研究表明，当浸镀液温度高于18OC，钢板浸镀lmin时，所得的镀层外表面粗糙。将镀液温度降至‘16OC，但延长浸镀时间至5n。in以上时，镀层外表面亦很粗糙。电子显微镜检测结果表明，粗糙的外表是由于涂层中相应生成了铁～锡金属间化合物。c18oC以上温度浸镇时，涂层晶粒长大快，这与此时金属间化合物快速形成密切相关，金属间化合物层的厚度可达整个涂层厚的7O％。热浸…     

Ti-55531合金片层组织的表层渗硼改性研究

系统研究了不同温度渗硼处理对Ti-55531片层合金表层组织、成分、硬度分布及残余应力的影响。结果表明：Ti-55531合金渗硼后渗层由等轴化趋势明显的白亮产物外表层、须状组织过渡层和原始片层基体三部分组成,渗层B元素含量由表及里逐渐降低。合金表层因渗硼后形成了钛硼化合物梯度层,显微硬度得到显著提高,且从表层到心部硬度也逐渐降低。另外,渗硼后合金表面呈现为残余压应力状态,且残余压应力值随渗硼温度的升高而增大。本研究结果可为进一步研究渗硼处理对Ti-55531合金耐磨损及疲劳性能的影响奠定基础。     

渗铝低碳带钢的合金化反应

由于在表面形成稳定的氧化膜而使铝化钢有极好的抗氧化性,因此,常用于在高温环境下的部件,当铝化钢加热到873K以上时,涂层和钢基之间产生扩散,结果涂层变为由几种金属间化合物组成的混合层。在本研究中,铝化钢在873K温度下保温不同时间,用SEM—EDS分析了每一试样表面形成层的成分,每一层分析的成分与由热力学计算的Al—Fe—Si相图进行比较,以确定每一层的不同,在873K温度下检测了铝化层与钢基之间的扩散途径,观察到金属间化合物层的中间层中的Al含量比其它层中的低,由铝化层的成分判断,是由相互作用的两相细晶混合物组成。TEM—EDS分析表明铝化层是由Fe2Al5和T1两相混合组成。     

W-Mo-Ni-Fe重合金金属间化合物相析出机制研究

为了分析Mo元素含量对液相烧结W—Ni—Fe重合金显微组织的影响和探讨Mo元素含量与基地相、析出相等各相组成的关系，以及了解合金于炉冷后在固相与基地相接口析出的金属间化合物相之形成机制，本研究使用具有相同基地相组成但不同Mo元素含量(Mo的原子数分数为15％～59％)的试片，以SEM、EMPA观察显微组织的变化，并使用XRD对金属间化合物析出相进行结构分析与鉴定，最后再以DTA热分析仪器量测合金的相变化温度，以厘清金属间化合物相的析出机制。试验结果显示，当合金中含有高比例的Mo元素时，烧结后在基地相中固溶的Mo元素与W Mo元素总和将随之升高，除了造成基地相的凝固温度下降以外，也形成大量的(W，Mo)0.5-(Ni，Fe)0.5 x(z=0～0．04)金属间化合物析出相，而此金属间化合物相中，Mo元素所占的比例会随着添加的Mo元素比例增加而呈线性上升。热分析结果显示，金属间化合物相的析出温度大约是在1349～1355℃之间，而基地相的凝固温度则从1415℃降低到1336℃。根据这些现象可以了解，金属间化合物相的形成机制与合金成分中的MMo／(Mw MMo)比值有关，当比值高于0．66时，金属间化合物相的析出机制为偏晶反应(monotectic reaction)；当比值在0．5～0．66之间时，析出机制是属于共晶反应(eutectic reaction)；当比值在0．34～0．5之间时，析出机制可能是共析反应(eutectoid reaction)或者是包析反应(peritectoid reaction)；比值低于0．2时，则不会析出金属间化合物相。     

Regularities of Reactive Diffusion and Phase Formation in Ni ― Bi,Ni ― Zn,and Co ― Zn Binary Systems

Intermetallide layers enriched in bismuth or zinc are the first to grow in the Ni Bi, Ni Zn, and Co Zn reaction pairs. It is not found that high-symmetry phases of equiatomic composition are formed. There is not even a weak correlation between the rate of layer growth and the width of the homogeneity region for these intermetallic compounds. The main factors that determine the formation sequence for the intermetallic layers are the differences in melting point and atomic radius between the components, as well as the crystal structures of the intermetallides. The Kirkendall effect cannot be observed in the growing intermetallic layers. In that case, there is no physical basis for determining integrated diffusion coefficients.     

Influence of Chemical Composition of Mg Alloys on Surface Alloying by Diffusion Coating

A recently developed technique of surface alloying by diffusion-coating has been used to produce coatings on Mg alloys with various Al and Zn contents. The experimental results show that both Al and Zn solutes in the alloy promote the diffusion of alloying elements through grain refinement of the substrate alloys and through reduction of diffusion active energy because of the reduction of melting temperature of the alloys. Therefore, the efficiency of surface alloying increases by diffusion coating. Thick, dense, uniform, and continuous layers of intermetallic compounds, which consist of a τ-phase layer and a β-phase layer, can be produced on the surface of various Mg alloys. The intermetallic compound layers not only have microhardness values that are 4 to 6 times higher than the substrate but also provide effective protection of the Mg alloys from corrosion in 5 pct NaCl solution at room temperature.     

还原扩散法直接制备YFe4金属间化合物粉末

通过实验和样品检测 ,分析了还原扩散法直接制备 YFe4 金属间化合物粉末的高温形成过程。     

Galvalume镀层金属间化合物层的生长及缺陷研究

通过分析热浸镀Galvalume镀层金属间化合物层的生长和缺陷,发现短时间的热浸镀,钢基表面能形成完整的金属间化合物层,形成的金属间化合物层均由铁铝化合物相（Fe2A15、FeAl3）和T5相两层组成。随着浸镀时间的延长,清晰可见Fe2A15、FeAl,和T5三个相层。在长时间的热浸镀过程中,钢基不断被铝锌液侵蚀。在生产过程中,镀层金属间化合物层存在大量的缺陷,将加剧铝锌液对钢基的侵蚀,甚至导致钢基剥落。     

Rate of dissolution of solid nickel in liquid tin under static conditions

The dissolution kinetics of solid nickel in liquid tin have been investigated under static conditions. The cylindrical nickel specimens were immersed in liquid tin over the temperature range of 551 to 803 K in the reaction time range of 0.9 to 6.0 ks. A natural convection model for mass transfer and the dissolution rate equation derived by considering intermetallic compound layer formation were used to interpret the experimental dissolution data. A larger dissolution at the upper part of specimen causing natural convection and an intermetallic layer formation with a linear relationship at solid/liquid interface occurred. Below 628 K, the dissolution rate appears to be controlled by chemical reaction of an intermetallic compound layer. At mid-range temperatures (of 681 K), the dissolution process was governed by a mixed control mechanism involving diffusion in liquid tin and chemical reaction of the intermetallic compound layer. At temperatures above 735 K, the rate seems to be controlled by diffusion across a concentration boundary layer in liquid tin. The formation of an intermetallic compound layer did not interfere with the dissolution.     

Die soldering: Mechanism of the interface reaction between molten aluminum alloy and tool steel

Die soldering is the result when molten aluminum sticks to the surface of the die material and remains there after the ejection of the part; it results in considerable economic and production losses in the casting industry, and is a major quality detractor. In order to alleviate or mitigate die soldering, one must have a thorough understanding of the mechanism by which the aluminum sticks to the die material. A key question is whether the die soldering reaction is diffusion controlled or interface controlled. A set of diffusion couple experiments between molten aluminum alloy and the ferrous die was carried out. The results of the diffusion couple experiments showed that soldering is a diffusional process. When aluminum comes in contact with the ferrous die material, the iron and the aluminum atoms diffuse into each other resulting in the formation of a series of intermetallic phases over the die material. Initially iron and aluminum react with each other to form binary iron-aluminum intermetallic phases. Subsequently, these phases react with the molten aluminum to further form ternary iron-aluminum-silicon intermetallic phases. Iron and aluminum have a great affinity for each other and the root cause of die soldering is the high reaction kinetics, which exists between iron and aluminum. Once the initial binary and ternary intermetallic phase layers are formed over the die material, the aluminum sticks to the die due to the abnormally low thermal conductivity of the intermetallic phases, and due to favorable interface energies between the intermetallic layers and aluminum. The experimental details, the results of the interface reactions, and the analysis leading to the establishment of the mechanism giving rise to die soldering are reviewed discussed.     

623K温度下SnxZn1-x/Ni扩散偶的界面反应

为研究Sn-Zn合金(无铅焊料的候选者)和Ni基体(Cu基上的扩散阻挡层)的界面反应,制备一系列原子分数x分别为14.8％、22％和31％的液固扩散偶Sn1-xZnx/Ni;在623 K温度下恒温退火后,用扫描电镜和电子探针检测与分析扩散偶的界面结构,研究退火时间和合金中的Zn含量对扩散层结构和形貌的影响.结果表明,S...     

Change Rules of Γ_2 Particles in Hot-dipped Zn-Ti Coating

Hot-dip Zn-Ti galvanizing can restrain the excess growth of the coating which has better corrosion resistances than hot-dip pure Zn.The change rules ofΓ2intermetallic compound in hot-dip Zn-Ti galvanizing is investigated by immersion time,titanium content and the slag test using scanning electron microscopy(SEM),energy dispersive spectroscopy(EDS)and X-ray diffraction(XRD).And the mechanism of nucleation and growth ofΓ2intermetallic compound is analysed.The results show that,when adding 0.05mass%titanium to the zinc bath,theΓ2particles form in theηlayer,which nucleate by obtaining Ti atoms from theηphase and Fe atoms from the dissolvingζphase layer.Moreover,the more titanium is added into the bath,the more and biggerΓ2 particles appear.TheГ2particles in the coatings grow up noticeably with prolonging the immersion time.     

Electrode Process of Y~(3 ) Ion on Copper Electrode and Surface Alloying

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镍基高温合金液相扩散焊接头组织及性能

镍基高温合金GH4413在高温下具有较为优异的高温持久强度和抗蠕变性能,在航空发动机和各种工业燃气轮机中得到广泛应用。以BNi 2作为填充合金材料使用液相扩散焊对GH4413合金进行了连接,研究了在焊接温度分别为1 030和1 080 ℃、保温时间分别为30和60 min等不同焊接参数下GH4413镍基高温合金的接头微观组织、成分分布和显微硬度。扫描电镜(SEM)以及能谱分析结果表明,当焊接温度为1 080 ℃、保温时间为60 min 时,钎缝组织中形成了性能良好的固溶体,且随着焊接温度的升高和保温时间的延长,钎缝的宽度增加,钎料元素向母材中的扩散深度逐渐增加,在母材近缝区形成了金属间化合物。