Fe3Al/Q235异种材料扩散焊界面相结构分析

采用X射线衍射、透射电镜和电子衍射技术对Fe3Al/Q235真空扩散焊界面附近的微观相结构进行了试验研究。试验结果表明，当加热温度1050～1080℃，保温时间60min，压力9.8MPa时，Fe3Al金属间化合物与Q235钢扩散焊界面附近形成了明显的扩散过滤区，该过渡区由Fe3Al相和a-Fe(Al）固深体构成，显微硬度约为480～540HM，不存在含铝校较高的高硬度脆性相。有利于提高Fe3Al/Q235扩散过滤区的韧性，提高扩散焊接头的抗裂纹能力。扩散过滤区中的Fe3Al相与a-Fe(Al）固溶体之间存在着（110）a-Fe(Al)//(011)Fe3Al和[001]a-Fe(Al)//[100]Fe3Al的晶体学取向关系。     

高速电弧喷涂Fe-Al/Cr3C2复合涂层的组织结构研究

采用粉芯丝材结合高速电弧喷涂(HVAS)技术原位合成了Fe-Al/Cr3C2复合涂层,使用SEM﹑TEM﹑X-Ray等手段研究了涂层的组织和相结构.结果表明,涂层机械结合紧密;涂层具有致密的层状结构,扁平颗粒小,氧化物膜细小,硬质点相分布均匀,孔隙率低;在涂层中存在着多种结构复杂的组织和化合物相,基体相FeAl和Fe3Al,硬质相Cr3C2、Fe3C及AlFe3C0.5,氧化物相FeO·Al2O3、Cr2O3;不同物质相之间存在着平行的晶体学取向关系,从而提高了涂层的力学性能.     

氩弧重熔对球墨铸铁热浸镀铝层组织和性能的影响

将球墨铸铁在780℃热浸镀铝后进行氩弧重熔处理,利用扫描电镜和X射线衍射仪对热浸镀铝层和氩弧重熔层组织进行观察,测定了氩弧重熔前后试件截面的显微硬度。结果表明:球墨铸铁热浸镀铝后,镀层由富铝层及扩散层构成,富铝层包含降温形成的针状FeAl3相,扩散层由FeAl3、Fe2Al5相组成,扩散层形状呈柱状延伸到基体中。热浸镀铝层经氩弧重熔处理后,试件由重熔层和过渡层及基体构成。重熔层由Al、Fe、C和FeAl3相组成,过渡层组织为马氏体+残留奥氏体+少量球状石墨。氩弧重熔处理能明显提高热浸镀铝层的显微硬度。重熔层硬度值可达900 HV,在过渡层硬度下降缓慢,直至基体。     

硅对45钢热浸镀铝层真空扩散处理显微组织的影响

利用扫描电镜和能谱分析手段研究了铝池中的硅对热浸镀铝层在真空高温扩散处理过程中的显微组织演变的影响。确定了扩散层的组成相,研究了镀层的生长动力学,讨论了扩散层空洞带的形成机理。研究表明,铝池中的硅能减少热浸镀铝层的厚度。在同样的扩散条件下硅的添加抑制了Fe2Al5的生长,促进了FeAl和富铝α-Fe层的生长。扩散处理时从含硅的Fe2Al5中容易析出τ1-（Al,Si）5Fe3相或FeAl相。硅的加入使得FeAl层和富铝α-Fe层间的空洞或晶间裂纹易于早期出现,但随着扩散时间的延长,又逐渐减小或消失。空洞的形成与消失与硅在FeAl层中的富聚有关。由于Fe2Al5相与其中析出的τ1-（Al,Si）5Fe3相发生包共晶反应,即：τ1＋Fe2Al5L＋FeAl,形成了不连续的外侧FeAl层。     

1Cr18Ni9Ti热浸镀铝扩散层的抗氧化性

通过高温氧化实验,测定出1Cr18Ni9Ti热浸镀铝前后的氧化增重,分析了扩散层的微观结构和表面氧化产物的物相组成.结果表明1Cr18Ni9Ti热浸镀铝后的抗氧化温度可达1100℃,扩散层中Fe2Al5退化成FeAl后,β-NiAl将发挥抗氧化作用,α-A12O3相的形成是使材料抗高温氧化性提高的主要原因.     

1Cr18Ni9Ti热浸镀铝扩散层的的抗氧化性

通过高温氧化实验,测定出1Cr18Ni9Ti热浸镀铝前后的氧化增重,分析了扩散层的微观结构和表面氧化产物的物相组成。结果表明：1Cr18Ni9Ti热浸镀铝后的抗氧化温度可达1100℃,扩散层中Fe2Al5退化成FeAl后β-NiAl将发挥抗氧化使用,α-Al2O3相的形成是使材料抗高温氧化性提高的主要原因。     

扩散处理热浸镀铝钢高温抗氧化行为的研究

对经不同扩散工艺处理的热浸镀铝层高温抗氧化性进行了研究,通过SEM、TEM、XRD分析了经扩散处理后,热浸镀铝层高温氧化过程中组织结构的变化情况,分析了热浸镀铝层高温抗氧化性能和微观结构的关系,确定了提高热浸镀铝层高温抗氧化性的适宜扩散温度.结果表明,经750℃扩散处理,热浸镀铝层结构由较厚的外表层(Fe2Al5+FeAl2)及内层(FeAl+条状FeAl2)组成,条状FeAl2的形成为氧提供了扩散通道,其抗氧化性较差;经950℃扩散处理,镀层外表层变薄,外表层转为单一FeAl2、内层为FeAl,并出现早期内氧化裂纹,其抗氧化性较差:当扩散处理温度为850℃时,镀层外表层变薄,结构转为FeAl2+少量Fe2Al5,而内层增厚,其结构为FeAl+球状FeAl2,而内层FeAl2球化,增强了氧由内层向基体扩散的阻碍作用,使氧只能逐层形成Al2O3+Fe2O3的氧化膜,提高了镀层的高温抗氧化性.     

扩散处理热浸镀铝钢高温抗氧化行为的研究

对经不同扩散工艺处理的热浸镀铝层高温抗氧化性进行了研究,通过SEM、TEM、XRD分析了经扩散处理后,热浸镀铝层高温氧化过程中组织结构的变化情况,分析了热浸镀铝层高温抗氧化性能和微观结构的关系,确定了提高热浸镀铝层高温抗氧化性的适宜扩散温度.结果表明,经750℃扩散处理,热浸镀铝层结构由较厚的外表层(Fe2Al5+FeAl2)及内层(FeAl+条状FeAl2)组成,条状FeAl2的形成为氧提供了扩散通道,其抗氧化性较差;经950℃扩散处理,镀层外表层变薄,外表层转为单一FeAl2、内层为FeAl,并出现早期内氧化裂纹,其抗氧化性较差当扩散处理温度为850℃时,镀层外表层变薄,结构转为FeAl2+少量Fe2Al5,而内层增厚,其结构为FeAl+球状FeAl2,而内层FeAl2球化,增强了氧由内层向基体扩散的阻碍作用,使氧只能逐层形成Al2O3+Fe2O3的氧化膜,提高了镀层的高温抗氧化性.     

扩散退火对球墨铸铁热浸镀铝组织的影响

为了研究扩散退火对铸铁热浸镀铝工艺的影响,以球墨铸铁为基体进行热浸镀铝,对浸镀层截面进行了形貌观察(SEM)、能谱分析(EDS)和衍射分析(XRD),分析了扩散退火对镀层组织的影响.结果表明:浸镀层由表面富铝层及扩散层构成,富铝层包含降温形成的针状FeAl3相,扩散层由FeAl3、Fe2Al5相组成,形状如舌状指向基体.850℃扩散退火,随扩散时间的延长镀层组织结构明显变化.试验结果表明:耐热用热浸镀铝件在使用前进行扩散退火处理是可行的.     

铝膜的低价硫化铝歧化反应制备法

对用低价硫化铝的歧化反应进行钢基镀膜作了定性研究。用两种蒸发源(2Al2O3 6C Al2S3)和(4Al Al2S3)分别进行反应蒸发镀膜，系统真空度为5Pa左右，基材温度为1100℃。研究结果表明：以(2Al2O3 6C Al2S3)为蒸发源的钢基镀膜层为α-Fe及Al13Fe4相，对硝酸酒精溶液具有抗蚀性好的特点，但其平整性稍差，扩散层薄；以(4Al Al2S3)为蒸发源的镀膜层为Fe3Al及AlFe相，其镀膜层表面光滑，平整，扩散层厚等特点。     

Effects of Post-weld Heat Treatment on Microstructure,Mechanical Properties and the Role of Weld Reinforcement in 2219 Aluminum Alloy TIG-Welded Joints

In as-welded state, each region of 2219 aluminum alloy TIG-welded joint shows diff erent microstructure and microhardness due to the diff erent welding heat cycles and the resulting evolution of second phases. After the post-weld heat treatment, both the amount and the size of the eutectic structure or θ phases decreased. Correspondingly, both the Cu content in α-Al matrix and the microhardness increased to a similar level in each region of the joint, and the tensile strength of the entire joint was greatly improved. Post-weld heat treatment played the role of solid solution strengthening and aging strengthening. After the post-weld heat treatment, the weld performance became similar to other regions, but weld reinforcements lost their reinforcing eff ect on the weld and their existence was more of an adverse eff ect. The joint without weld reinforcements after the post-weld heat treatment had the optimal tensile properties, and the specimens randomly crack in the weld zone.     

The First Phase of the SRIF Industrialized Base in ＂West Area＂ Has Been Put into Operation

After nearly two years＇ tense construction, the first phase of industrialized base of Shenyang Research Institute of Foundry （SRIF）, located at the Tiexi Casting and Forging Industrial Park in the west of Tiexi District, has now been completed and formally put into operation.     

Thermodynamics Study on the Decomposition of Chromite with KOH

Institute of Process Engineering, Chinese Academy of Sciences, China, has proposed a method for oxidative leaching of chromite with potassium hydroxide. Understanding the mechanism of chromite decomposition, especially in the potassium hydroxide fusion, is important for the optimization of the operating parameters of the oxidative leaching process. A traditional thermodynamic method is proposed and the thermal decomposition and the reaction decomposition during the oxidative leaching of chromite with KOH and oxygen is discussed, which suggests that chromite is mainly destroyed by reactions with KOH and oxygen. Meanwhile, equilibrium of the main reactions of the above process was calculated at different temperatures and oxygen partial pressures. The stable zones of productions, namely, K2CrO4 and Fe2O3, increase with the decrease of temperature, which indicates that higher temperature is not beneficial to thermodynamic reactions. In addition, a comparison of the general alkali methods is carried out, and it is concluded that the KOH leaching process is thermodynamically superior to the conventional chromate production process.     

Influence of Heat Treatment on Damping Behaviour of the Magnesium Wrought Alloy AZ61

The effect of isochronal heat treatments for 1h on variation of damping, hardness and microstructural change of the magnesium wrought alloy AZ61 was investigated. Damping and hardness behaviour could be attributed to the evolution of precipitation process. The influence of precipitation on damping behaviour was explained in the framework of the dislocation string model of Granato and Lücke.     

Effect of Rare Earth Doping on Impedance,Modulus and Conductivity Properties of Multiferroic Composites:0.5(BiLa_xFe_(1-x)O_3)–0.5(PbTiO_3)

The Lanthanum-doped bismuth ferrite–lead titanate compositions of 0.5(Bi LaxFe1-xO3)–0.5(Pb Ti O3)(x = 0.05,0.10,0.15,0.20)(BLxF1-x-PT) were prepared by mixed oxide method.Structural characterization was performed by X-ray diffraction and shows a tetragonal structure at room temperature.The lattice parameter c/a ratio decreases with increasing of La(x = 0.05–0.20) concentration of the composites.The effect of charge carrier/ion hopping mechanism,conductivity,relaxation process and impedance parameters was studied using an impedance analyzer in a wide frequency range(102–106Hz) at different temperatures.The nature of Nyquist plot confirms the presence of bulk effects only,and non-Debye type of relaxation processes occurs in the composites.The electrical modulus exhibits an important role of the hopping mechanism in the electrical transport process of the materials.The ac conductivity and dc conductivity of the materials were studied,and the activation energy found to be 0.81,0.77,0.76 and 0.74 e V for all compositions of x = 0.05–0.20 at different temperatures(200–300 °C).     

Quantitative Analysis of the Crystallographic Orientation Relationship Between the Martensite and Austenite in Quenching–Partitioning–Tempering Steels

The orientation relationships(ORs)between the martensite and the retained austenite in low-and medium-carbon steels after quenching–partitioning–tempering process were studied in this work.The ORs in the studied steels are identified by selected-area electron diffraction(SAED)as either K–S or N–W ORs.Meanwhile,the ORs were also studied based on numerical fitting of electron backscatter diffraction data method suggested by Miyamoto.The simulated K–S and N–W ORs in the low-index directions generally do not well coincide with the experimental pole figure,which may be attributed to both the orientation spread from the ideal variant orientations and high symmetry of the low-index directions.However,the simulated results coincide well with experimental pole figures in the high-index directions{123}_(bcc).A modified method with simplicity based on Miyamoto’s work was proposed.The results indicate that the ORs determined by modified method are similar to those determined by Miyamoto’method,that is,the OR is near K–S OR for the low-carbon Q–P–T steel,and with the increase of carbon content,the OR is closer to N–W OR in medium-carbon Q–P–T steel.     

Growth Kinetics of Single Inclusion Particle in Molten Melts

On the basis of the single-particle framework, a new theory on inclusion growth in metallurgical melts is developed to study the kinetics of inclusion growth on account of reaction and collision. The studies show that the early growth of inclusion depends on reaction growth and Brawnian motion collision, and where the former is decisive, the late growth depends on turbulence collision and Stokes＇ collision, and where the former is dominant; collision growth is very quick during the smelting process, lessened in the refining process, but nearly negligible in the continuous casting process.     

Theoretical Analysis for the Motion and Temperature of Melt Droplets in Spray Degassing Process

The motion of melt droplets in spray degassing process was analyzed theoretically. The height of the treatment tank in spray degassing process could be determined by the results of theoretical calculation of motion of melt droplets. To know whether the melt droplets would solidify during spraying process, the balance temperature of melt droplets was also theoretically analyzed. Then proof experiments for theoretical results about temperature of melt droplets were carried. In comparison, the experimental results were nearly similar to the calculation results.     

Using Finite Element and Contour Method to Evaluate Residual Stress in Thick Ti-6Al-4V Alloy Welded by Electron Beam Welding

This work was to reveal the residual stress profile in electron beam welded Ti-6Al-4V alloy plates(50 mm thick) by using finite element and contour measurement methods.A three-dimensional finite element model of 50-mmthick titanium component was proposed,in which a column–cone combined heat source model was used to simulate the temperature field and a thermo-elastic–plastic model to analyze residual stress in a weld joint based on ABAQUS software.Considering the uncertainty of welding simulation,the computation was calibrated by experimental data of contour measurement method.Both test and simulated results show that residual stresses on the surface and inside the weld zone are significantly different and present a narrow and large gradient feature in the weld joint.The peak tensile stress exceeds the yield strength of base materials inside weld,which are distinctly different from residual stress of the thin Ti-6Al-4V alloy plates presented in references before.     

Microstructures and Tensile Properties of Ultrafine-Grained Ni–(1–3.5) wt% SiC_(NP) Composites Prepared by a Powder Metallurgy Route

Silicon carbide nanoparticle-reinforced nickel-based composites(Ni–Si CNP),with a Si CNPcontent ranged from1 to 3.5 wt%,were prepared using mechanical alloying and spark plasma sintering.In addition,unreinforced pure nickel samples were also prepared for comparative purposes.To characterize the microstructural properties of both the unreinforced pure nickel and the Ni–Si CNPcomposites transmission electron microscopy(TEM) was used,while their mechanical behavior was investigated using the Vickers pyramid method for hardness measurements and a universal tensile testing machine for tensile tests.TEM results showed an array of dislocation lines decorated in the sintered pure nickel sample,whereas,for the Ni–Si CNPcomposites,the presence of nano-dispersed Si CNPand twinning crystals was observed.These homogeneously distributed Si CNPwere found located either within the matrix,between twins or on grain boundaries.For the Ni–Si CNPcomposites,coerced coarsening of the Si CNPassembly occurred with increasing Si CNPcontent.Furthermore,the grain sizes of the Ni–Si CNPcomposites were much finer than that of the unreinforced pure nickel,which was considered to be due to the composite ball milling process.In all cases,the Ni–Si CNPcomposites showed higher strengths and hardness values than the unreinforced pure nickel,likely due to a combination of dispersion strengthening(Orowan effects) and particle strengthening(Hall–Petch effects).For the Ni–Si CNPcomposites,the strength increased initially and then decreased as a function of Si CNPcontent,whereas their elongation percentages decreased linearly.Compared to all materials tested,the Ni–Si CNPcomposite containing 1.5% Si C was found more superior considering both their strength and plastic properties.