铁基合金激光熔覆组织及高温时效转变的TEM研究

利用ＡＴＥＭ研究了铁基金元合金Ｆｅ－Ｃｒ－Ｗ－Ｎｉ－Ｃ激光熔覆层的微观组织,亚稳相结构特征以及高温时效时的亚相变转机制。结果表明组织为亚共晶组织,即γ＋（γ＋ＭＣ）,γ－奥氏体为具有较高合金度的过饱和亚稳相,Ｍ７Ｃ３（Ｍ为Ｃｒ,Ｆｅ,Ｗ）为六方结构的Ｃｒ基亚稳合金碳化物。     

铁基合金激光熔覆组织及高温时效转变的TEM研究

利用ＡＴＥＭ研究了铁基多元合金ＦｅＣｒＷＮｉＣ激光熔覆层的微观组织、亚稳相结构特征以及高温时效时的亚稳相转变机制。结果表明组织为亚共晶组织,即γ＋（γ＋Ｍ７Ｃ３）,γ奥氏体为具有较高合金度的过饱和亚稳相,Ｍ７Ｃ３（Ｍ为Ｃｒ,Ｆｅ,Ｗ）为六方结构的Ｃｒ基亚稳合金碳化物。熔覆组织在高温时效时存在两类碳化物形成机制,即亚稳γ中析出Ｍ２３Ｃ６、Ｍ２Ｃ与ＭＣ碳化物以及Ｍ７Ｃ３→Ｍ２３Ｃ６与Ｍ７Ｃ３→Ｍ６Ｃ的碳化物原位转变机制。熔覆组织具有较高的显微硬度并存在显著的二次硬化特征     

激光熔覆Co基合金＋W工艺与组织结构特征研究

利用２ｋＷ的ＣＯ２激光器在Ｑ２３５钢表面熔覆Ｃｏ基合金＋Ｗ混合粉末,能够获得外观质量良好的熔覆层。激光熔覆所需最小比能随Ｗ含量的增加而增大。熔覆层的组织由γ‘－Ｃｏ枝状晶及枝晶间γ’－Ｃｏ和Ｍ７Ｃ３共晶组成,没有发现Ｗ颗粒。分析结果表明,Ｗ颗粒在Ｃｏ基合金熔体中溶解,并在Ｃｏ基合金凝固后固溶于γ‘－Ｃｏ。由于Ｗ溶解反应有热,因而使激光熔覆所需能量增加。     

超硬质相在高温磨损中的行为及抗磨性

通过高温硬度、高温磨损试验,研究了铁基Ｃｒ－Ｍｏ－Ｗ－Ｖ－Ｎｂ系高温耐磨料磨损等离子弧粉末堆焊合金,可以替代价格昂贵的镍基和然基等离子弧堆焊合金。同时系统地研究了合金元素及其硬质相在高温磨损中的行为及堆焊合金抗磨性。即Ｃｒ７Ｃ３「（Ｃｒ,Ｆｅ）７Ｃ３」、ＣｒｅＣ「（Ｃｒ,Ｆｅ）３Ｃ」、ＷＣ、Ｗ２Ｃ、ＮｂＣ、Ｖｃ硬质相对堆焊层的组织、硬度和耐磨性的影响规律。结果表明：硬质相的形态、数据和大小不同对堆     

激光熔覆Ni—Cr—B—Si—C合金的组织及其摩擦磨损特性

运用ＳＥＭ,ＴＥＭ及ＸＲＤ研究了优化工艺条件下获得的激光熔覆Ｆ１０２ＮｉＣｒＢＳｉＣ合金粉末涂层的微观组织。结果表明,涂层区组织为初生铬硼化合物＋Ｎｉ基胞枝状固溶体＋Ｎｉ枝晶间析出的碳化物、硼化物和Ｎｉ＋Ｎｉ３Ｂ或Ｎｉ＋Ｍ２３Ｃ６;结合区组织为以Ｎｉ＋Ｎｉ３Ｂ为主及碳化物和碳硼化物构成的伪多元共晶胞状晶。摩擦磨损试验表明,激光涂层的摩擦系数（０．２１～０．３）比钢基底（０．６５～０．８）低得多,磨损速率约低一个数量级。     

非晶态Fe—W镀层铬酸盐钝化膜耐蚀机理探讨

Ｆｅ－Ｗ非晶镀层经铬酸盐钝化处理，可获得有装饰的含Ｃｒ钝化膜，经测定，孔蚀电位较钝化前正移１．６８Ｖ，明显改善了抗Ｃｌ＾－腐蚀的能力，ＡＥＳ与ＸＰＳ的分析结果表明，钝化膜由内外两层构成，外层为Ｆｅ（ＣｒＯ４）３．Ｃｒ２（ＣｒＯ４）３／Ｃｒ２（Ｃｒ２Ｏ７）３．Ｆｅ（ＯＨ）３／ＦｅＯＯＨ．ＷＯ３．ｎＨ２Ｏ等化合物，内层由Ｃｒ２Ｏ３，ＣｒＯ３，ＣｒＯＯＨ，ＦｅＯ，Ｆｅ２Ｏ３及ＷＯ３组成。钝化膜厚度约为６     

Fe－25Cr－9Mn三元合金高温硫化特性

研究了Ｆｅ－２５Ｃｒ－９Ｍｎ合金在８００℃、１０－３─１Ｐａ硫分压的Ｈ２－Ｈ２Ｓ混合气体中的硫化行为，并与Ｆｅ－２５Ｃｒ合金进行了对比。结果表明：Ｍｎ的加入提高了Ｆｅ－２５Ｃｒ合金的抗硫化性能，但作用并不显著。在Ｆｅ－２５Ｃｒ－９Ｍｎ合金的多层结构硫化层中形成了较厚且独立的α－（Ｍｎ．Ｆｅ）Ｓ层，但它并没有效地阻挡Ｆｅ２＋和Ｃｒ３＋向外的扩散。文中讨论了这种现象的原因以及硫化层分层对铁铬合金硫化行为的影响。     

不同钒,碳含量高速钢的凝固组织及相组成

利用热分析，Ｘ射线衍射和着色金相法详细研究了Ｆｅ－５Ｃｒ－５Ｍｏ－Ｔ２－Ｖ－Ｃ系合金中Ｖ和以Ｃ量对凝固过程中结晶相的种类和结晶温度的影响，得到了合金万分与凝固组织的关系，建立了（Ｆｅ－５Ｃｒ－５Ｍｏ－５Ｗ－２Ｃ）－Ｖ和（Ｆｅ－５Ｃｒ－５Ｍｏ－５Ｗ－３Ｖ）－Ｃ的准二元相图，以及（Ｆｅ－５Ｃｒ－５Ｍｏ－５Ｗ）－Ｖ－Ｃ合金的液相面投影图。     

合金元素对Zr—Sn—Fe—Cr—Nb合金性能的影响

介绍了几种新锆合金４００℃，１０．３ＭＰａ静态高压釜试验结果和室温及高温（３７５℃）的拉伸试验结果，分析了新合金中合金元素Ｎｂ．Ｓｎ．Ｆｅ．Ｃｒ对抗伸强度及耐蚀性能的影响。结果表明：通过控制合金元素的含量，在经历与Ｚｒ－４相同的生产工艺条件下、可以得到强度和耐蚀性能更为优异的新铝合金。试验表明：这种新型的Ｚｒ－Ｓｎ－Ｆｅ－Ｃｒ－Ｎｂ中加入Ｎｂ量应在０．１ｗｔ％－０．３ｗｔ％之间；在含１ｗｔ％Ｎｂ的新合金中，Ｓｎ的含量不应低于０．５ｗｔ％：在新合金研制时，适当提高Ｆｅ＋Ｃｒ的含量是有益的，但Ｆｅ／Ｃｒ比不应     

WC—高碳铬铸铁铸渗层耐磨性与显微结构的研究

在ＭＭ２００磨损试验机上研究了铸渗层的抗磨粒磨损性能。利用透射电镜研究了铸渗层的组织结构。研究结果表明,铸渗层的耐磨性比淬火态４５钢提高３倍,比ＱＴ６００－３提高４倍,渗层中块状颗粒ＷＣ和（Ｃｒ,Ｆｅ）７Ｃ３片状颗粒结合牢固,且（Ｃｒ,Ｆｅ）７Ｃ３颗粒中有孪晶,ＷＣ颗粒中有位错。     

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.