气流磨处理钨粉的研究

在1143～1213 K、120～1500 s参数范围内以Ag-Cu-Ti箔为钎料对TiAl合金与42CrMo钢进行了真空钎焊试验.采用光学显微镜、扫描电镜、元素面扫描和能谱分析等方法对界面组织进行了分析,测量了界面反应层厚度.分析了界面反应层的形成过程及受控因素,计算了反应层成长的动力学参数.结果表明,接头界面反应层包括靠近TiAl合金的AlCuTi+Ti3Al层、AlCu2Ti层以及靠近42CrMo钢的TiC层,其成长活化能分别为324.97、207.97、338.03 kJ/mol.TiAl合金与钎科的界面反应层受控于液态钎料中的Cu元素,成长较快:42CrMo钢与钎料间的TiC层受控于固态钢中C元素,成长较慢.脆性反应层AlCuTi+Ti3Al层厚度为3.3μm时接头强度最高,脆性层厚度继续增大,接头强度显著下降.     

复合阻隔法的阻隔效应原理及其在扩散连接中的应用

以TiAl金属间化合物增压涡轮与 4 0Cr钢轴的扩散连接为背景 ,提出了复合阻隔法扩散连接工艺 ,并探讨了阻隔效应原理 ,建立了从材料的扩散连接性角度出发的原子半径、原子电负性阻隔层选择原则。利用本文的扩散连接阻隔效应原理 ,确定了TiAl金属间化合物增压涡轮与 4 0Cr钢轴的扩散连接复合阻隔层为Ti/V/Cu ,由此得到的扩散连接接头在V/Cu及Cu/ 4 0Cr的连接界面处出现了对连接性能有利的无限固溶体层 ,在TiAl/Ti的接触面上生成了能够强化接头强度的Ti3 Al TiAl双相层和Ti的固溶体层 ,与TiAl/ 4 0Cr直接扩散连接相比 ,Ti/V/Cu复合阻隔层的加入 ,避免了在TiAl/4 0Cr的接触面上TiC、Ti3 Al、FeAl、FeAl2 金属间化合物脆性相的产生 ,接头强度高达4 2 0MPa ,因此利用本文的阻隔效应原理可以很好地进行复合阻隔层的选择     

Ag-Cu-Ti钎料高频感应钎焊TiAl/40Cr

采用高频感应加热的方式 ,在Ar气保护条件下 ,用Ag -Cu -Ti钎料实现了TiAl基合金与 4 0Cr钢的钎焊连接 ;采用扫描电镜、电子探针、X射线衍射分析等手段对断口、界面、生成相进行了分析 ,并且测试了接头的抗拉强度。结果表明 ,在界面上有Ti(CuAl) 2 、Ag[s,s]、TiC等反应相生成 ,典型接头界面结构为TiAl/Ti(CuAl) 2 +Ag[s ,s]/Ag[s,s]/TiC/ 4 0Cr) ;断裂位置及接头的抗拉强度随保温时间而变化 ;当钎焊连接温度为 114 3K ,保温时间 0 .9ks时接头抗拉强度值最高 ,达到 2 98MPa,断裂主要发生在Ti(CuAl) 2 层内部     

SiC／TiAl界面固相反应研究

使用扫描电子显微镜、电子能谱仪、X射线衍射仪对经950～1100℃热处理的SiC/TiAl平面界面偶界面固相反应层的成分分布、微结构及相组成等进行了分析研究,讨论了SiC/TiAl界面固相反应机制,并对热处理过程中反应层成长的动力学过程进行了探讨,获得相应的动力学方程.结果表明,SiC/TiAl界面固相反应层主要由TiC、Ti5Si3Cx及Ti(Al,Si)2构成.其中,TiC和Ti5Si3Cx主要富集于邻近SiC的反应区,而Ti(Al,Si)2富集于邻近TiAl侧的反应区.SiC/TiAl界面固相反应的发生归因于TiC和Ti5Si3Cx数值大的负吉布斯自由能变化.SiC/TiAl界面固相反应层遵循抛物线生长规律,为扩散控制的反应过程,反应速率常数为:K=8.47×10-3exp(-322×103/RT)(m2/s).     

TiAl/40Cr高频感应钎焊接头的界面组织及力学性能

以Ag-Cu-Ni-Li为钎料对TiAl与40Cr进行了高频感应钎焊,研究了TiAl/40Cr钎焊接头的界面组织和力学性能.采用扫描电镜、电子探针、X射线能谱分析仪等分析了界面组织及生成相,测试了接头的抗拉强度及界面生成相的显微硬度.结果表明:钎料与2种母材发生界面生反应成Al3Ti、Ag[s,s]、Ti(CuAl) 2、Ti2Ni和TiC等多种反应相,接头界面结构Al/A为Til3Ti/Al3Ti十Ag[s,s]/Ti(CuAl)2 Ti2Ni Ag[s,s]/TiC/40Cr.在实验所选的工艺参数范围内,当连接温度θ=850℃,保温时间t=180 s时,接头的抗拉强度达到265 MPa.     

TiAl/Ti/V/Cu/40Cr钢扩散连接界面组织结构对接头强度的影响

研究了TiAl/Ti/V/Cu/40Cr钢的扩散连接，结果显示：在TiAl/Ti界面处形成了对接头强度有利的Ti3Al TiAl双相层及Ti固溶体层，而Ti/V/Cu/40Cr界面处未出现金属间化合物及其它脆性相，接头最高拉伸强度可达420MPa，接近TiAl母材。     

保温时间对TiAl合金与镍基合金扩散连接界面组织结构及连接强度的影响

采用纯钛箔做中间层扩散连接TiAl合金与镍基高温合金(GH99).利用扫描电镜、电子探针和X射线衍射等手段对界面产物及接头的界面结构进行分析.结果表明,GH99/Ti界面主要由四个反应层组成,分别为(Ni,Cr)ss,富Ti-(Ni,Cr)ss,TiNi和Ti2Ni.当保温时间较短时,Ti/TiAl界面反应层主要为Ti(Al)ss.延长保温时间,此界面反应层转化为Ti3Al和Al3NiTi2.随着保温时间的延长,TiNi反应层厚度持续增加,而Ti2Ni反应层厚度先增加后减小.随保温时间的延长接头的抗剪强度先增加后减小,然后又增加.由接头断口形貌可以看出,接头主要断裂于Ti2Ni反应层.     

TiAl合金与镍基高温合金的扩散连接

采用钛为中间层,对TiAl合金与镍基高温合金（GH99）进了扩散连接.研究了扩散连接接头的界面结构和连接温度对界面结构及连接性能的影响,并对连接界面反应层的形成机制进行探讨.结果表明,GH99/Ti/TiAl的界面结构为：GH99/（Ni,Cr）ss/富Ti-（Ni,Cr）ss/TiNi/Ti2Ni/α-Ti＋Ti2Ni/Ti（Al）ss/TiAl＋Ti3Al/TiAl;随着连接温度的升高,各反应层厚度增加,接头的抗剪强度先增加后减小;在连接温度1 173 K,连接时间30 min,连接压力20 MPa时,抗剪强度最高为260.7 MPa.     

Si3N4/AgCu/TiAl钎焊接头界面结构及性能

采用AgCu非活性钎料实现了Si3N4陶瓷与TiAl基合金的钎焊,确定接头的典型界面组织结构为:TiAl/Ti3Al+Ti(s,s)/AlCuTi/Ag(s,s)+AlCu2Ti/Ti5Si3+TiN/Si3N4陶瓷。钎焊过程中,活性元素Ti从TiAl母材溶解到钎料中与Si3N4陶瓷发生反应润湿,实现了TiAl与Si3N4陶瓷的连接。随着钎焊温度的升高及保温时间的延长,靠近Si3N4陶瓷的TiN反应层厚度增加,Ag基固溶体中弥散分布的AlCu2Ti化合物聚集长大成块状,导致接头性能下降。当钎焊温度T=860℃,保温时间为5min时接头抗剪强度达到最大值124.6MPa。基于反应热力学及动力学计算TiN层反应激活能Q约为528.7kJ/mol,860℃时该层的成长系数KP=2.7×10-7m/s1/2。     

Ag-Cu-Ti钎料高频感应钎焊TiAI／40Cr

采用高频感应加热的方式，在Ar气保护条件下，用Ag-Cu-Ti钎料实现了TiAl基合金与40Cr钢的钎焊连接；采用扫描电镜、电子探针、X射线衍射分析等手段对断口、界面、生成相进行了分析，并且测试了接头的抗拉强度。结果表明，在界面上有Ti(CuAl)2、Ag[s，s]、TiC等反应相生成，典型接头界面结构为TiAl／Ti(CuAl)2 Ag[s，s]／Ag[s，s]／TiC／40Cr)；断裂位置及接头的抗拉强度随保温时间而变化；当钎焊连接温度为1143K，保温时间0．9ks时接头抗拉强度值最高，达到298MPa，断裂主要发生在Ti(CuAl)2层内部。     

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.     

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.     

Directional Growth of Tin Crystals Controlled by Combined Solute Concentration Gradient Field and Static Magnetic Field

A new method was introduced to achieve directional growth of Sn crystals. Microstructures in liquid(Pb)/liquid(Sn) diffusion couples were investigated under various static magnetic fields. Results show that the β-Sn crystals mainly reveal an irregular dendritic morphology without or with a relatively low static magnetic field(B0.3 T). When the magnetic field is increased to 0.5 T, the β-Sn dendrites close to the final stage of growth begin to show some directional character. With a further increase in the magnetic field to a higher level(0.8–5 T), the β-Sn dendrites have an enhanced directional growth character, but the dendrites show a certain deflection. As the magnetic field is increased to 12 T, the directional growth of the β-Sn dendrites in the center of the couple is severely destroyed. The mechanism of the directional growth of the β-Sn crystals and the deflection of the β-Sn crystals with the application of static magnetic field was tentatively discussed.     

电化学噪声数据处理方法概述

综述了常见的电化学噪声数据处理方法,介绍了直流趋势剔除、统计分析、快速傅立叶变换(FFT)法计算功率谱密度(PSD)以及小波变换处理电化学噪声信号的基本过程,并阐释了各种数学处理及所得参数的物理意义。