钢结硬质合金的马氏体等温淬火研究

研究了钢结硬质合金ＧＪＷ５０（配料成分ｗｔ％：５０ＷＣ、０．２５Ｃ、０．５０Ｃｒ、０．２５Ｍｏ、余为Ｆｅ）经１０２０℃奥氏体化、２０００℃（低于Ｍｓ点）等温淬火后的组织与机械性能．结果表明，该状态基体组织中残余奥氏体量明显多于１０２０℃淬火＋２００℃回火态，其硬度、抗弯强度与冲击韧性均高于后者，但断裂韧性略低于后者．     

W6Mo5Cr4V2钢形变等温淬火的组织和性能

对Ｗ６ＭＯ５ｃｒ４Ｖ２钢１２４０℃奥氏体化后、在１１５０℃以１．５×１０￣－２／ｓ的形变速率筹温形变０％～６５％，并在２７０℃等温淬火，５６０℃３次回火后的组织和性能进行了研究。结果表明：该钢在１０５０℃或更高温度形变会发生动态再结晶，且形变诱发析出了ＭＣ型碳化物，而使贝氏体中具有大量的碳化物颗粒；形变使等温淬火、回火组织的强度、硬度及韧度均有所提高，在１０５０℃形变１５％～２０％具有最佳的强韧性配合。     

淬火合金钢中的奥氏体稳定化

研究了马氏体(M)和贝氏体(B)两相温度区等温淬火组织中的奥氏体稳定化．在一定等温时间内，奥氏体稳定化程度，即残余奥氏体量与等温温度间的关系呈马鞍型曲线．在实验钢中，其谷底值低于用同冷却介质淬火组织中的AR，表明在一定条件下等温停留并不引起残余奥氏体量增多．可利用马鞍型曲线调整AR与M及B的含量配比，获得无变形或强韧性配合最佳的准贝氏体等温淬火工艺．奥氏体稳定化为热稳定化、化学稳定化、相致稳定化和宏观热应力稳定化诸机制的综合作用．马氏体临界点Mc点无特殊物理意义。     

高速钢形变等温淬火的力学性能及其强韧化机理

对Ｗ６Ｍｏ５Ｃｒ４Ｖ２钢奥氏体化后,在１１５０℃～７５０℃以１．５×１０－２／ｓ的形变速率等温形变０％～６５％,并对２７０℃等温淬火、５６０℃回火后组织与性能进行了研究。结果表明：形变使等温淬火、回火组织的硬度、强度和冲击韧度均有所提高,１０５０℃形变１５％～２０％具有最佳强韧性配合。并根据力学性能与组织变化的关系,提出了组织细化强韧化、位错强化、碳化物沉淀强化和锯齿状晶界韧化的强韧化机理,其中锯齿状晶界韧化对最佳强韧性配合起着关键作用。     

形变温度对中碳钢组织转变的影响

热模拟单向压缩下中碳钢形变温度低于Ad3(786℃)点时，析出形变诱导铁素体(DIF)，DIF量随形变温度降低而提高；在低于750℃形变时，DIF量远高于平衡态铁索体含量54％．DIF析出时碳原子高度富集在铁索体晶界和铁索体／奥氏体界面．在低于A1(719℃)等温处理时，高于Ad3点形变试样中，奥氏体转变为铁素体 片层状珠光体；低于Ad3点但高于Ar3(645℃)点形变时，未转变奥氏体转变为铁素体 片层状珠光体 晶界渗碳体；稍高于Ar3点形变时，将获得铁素体 弥散渗碳体的球化组织．     

热处理对非合金奥贝球墨铸铁组织和性能的影响

确定了非合金奥贝球墨铸铁（约０．８％Ｍｎ）的最佳奥氏体化的温度，并研究了等温淬火温度对其组织和性能的影响     

贝氏体型非调质钢过冷奥氏体的连续冷却转变

研究了一种 Ｍｎ Ｂ系低碳贝氏体型非调质钢过冷奥氏体的连续冷却转变,获得了试验用钢过冷奥氏体的连续冷却转变曲线。试验结果表明,本试验用钢过冷奥氏体不发生先共析铁素体析出的临界冷却速度为０．７℃／ｓ;冷却速度在１～４．５℃／ｓ 范围内可得到全部贝氏体组织;当冷速大于４．５℃／ｓ 时,不再有贝氏体生成,室温组织为马氏体和残余奥氏体。     

65Mn2SiVTi钢连续冷却转变的研究

用Ｆｏｒｍａｓｔｏｒ－Ｆ型全自动相变仪，金相显微镜和扫描电子显微镜研究了６５Ｍｎ２ＳｉＶＴｉ钢过冷奥氏体的转变动力学曲线及转变产物的组织，结果表明，６５Ｍｎ２ＳｉＶＴｉ钢不析出珠光体组织的临界冷却速度为１．３℃／ｓ，在０．１～０．５℃／ｓ冷却速度范围内可获得细片状珠光体。     

冷却速度对Fv520（B）多马氏体组织的影响

利用膨胀法、金相、ＸＲＤ法研究了冷地ＦＶ５２０（Ｂ）钢Ｍｓ点及其组织的影响。结果表明，ＦＶ５２０（Ｂ）钢具有良好的淬透性，其Ｍｓ点为１５５℃，冷和速度降低，Ｍｓ点略有升高。在冷却速度为１７．５℃／ｓ～０．０３℃／ｓ的范围内，均得到马氏体组织，冷却速度对马氏体组织状态影响不大。     

18Ni马氏体时效钢时效机理的研究

采用小角Ｘ射线散射、Ｍｏｓｓｂａｕｅｒ谱、透射电镜等方法研究了１８Ｎｉ马氏体时效钢的时效过程。结果表明，１８Ｎｉ合金在固溶处理后５００℃等温时效过程中，首先发生调幅分解，然后在调幅组织的Ｎｉ－Ｍｏ－Ｔｉ富集区以原位形核方式析出含Ｆｅ的Ｎｉ３（Ｍｏ、Ｔｉ）型金属间化合物，随时效时间延长，Ｎｉ３Ｍｏ和Ｎｉ３Ｔｉ粒子聚集长大并部分溶解，同时析出球形Ｆｅ２Ｍｏ金属间化合物，并形成逆转变奥氏体。     

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。