38CrSi钢晶粒的细化工艺

对38CrSi钢分别加热至880、900和920℃,进行3~5次的循环加热淬火,以细化38CrSi钢的晶粒。利用光学显微镜观察38CrSi钢的晶粒形貌,利用截线法测量晶粒的尺寸。结果表明:38CrSi钢晶粒细化的最佳工艺为880℃×12 min+油淬,循环3次,晶粒尺寸为5~7μm。     

循环淬火工艺对30CrMnTi组织和性能的影响

分别在840、860、880和900℃对30CrMnTi进行淬火处理,采用光学显微镜观察显微组织,并测不同淬火温度下的硬度。结果发现,经880℃淬火处理后晶粒细小且均匀,硬度达48.3 HRC。在880℃进行1~4次循环热处理,观察热处理后的显微组织,并测试硬度。结果表明,循环热处理次数增加,晶粒细化效果越明显。在880℃循环热处理3次时晶粒细化效果最佳,硬度值最大,达到58.5 HRC。     

无碳化物贝氏体/马氏体复相钢晶粒细化研究

在获得无碳化物贝氏体/马氏体复相钢奥氏体晶界侵蚀方法的基础上,利用电致加热循环淬火方法对无碳化物贝氏体/马氏体复相钢进行组织超细化处理,研究了奥氏体化温度、加热速率、循环次数和保温时间对钢的组织和原奥氏体晶粒的影响。实验结果表明:以100℃/s的加热速度加热到910~920℃淬火,循环3次,前两次淬火不保温,最后一次保温30 s,可得到平均晶粒度为3.2μm,超高周疲劳性能优异的超细化无碳化物贝氏体/马氏体复相钢。     

CrWMn循环相变超细化工艺研究

循环相变热处理过程可有效细化晶粒,进而在保证材料强度的同时提升其韧性。通过研究热处理循环次数、奥氏体化温度和保温时间探究该工艺的最佳参数。结果表明CrWMn钢在810℃淬火、保温时间10 min、循环相变4次,晶粒细化至2. 4μm,能获得较好的综合性能。其机理大致归因于该过程能大幅度提高形核率、抑制晶粒的生长及消除钢的组织遗传性。     

退火工艺对E355汽车结构钢组织和性能的影响

以工业生产的E355汽车结构用热轧钢板为试验材料开展退火试验,分析不同试验条件下E355汽车结构用热轧钢的显微组织和力学性能。结果表明:在试验条件下,随着冷却速度的升高,试样的组织细化,屈服强度、抗拉强度升高,低温冲击吸收能量降低;随着保温温度由880℃升高至920℃,奥氏体晶粒度降低,空冷和400℃炉冷试验钢的铁素体组织略微粗化,炉冷试样铁素体组织明显粗化;随着保温时间增加,试样的力学性能变化不明显,低温冲击吸收能量降低。E355钢最佳退火工艺为:880、900℃保温20 min后空冷。     

26CrMoVNbRE钢高效热处理调质工艺边界探索

研究了不同淬火温度、淬火保温时间、回火温度及回火保温时间对26CrMoVNbRE钢组织与性能的影响,结果表明,试验钢870～900℃淬火后高温回火,显微组织为回火索氏体,原始奥氏体晶粒细小均匀.870℃保温40 min淬火,与900℃保温30 min淬火屈服强度相近,前者有良好的综合力学性能,后者更有利于现场高效热处理...     

淬火工艺及Nb元素对30MnB5钢原奥氏体晶粒度的影响

利用光学显微镜(OM),研究了淬火工艺及Nb元素对30MnB5钢的原奥氏体晶粒度的影响。结果表明:含Nb的30MnB5钢在淬火温度860~920 ℃,保温时间不超过60 min时,原奥氏体晶粒度具有良好的稳定性;当淬火温度达到950 ℃时,保温时间超过30 min后,原奥氏体晶粒尺寸随着保温时间增长逐渐变大;因此,淬火温度低于950 ℃时,Nb元素对30MnB5钢热处理过程中原奥氏体晶粒生长具有抑制作用;当淬火温度达到1000 ℃时,Nb元素仅在30 min以内对原奥氏体晶粒生长有轻微抑制作用,当淬火保温时间超过60 min时,Nb元素完全失去对原奥氏体晶粒生长的抑制作用。     

18Ni马氏体时效钢循环相变细晶工艺研究

研究了循环相变对18Ni(1800 MPa级)马氏体时效钢奥氏体晶粒细化的影响.结果表明,通过加热温度递减的变温循环相变,18Ni马氏体时效钢奥氏体晶粒尺寸可由201 μm的粗大等轴晶细化为约10 μm的均匀细小晶粒;而通过950、920和900℃的等温循环相变,得到细化的晶粒尺寸为12～14μm;通过循环相变显著细化了马氏体时效钢的晶粒尺寸,而温度递减的变温循环相变是该钢细化晶粒的有效措施.     

25Mn2钢热处理工艺的优化

探讨了25Mn2钢热处理工艺的优化。实验结果表明,25Mn2钢的最佳热处理工艺为:淬火温度880~910℃,保温时间45~50 min(壁厚为10~12 mm);回火温度580~600℃,回火保温时间60 min。     

40Cr钢晶粒超细化工艺研究

对40Cr钢采用多种循环淬火工艺进行晶粒超细化处理,结果表明,其最佳超细化工艺为840℃×18min+油淬,循环4次,可使晶粒细化至13￣14级。     

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。