Ti3Al5Mo5V合金在热压缩变形状态下的组织和应力分析

采用Gleeble-1500热模拟机对Ti3Al5Mo5V合金进行热压缩变形，对α β相、β相钛合金变形后的显微组织进行了分析，比较了合金在不同变形条件下所产生的应力变化趋势和影响因素。结果表明，在Ti3Al5Mo5V合金热变形中，α β相无论在高应变速率还是在低应变速率下，都发生了再结晶，且随温度升高所产生的应力急剧下降，流变软化明显，应力对温度变化敏感。β相在高应变速率下产生动态回复，低应变速率下只发生晶界滑移，应力对温度变化不敏感。     

Al-Mg-Li合金的动态软化行为及组织演变

采用Gleeble-3500热压缩模拟试验机对Al-5Mg-2Li-0.1Zr-0.1Sc铝锂合金在变形温度为623～753 K及应变速率为0.01～10 s^-1的热变形条件下进行热压缩试验,利用光学显微镜和电子背散射衍射研究了合金在不同变形条件下的组织演化,构建了合金的热加工图。建立了基于双曲正弦函数的合金热变形特征本构方程。结果表明：合金的变形激活能Q为136.159 kJ/mol,合金的流变应力随着变形温度的升高和应变速率的降低而减小;随着应变速率的增大,流变应力达到峰值应力后,动态软化和加工硬化的影响相互交替,流变应力曲线呈周期性波动。随着变形温度的升高和应变速率的降低,小角度晶界合并为大角度晶界,位错密度逐渐降低,析出相数量减少,变形织构减少,再结晶晶粒长大,动态软化机制转变为动态再结晶。     

2026铝合金热压缩变形流变行为研究

在Gleeble-1500热模机上对2026铝合金进行了热压缩实验,研究该合金在变形温度为300～500℃、应变速率为0.01～10 S-1条件下热压缩变形流变应力行为.结果表明:流变应力开始随应变的增加而增大,出现峰值后逐渐减小并趋于平稳,表现出流变软化特征;应力峰值随温度的升高而减小,随应变速率的增大而增大;可用包含Zener-Hollomon参数的Arrhenius双曲正弦关系来描述2026铝合金热变形行为,其变形激活能为256.02KJ/mol.合金热压缩变形的主要软化机制由动态回复转化为连续动态再结晶.     

挤压Mg-Li-Zn-Ce-Y-Zr合金的热变形行为

在温度T=250~450℃,应变速率为0.001~10s-1的条件下,利用Gleeble-3500热模拟试验机对挤压Mg-7.8%Li-4.6%Zn-0.96%Ce-0.85%Y-0.30Zr合金进行高温热压缩试验,分析流变应力曲线特点。合金的流变应力曲线表现出动态再结晶特征,动态再结晶是热变形过程中的主要软化机制。流变应力峰值随温度的降低和应变速率的增大而升高。稀土相化合物和α相促进β相的动态再结晶,使α相再结晶减缓。在热变形过程中动态再结晶迅速,流变应力曲线表现为临界应变较小,加工硬化迅速被动态软化所掩盖。     

半固态7050铝合金热压缩变形行为

在Gleeble-3500热模拟机上对半固态7050铝合金进行了高温热压缩试验,研究了该合金在变形温度为420～465℃、应变速率为0.001～0.100s-1条件下的流变应力行为以及变形过程中的显微组织。结果表明,流变应力在变形初期随着应变的增大迅速增大,出现峰值应力后逐渐平稳,流变应力随着应变速率的增大而增大,随着变形温度的升高而下降;流变应力可以用双曲线正弦形式的关系来描述,通过线性拟合计算出该材料的形变激活能等参数,获得流变应力的本构方程。随着变形温度升高和应变速率降低,合金中拉长的晶粒变大,合金热压缩变形的主要软化机制为动态再结晶。     

Delta工艺Inconel 718合金热变形条件下的流变行为

在Gleeble-3500热模拟实验机上对Delta工艺Inconel 718合金进行高温压缩实验,研究其高温压缩变形的流变应力行为。结果表明:δ相时效态Inconel 718合金在本实验条件下具有正的应变速率敏感性,流变应力随着应变速率的降低和变形温度的升高而减小,动态再结晶是合金重要的软化机制。δ相时效态Inconel 718合金的热变形激活能为497.407 kJ/mol,高温压缩峰值流变应力与变形温度和应变速率的关系可用双曲正弦函数表示。     

Ti-5Al-5Mo-5V-1Cr-1Fe合金的高温塑性变形行为

在Gleeble-1500热模拟机上对Ti-5Al-5Mo-5V-1Cr-1Fe合金进行高温热压缩实验,研究该合金在变形温度为750~900℃、应变速率为0.001~1 s 1条件下的流变应力行为。利用光学显微镜分析合金在不同变形条件下的组织演化规律。结果表明:合金的流变应力随着应变速率的增大和变形温度的降低而增大;流变应力随着应变的增加而增大,出现峰值后逐渐趋于平稳;变形过程中的流变应力可用Arrhenius双曲正弦本构关系来描述,平均变形激活能为454.2 kJ/mol;各种变形条件均可细化原始晶粒尺寸。随着温度的升高和应变速率的降低,合金的主要软化机制由动态回复逐渐变为动态再结晶;在(α+β)相区变形(750~850℃)时,α相对β晶粒的动态再结晶的发生起到阻碍作用。     

7150铝合金高温热压缩变形流变应力行为

在Gleeble-1500热模拟机上对7150铝合金进行高温热压缩实验,研究该合金在变形温度为300~450 ℃和应变速率为0.01～10 s~(-1) 条件下的流变应力行为.结果表明:流变应力在变形初期随着应变的增加而增大,出现峰值后逐渐趋于平稳;峰值应力随着温度的升高而减小,随着应变速率的增大而增大;可用包含Zener-Hollomon参数的Arrhenius双曲正弦关系来描述合金的热流变行为,其变形激活能为226.698 8 kJ/mol;随着温度的升高和应变速率的降低,合金中拉长的晶粒发生粗化,亚晶尺寸增大,再结晶晶粒在晶界交叉处出现并且晶粒数量逐渐增加;合金热压缩变形的主要软化机制由动态回复逐步转变为动态再结晶.     

Pd-20W合金的热压缩变形行为和显微组织

采用Gleeble-3500热模拟试验机对Pd-20W合金进行热压缩试验,研究了合金在变形温度1000~1200 ℃、应变速率0.001~1.000 s^-1条件下的流变应力以及变形过程中的显微组织。结果表明,合金的流变应力在变形初期随着真应变的增大快速上升,出现峰值应力后逐渐下降并达到稳态或略有下降。该合金热压缩变形的流变应力行为可用Zener-hollomon参数来描述,拟合计算得到了该材料的形变激活能等参数,获得流变应力的本构方程。热压缩变形后合金组织呈现一定程度的协同变形特征,晶界动态再结晶趋势增强,合金的主要软化机制为动态再结晶,表现出典型的应变诱发晶界形核机制特点。     

热变形条件对2124铝合金流变应力和显微组织的影响

采用Gleeble热模拟试验机对2124铝合金进行热压缩试验,通过分析合金在高温塑性变形过程中的流变应力变化规律,以及利用光学显微镜和透射电镜观察合金在热变形过程中的显微组织演变,探讨了不同变形温度和应变速率对合金热塑性变形能力的影响。结果表明,2124铝合金在热变形中的流变应力稳态值随热变形温度的升高或应变速率的减小而增大,可用双曲正弦形式的本构方程来描述热变形条件和流变应力的关系,合金的变形激活能为170.13 k J/mol。在较低变形温度或较高应变速率下,热变形后合金组织中存在大量位错缠结和位错墙,软化机制主要为动态回复。随变形温度的升高或者应变速率的降低,该合金组织中出现了再结晶晶粒,软化机制逐渐向动态再结晶转变。     

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。