汽轮机材料1Cr12Ni2W1Mo1V超临界钢的热压缩流变应力行为

为研究不同工艺参数对汽轮机材料1Cr12Ni2W1Mo1V超临界钢高温变形行为的影响,在变形温度1000~1150℃,应变速率0.005~5 s~(-1)的条件下进行热压缩试验,得到了相应的真应力-真应变曲线。结果表明:1Cr12Ni2W1Mo1V超临界钢的高温流变应力对温度和应变速率比较敏感。通过双曲正弦本构方程和线性回归分析构建1Cr12Ni2W1Mo1V高温塑性变形的本构模型,并将流变应力的预测值与实验值进行比较,二者拟合程度高,表明该模型能较好描述该钢在热变形过程中的流动行为。     

45Cr4NiMoV钢动态再结晶模型研究

采用Gleeble热模拟试验机对45Cr4Ni Mo V钢在变形温度1000~1150℃,应变速率0.002~5s-1,最大变形量为55%的条件下进行热模拟压缩试验。采用Poliak EI和Jonas J J等人对θ-σ(θ=dσ/dε为加工硬化率)曲线的描述,建立了45Cr4Ni Mo V钢在变形参数范围内的动态回复曲线(DRV)。通过对变形过程中的动态再结晶体积分数XD与应力参数之间的关系拟合,得到了45Cr4Ni Mo V钢在变形参数范围内的动态再结晶体积分数模型为:XD=1-exp-1.29ε-εcε0.5εε2.304εε。     

2.25Cr-1Mo-0.25V钢高温流变应力的BP神经网络模型

以2.25Cr-1Mo-0.25V钢热压缩实验得到的数据为样本,采用BP神经网络的方法建立了以应变、应变速率、变形温度为输入和流变应力为输出的流变应力模型,并采用遗传算法优化了网络的初始权值和阈值。结果表明,利用BP神经网络建立的2.25Cr-1Mo-0.25V钢热变形人工神经网络模型的可行性较高,拟合程度是0.52%。该模型较精确地预测了2.25Cr-1Mo-0.25V钢的高温流变行为,为更加合理地制定热工艺参数提供了依据。     

45Cr4NiMoV合金动态再结晶临界应变

采用Gleeble热模拟试验机对45Cr4Ni Mo V合金在变形温度为1000~1150℃,应变速率为0.002~5 s-1,最大变形量为55%的条件下进行热模拟压缩试验。通过对采集到的数据进行处理,结合lnθ-ε曲线的拐点及-(lnθ)/ε-ε曲线的极小值判据,建立了45Cr4Ni Mo V动态再结晶临界应变模型。结果表明,45Cr4Ni Mo V合金动态再结晶临界应变随变形温度递增以及应变速率递减而增加,临界应变εc与峰值应变εp之间满足:εc=0.42761εp,动态再结晶临界应变模型为:εc=0.000522Z0.15142。     

铸态30Cr2Ni4MoV钢动态再结晶行为研究

利用Gleeble-1500D热模拟机模拟高温镦粗,研究铸态30Cr2Ni4Mo V钢在1 000~1 250℃、应变速率为0.001 s-1~0.1 s-1变形条件下的热变形行为。通过对实验数据分析,得到了该钢的流动应力曲线,高温塑性本构方程,热变形激活能,建立了铸态30Cr2Ni4Mo V钢动态再结晶动力学模型和动态再结晶晶粒尺寸模型,为优化低压转子钢大锻件在高温条件下锻造加工工艺提供理论依据。     

2.25Cr1Mo0.25V大钢锭热变形混晶组织的演变

参照实际热变形工艺,对2.25Cr1Mo0.25V钢锭进行了高温均匀化处理与热镦粗试验。研究了热变形条件对高温力学行为、粗晶组织的影响,得出了最佳的热力学参数。并且,着重对实际工艺中的混晶现象进行了判断分析并提出了预防措施。研究结果表明,对于2.25Cr1Mo0.25V加氢反应器用钢锭,热变形条件最佳参数为变形量20%、变形温度1150℃、应变速率0.1s-1。此时混晶比值D max/D0为3.1,最小几何晶粒尺寸D0为27～36μm,最大晶粒尺寸D max为99～136μm。随变形温度的升高、变形时间的延长,混晶结构逐渐消失。     

2.25Cr-1Mo-0.25V钢的热变形行为及其形变组织

采用Gleeble3500热模拟试验机对加氢反应器用2.25Cr-1Mo-0.25V钢进行不同变形温度、不同应变速率的热压缩变形试验,并分析和讨论了再结晶组织的演变规律。结果表明,该钢高温流变应力和峰值应变随变形温度的降低和应变速率的提高而增大,确定了热变形激活能和热变形方程;再结晶晶粒的数量随应变量的增加而增加;变形温度越高,应变速率越小,再结晶现象更容易发生,并且进行的更完全。     

热循环峰值温度对2.25Cr1Mo0.25V钢组织和性能的影响

采用Gleeble-1500热模拟试验机在不同的峰值温度条件下对2.25Cr1Mo0.25V钢焊接热影响区组织与性能进行模拟研究。通过金相及断口分析,研究与讨论了热循环峰值温度对2.25Cr1Mo0.25V钢组织与性能的影响。试验结果表明,峰值温度为1200℃时组织粗大、韧性差。峰值温度为1000℃时晶粒细小、组织分布均匀且韧性最好。峰值温度分别为750与620℃时的组织与未循环材料相近,韧性较好。     

35CrMo钢热变形机制的模拟研究

以弯曲镦锻 3 5 Cr Mo钢火车曲轴为例 ,通过将该钢以 90 0℃～ 1 2 5 0℃变形温度 ;0 .0 5 s-1、0 .5s-1、1 .0 s-1的应变速率 ;在 Greeble-1 5 0 0试验机上进行压缩 1 5 %～ 80 %的热变形实验 ,和随后进行的微观组织分析得出了 :材料热变形屈服应力变化模型 ;材料热变形本构关系 ;动态与静态再结晶模型和热加工参数与微观组织变化的相关性资料。描绘了在 1 2 5 0℃ ,应变速率为 1 .0 s-1时 ,3 5 Cr Mo钢热变形应力应变曲线和相应的再结晶组织。通过对 3 5 Cr Mo钢在高温大变形条件下 ,试件内部各区域晶粒尺寸的回归计算 ,验证了该钢热变形晶粒计算模型。所得出的实验结果和计算模型为热成形工艺分析和质量控制提供了科学的依据     

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 基于焊接物理模拟技术,在Gleeble3500热模拟试验机上,采用不同t8/5,对3Cr 1Mo 0.25V钢焊接热影响区粗晶区的热循环过程进行了模拟。同时,利用热膨胀法测定了模拟焊接热影响区的奥氏体连续冷却转变曲线。观察了模拟粗晶区的光学显微组织,测定了相应的维氏硬度,分析了合金元素对3Cr 1Mo 0.25V钢焊接粗晶区奥氏体连续冷却转变组织及其性能的影响。试验结果为3Cr 1Mo 0.25V钢焊接工艺的选取和制定提供了参考。     

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。