不同冷速下36Mn2V钢坯高温塑性及碳氮化物的析出

采用Gleeble-1500热模拟试验机研究了微合金钢36Mn2V连铸坯试样在冷速为3、8和15℃/s,变形温度为650～1000℃/s之间的高温塑性,并通过试样的断口形貌、显微组织和微合金析出相等的变化情况分析其脆化机理。结果表明：实验钢的第Ⅲ脆性温度区为950～650℃/s,800℃以上脆化是由碳氮化物单一原因造成,800℃以下脆化的原因则是碳氮化物的析出和沿晶界铁素体膜的形成;冷速过快加剧900～700℃温度区间的脆化;900℃已有大量碳氮化物的析出,随变形温度的降低,析出量减少,750℃仍然存在碳氮化物的析出。     

22MnB5热成形钢连铸坯高温力学性能研究

采用Gleeble-3800热模拟试验机对22MnB5热成形钢连铸坯在600～1300℃温度范围内的高温力学性能进行了测试，借助扫描电镜观察了高温拉伸后的断口形貌。系统分析了形变温度对应力-应变曲线、高温强度及热塑性的影响。结果表明，22MnB5热成形钢连铸坯的高温拉伸过程是形变强化和动态软化共同作用的结果，高温强度随形变温度的升高而下降。22MnB5热成形钢连铸坯的第1脆性区在1250℃至熔点范围内，为S和P元素在枝晶间偏析导致晶界熔融所致。第3脆性区在650～750℃范围内，为奥氏体晶界BN析出和奥氏体→铁素体相变所致，加入Ti可使第3脆性区变窄且趋向较低温度区。在800～1200℃温度范围内22MnB5热成形钢连铸坯塑性良好，可为此类钢的连铸工艺制定提供参考，以减少铸坯裂纹缺陷的产生。     

邯钢高强船板A36高温力学性能试验研究

采用Gleeble-1500对高强船板A36钢种进行了热模拟研究,通过分析在不同温度下的高温力学性能和断口形貌,得知高强船板A36钢种在600℃至熔点范围内,存在两个脆性温度区,即1330℃至熔点的第Ⅰ脆性温度区和600～1000℃的第Ⅲ脆性温度区。A36钢种在第Ⅲ脆性温度区的脆化原因是由钢中AlN、NbCN等质点的析出引起奥氏体单相区的脆化导致。     

37Mn5连铸坯高温热塑性的研究

在Gleeble-1500D热模拟机上,针对37Mn5钢连铸坯,进行了热塑性测试.分析了37Mn5试样的显微组织及试样断口性质与塑性的关系.研究了第Ⅲ脆性区的脆化原因.实验结果表明:在1 300℃至800℃区间存在两个脆性温度区,第Ⅲ脆性温度域为900～800 ℃,其断面收缩率ψ=60.23%～29.61%;为指导37Mn5管坯钢的生产实践提供理论依据.     

2205双相不锈钢连铸坯的高温力学性能研究

利用Gleeble-1500热模拟试验机对2205双相不锈钢连铸坯进行高温拉伸试验;分析了抗拉强度和断面收缩率随温度的变化情况;利用扫描电镜观察了试样的断口形貌。结果表明,测得该试样在750～1421℃存在3个脆性温度区;双相不锈钢连铸坯在第Ⅲ脆性温度区脆化主要是因为在晶界上的存在TiN类细小析出物,而第Ⅱ脆性区的脆化主要是由于枝晶间存在显微疏松和偏析。     

高铁刹车盘用CrMoV钢的高温热塑性

采用Gleeble-3800热模拟试验机研究了600～1350℃范围内高铁刹车盘用CrMoV钢的高温热塑性,利用扫描电镜观察断口形貌,利用光学显微镜观察断口截面显微组织.结果表明:试验钢在600～1350℃范围内存在3个脆性温度区间,即熔点～1320℃的第Ⅰ脆性区、1100～1000℃区间的第Ⅱ脆性区和800～650℃...     

Cu-P合金化超低碳贝氏体钢的热塑性

为考察新型超低碳贝氏体钢连铸坯的热塑性,利用热模拟实验技术研究了Cu-P合金化超低碳贝氏体钢在750～1350℃温度范围的拉伸应力-应变行为,热塑性和拉伸断口的变化,分析了产生这些变化的原因和磷对热塑性的影响机理。结果表明：Cu-P合金化使超低碳贝氏体钢高温拉伸时发生颈缩的应变量减小,但在750～1300℃温区的断面收缩率均达到60%以上。钢中微量硼有效抑制磷在奥氏体晶界的偏聚以及降低先共析铁素体的相变温度是高磷钢保持良好热塑性的主要原因。在800～900℃热塑性的下降与形变诱发Nb（C,N）粒子析出有关。根据热塑性和抗拉强度的变化规律,建议连铸坯在一冷区采取强冷,使表面温度迅速降低到1350℃以下,在二冷区采取弱冷,温度保持在800℃以上,从而使连铸坯始终具有较高的热塑性。     

27SiMn钢连铸坯热塑性研究

应用Gleeble3800热模拟试验机,对27SiMn钢连铸坯进行了热塑性测试。分析了27SiMn试样的显微组织与脆性的关系,研究了测试温度范围内钢的脆化原因。试验结果表明:550~1200℃的脆性温度区域为600~850℃,其断面收缩率z=23.0%~50.0%;塑性温度区域为900~1200℃,其断面收缩率均在60%以上,为指导27SiMn钢的连铸生产提供理论依据。     

高碳钢72A热成形性能

用Gleebe-1500热模拟试验机对国内钢厂生产的72A热轧盘条的热塑性进行研究,利用扫描电镜及光学显微镜分析高温脆化原因。结果表明,72A钢的第Ⅲ脆性温度区为700～850 ℃,断面收缩率均低于60%。72A钢在850~823 ℃时的脆化机理为晶界处细小第二相粒子TiN的析出;在823 ℃以下时的脆化机理是晶界处铁素体薄膜的析出。     

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 应用Gleeble3800热模拟试验机，针对27SiMn钢连铸坯，进行了热塑性测试。分析了27SiMn试样的显微组织与塑性的关系。研究了测试温度范围内钢的脆化原因。试验结果表明：550~1200℃的脆性温度区域为600~850℃，其断面收缩率ψ=23.0%~50.0%，为指导27SiMn钢的连铸生产提供理论依据。     

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。