晶粒度等级对高铁车轮钢滚动摩擦磨损性能的影响

采用GPM-30型轮轨滚动接触疲劳试验机对比研究了3种不同晶粒度等级的ER8高铁车轮钢试样的滚动摩擦磨损性能,通过测量摩擦因数、计算磨损率、观察表面磨损形貌来评价其磨损性能。结果表明,试样晶粒度等级越高,稳态平均摩擦因数越小,磨损率越低。晶粒度11.0级试样的稳态平均摩擦因数为0.19,磨损率为0.663×10^-5 g/m,而晶粒度10.0级、晶粒度9.5级试样的稳定平均摩擦因数分别为0.26、0.35,磨损率分别为1.326×10^-5、4.421×10^-5 g/m。晶粒度9.5级试样表面的剥落损伤严重,磨损率最高。晶粒度11.0级试样磨损后表面氧化严重,在表面形成了一定厚度的氧化层,氧化层在磨损过程中起到减小摩擦的作用,因此,试样摩擦因数较小。     

Ti-33Al-3Cr-0.5Mo 合金全层片组织晶粒尺寸对其高温抗氧化性能的影响

对全层片组织３种尺寸的试样进行了９００℃，７２ｈ的高温循环氧化增重试验，研究了晶粒尺寸对Ｔｉ－３３Ａｌ－Ｃｒ－０．５Ｍｏ合金高温抗氧化性能的影响。结果表明：晶粒尺寸居中的试样具有良好的高温抗氧化性能。另外，用ＳＥＭ和ＥＤＡＸ分析了氧化层结构并探讨了氧化机理。     

Ti—33Al—3Cr—0.5Mo合金全层片组织晶粒尺寸对其高温抗氧化…

对全层片组织３种尺寸的试样进行了９００℃，７２ｈ的高温循环氧化增重试验，研究了晶粒尺寸对Ｔｉ－３３Ａｌ－３Ｃｒ－０．５Ｍｏ合金高温抗氧化性能的影响。结果表明：晶粒尺寸居中的试样具有良好的高温抗氧化性能，另外，用ＳＥＭ和ＥＤＡＸ分析了氧化层结构并探讨了氧化机理。     

H13钢经不同表面处理后的静态抗铝热熔损性能比较

将经过蒸汽氧化、离子渗氮和渗硼等不同表面处理的H13钢试样浸入铝液进行静态熔损试验，探索并建立了一套熔损评定方法一即用试样质量损失的方法评定熔损情况。对铁铝界面进行了显微观察和能谱分析。结果表明，在相同试验条件下熔损后，铁铝界面组织颜色自深至浅依次为：深色的H13钢基体、深灰色致密金属问化合物层、浅灰色致密金属问化合物层、含游离金属间化合物的铝层以及附着的铝。离子渗氮试样和渗硼试样的热熔质量损失要比氧化试样更少，显示了更好的热熔损抗力。     

喷丸对马氏体耐热钢高温蒸汽氧化行为的影响

利用高温蒸汽氧化试验装置对比研究P92、G115钢以及喷丸的G115钢的高温蒸汽氧化行为,结果表明,这3个试样的650℃蒸汽氧化动力学曲线符合ΔW=ktn规律.相同蒸汽氧化时间下G115钢的氧化质量增加远小于P92钢,主要是因为G115钢中富Cr层的形成和富Cu相在氧化层界面的析出.经喷丸处理的G115钢氧化质量增加小...     

中间热处理对0Cr18Ni10Ti不锈钢管组织及性能的改善

研究了0Cr18Ni10Ti不锈钢管制备过程中中间管坯的热处理工艺对成品管组织和性能的改善。研究表明:中间管坯经不同温度真空热处理后,管坯表面光洁,无明显氧化层且管材组织均匀,其中经1080℃×8min热处理后管坯晶粒度为6级;经900℃×60min真空热处理后管坯晶粒度为10级。中间管坯在大气环境中经1100℃×3min热处理后,管坯表面氧化严重,管坯晶粒组织粗大不均匀,在管坯内壁出现明显细晶区域。成品钢管拉伸试验表明,采用1080℃×8min真空热处理后的中间管坯所制备的成品钢管拉伸综合性能优良。     

关于用氧化法检验钢的奥氏体晶粒度的问题

采用几种不同的碳钢和合金钢,进行了氧化法和晶粒边界腐蚀法检验钢的奥氏体晶粒度的对比试验。结果表明,对于抗氧化能力较弱的碳钢,氧化法与晶粒与晶粒边界腐蚀法所显示的奥氏体晶粒度基本相符,而抗氧化能力较强的合金钢,氧化法所显示的奥氏体晶粒度较晶粒边界腐蚀法要细。含碳量大于０．３５％的碳钢,氧化法所显示的晶粒度有时往往不是钢的奥氏体晶粒度,而是奥氏体加铁体晶粒度,或铁素体晶粒度,这将给奥氏体晶粒度的检验和     

喷丸处理对Super304H钢抗蒸汽氧化性能的影响

研究了喷丸与未喷丸处理的Super304H钢在650℃/27 MPa的超临界蒸汽中的氧化行为。氧化1000和2000 h后,用金相显微镜(OM)、扫描电镜(SEM)及能谱仪(EDS)分析氧化膜表面及横截面形貌、微观结构和元素分布,用X射线衍射仪(XRD)对氧化膜物相进行表征。结果表明:喷丸处理试样的抗蒸汽氧化性能要远优于未喷丸的试样,喷丸处理可显著提高Super304H钢的抗蒸汽氧化性能并提高表面氧化膜的抗剥落性能。对Super304H钢施以喷丸处理,可使材料表面晶粒细化,引入的晶界、亚晶界和位错等缺陷,加速Cr原子在高温氧化过程中向表面扩散,促进材料表面致密富Cr氧化层(Cr_2O_3)的形成和生长。     

电流对TC4钛合金高温压缩变形显微组织的影响

为研究电场作用下升温速度对TC4钛合金高温压缩变形显微组织的影响,利用Gleeble-1500D热-力学模拟机对原始晶粒尺寸为8和20μm的TC4钛合金小圆柱体试样,分别以不同的升温速度加热至700℃进行了压缩实验。结果表明:电流作用下的高温压缩变形后,8μm的TC4钛合金晶粒更细小,等轴性较变形前好;等轴α相增多,片层β相减少;等轴α相和片层β相的分布更均匀。20μm的TC4钛合金在大电流和小电流作用下α相和β相中都出现了蜂窝状结构,且小电流作用下的蜂窝状结构比大电流作用下的蜂窝状结构明显。同等晶粒度下,电流越大,微观组织越均匀、晶粒越细小,等轴性越好。     

VM12-SHC与T92耐热钢在带压蒸汽中的抗氧化行为比较

对VM12-SHC和T92马氏体耐热钢在650℃/7 MPa及630℃/7 MPa带压蒸汽参数下进行了200、500、800、1300、2000 h抗蒸汽氧化对比试验。试样氧化增量采用电子天平测量,氧化膜厚度采用光学显微镜观察,氧化试样表面和横截面形貌采用扫描电镜(SEM)观察,微区成分和氧化物结构分别采用EDS能谱和X射线衍射(XRD)分析。试验结果表明,VM12-SHC的高温抗蒸汽氧化性能优于T92钢,650℃/2000 h和630℃/2000 h氧化速率仅分别为T92钢的65%和72%左右。随着温度升高和时间增加,VM12-SHC和T92钢在带压蒸汽中生成的氧化膜增加,氧化增量基本遵循抛物线氧化规律;氧化膜分为内外两层,外层氧化物为Fe_3O_4,内层氧化物为Fe Cr_2O_4。     

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.     

Growth Kinetics of Single Inclusion Particle in Molten Melts

On the basis of the single-particle framework, a new theory on inclusion growth in metallurgical melts is developed to study the kinetics of inclusion growth on account of reaction and collision. The studies show that the early growth of inclusion depends on reaction growth and Brawnian motion collision, and where the former is decisive, the late growth depends on turbulence collision and Stokes＇ collision, and where the former is dominant; collision growth is very quick during the smelting process, lessened in the refining process, but nearly negligible in the continuous casting process.     

Theoretical Analysis for the Motion and Temperature of Melt Droplets in Spray Degassing Process

The motion of melt droplets in spray degassing process was analyzed theoretically. The height of the treatment tank in spray degassing process could be determined by the results of theoretical calculation of motion of melt droplets. To know whether the melt droplets would solidify during spraying process, the balance temperature of melt droplets was also theoretically analyzed. Then proof experiments for theoretical results about temperature of melt droplets were carried. In comparison, the experimental results were nearly similar to the calculation results.     

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.