稀土—硼对熔敷金属冲击韧性的影响

本文探讨了σ_b≥850MPa的Cr-Mo-Mn-Si系熔敷金属中加稀土(Re)硼(B)和微量硼对冲击韧性的影响。研究表明,加入适量的Re要比单独加B更为理想,尤其是对低温冲击韧性而言。这主要是Re能改变夹杂物的形态以及自身形成高熔点的细小夹杂物,分布在晶界与B联合强化的缘故。     

硼含量对Mn13Cr2高锰钢铸态组织和性能的影响

借助光学显微镜、扫描电镜、X射线衍射仪、电子探针等仪器设备综合研究了硼含量(0.50～2.0%)对Mn13Cr2高锰钢铸态组织和性能的影响.试验结果表明:硼元素主要分布在硼碳化物中,并且随着硼含量的增加,合金的基体组织由奥氏体为主变为以铁素体为主,第二相由M3(C,B)为主变为M23(C,B)6和M3(C,B)为主,第二相呈网状分布特征.同时,第二相的体积分数、合金的硬度随硼含量的增加而增加,合金的冲击韧性随硼含量的增加而降低.     

稀土对硼锆共渗过程的活化催渗及其组织和性能的影响

在粉未硼锆渗剂中加入稀土元素,可使渗速提高26%。共渗层主要由(FeZr)_2B相组成,同时还渗入了微量的La、Ce、Pr元素。与渗硼、硼稀土共渗、硼锆共渗相比,硼锆稀土共渗层的耐磨性和耐蚀性好,尤其是韧性有明显提高,其脆断前吸收的功同渗硼相比提高了70%。     

少量铈对高硼高速钢微观组织与力学性能的影响

借助光学显微镜、扫描电镜和X射线衍射仪研究少量铈对高硼高速钢微观组织和力学性能的影响。结果表明:少量铈的添加能显著提高高硼高速钢的冲击韧性和磨损性能,其冲击韧性值(ak)由6.7 J/cm2增加到14.3 J/cm2,少量铈的存在使高硼高速钢中鱼骨状硼碳化物基本消失,大部分羽毛状硼碳化物熔断,粒状硼碳化物增多,硼碳化物分布更加均匀,初生奥氏体晶粒明显细化。     

硼含量对高硼中碳合金钢铸态组织与力学性能的影响

针对高性能轧辊对材质的需求,设计了一种1.0％＜ω(B)＜3.0％和ωω(c)约为0.45％的高硼中碳合金钢,并研究了硼含量对其铸态组织与力学性能的影响.结果表明:高硼中碳合金钢铸态组织由马氏体、少量残留奥氏体及共晶硼碳化合物或硼化物组成.随着B含量的增加,其组织由亚共晶形态向过共晶形态转变,共晶硬质相体积分数呈指数关系变化,材料硬度不断升高,冲击韧性下降.     

微量硼改性对钛合金组织和性能的影响

硼(B)元素改性的钛合金由于生成TiB金属间化合物而具有更高的强度、刚度和耐磨性等。目前,TiB已用作钛合金的增强相,硼改性钛合金具有扩大钛合金使用范围的潜力,并已引起了人们广泛关注。综述了微量硼改性对钛合金铸态组织和性能的影响,以及微量硼元素改性与热加工叠加或热处理对钛合金组织和性能的影响。     

余热淬火贝氏体/马氏体复合铸铁磨球的研制

研究了一种复合铸铁磨球的组织和性能。结果表明，化学成分和淬火工艺对这种复合铸铁磨球的组织和性能有很大影响。微量的硼和适量的铜可以明显地提高磨球的淬透性，经过余热淬火得到了贝氏体或马氏体基体组织，从而提高磨球的硬度和冲击韧性。     

硼含量对H型钢低温冲击韧性的影响

针对铌硼微合金化H型钢低温冲击韧性波动较大的问题,通过数据统计,分析了硼含量对H型钢低温冲击韧性的影响;采用光学显微镜、扫描电镜及透射电镜观测,对冲击值低的含硼热轧H型钢组织进行了分析,结果表明：随着硼含量增加,粒状贝氏体含量增加且在局部富集,同时在铁素体晶界上析出薄片状碳化物,导致低温冲击韧性低且波动大。为此,严格控制冶炼工艺,提高了产品实物低温冲击韧性及稳定性。     

微量硼元素添加对Ti6Al4V-xB组织及性能的影响

采用高真空非自耗熔炼及吸铸方法制备不同硼含量的Ti6Al4V-xB(x=0,0.05,0.1,0.5,质量分数,%)合金,将合金在900℃下进行2 h保温退火。研究了不同微量硼元素添加对Ti6Al4V-xB的铸造显微组织及力学性能的影响。结果表明,微量硼元素的添加影响了钛合金高温形核过程,在固-液前沿富集B元素阻碍初始β-Ti长大,有效细化钛合金晶粒,当硼含量超过0.1%时,则有TiB相的析出。Ti6Al4V-xB合金的强度极限随硼含量的增加单调上升,由893 MPa变为966 MPa,这是细晶强化和析出强化共同作用的结果;合金的塑性则是先升高后降低,Ti6Al4V-0.05B的塑性提高了15%,而Ti6Al4V-0.1B与Ti6Al4V-0.5B的塑性则降低了50%,是因为析出脆性的Ti B相,形成脆性断裂敏感带。     

离心铸造高硼高速钢辊环组织及性能研究

针对高速钢轧辊生产成本高的问题,设计一种用廉价硼元素部分取代昂贵合金元素的新型耐磨材料,离心铸造出辊环.借助扫描电镜(SEM)和X射线衍射(XRD)等手段对高硼高速钢辊环组织进行了研究,为高硼高速钢复合轧辊生产奠定基础.结果表明:铸态高硼高速钢辊环组织由马氏体、少量残余奥氏体及硼碳化物组成,硼碳化物由M2(B,C),(W,Mo)2(B,C),M3(B,C)以及M23(B,C)6组成,呈鱼骨状、筛网状和块状沿晶界分布;快速冷却下,辊环径向上合金元素无偏析.经1 050℃水淬后,共晶硼碳化物形貌和分布没有变化,部分二次硼碳化物溶解,局部有断网现象,基体中出现细小、弥散的二次析出物,经525℃回火后数量明显增加.热处理后,硬度达到HRC60.8,冲击韧性可达到8.4 J/cm2.     

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。