超高碳Cr-Si-Mn耐磨钢的组织与性能研究

研究了一种超高碳Cr-Si-Mn耐磨铸钢的热处理工艺对钢的微观组织,强韧性,以及静磨料磨损条件下磨损性能的影响。结果表明,随淬火温度的升高,微观组织由细小的隐晶性马氏体过渡到明显的粗针片状马氏体组织。钢的硬度随淬火温度的升高而降低,但冲击韧度升高。在830℃淬火,200℃回火时,钢的硬度约63HRC,冲击韧度约为4 J·cm-2。随回火温度的提高,钢的硬度逐渐下降,韧性的变化不显著。在830℃淬火,200℃回火的条件下,实验钢具有较好的静磨料磨损性能,磨损主要表现为切削机制,耐磨性主要是受硬度影响。     

热处理工艺对高强韧耐磨铸钢组织和性能的影响

研究了淬火温度及回火温度对高强韧耐磨铸钢组织和性能的影响.结果表明:淬火温度低于930 ℃时,材料的硬度随淬火温度的升高而增大;高于930 ℃时,硬度降低,在930 ℃出现硬度峰值;冲击韧度随淬火加热温度的升高先降低后增大.随着回火温度的升高,材料的硬度缓慢降低,而冲击韧度值升高.高强韧耐磨铸钢经930 ℃×2 h淬火(油淬)+240 ℃×2 h回火+240 ℃×2 h回火后,具有较高的强韧性,硬度≥54 HRC,冲击韧度≥43 J/cm~2,组织为回火马氏体+少量的残留奥氏体,试样冲击断口为准解理断裂.     

SDPM钢高硬度均匀性热处理工艺研究

利用热膨胀仪对塑料模具钢SDPM在不同冷速下的过冷奥氏体连续冷却转变行为进行了研究,并探讨了不同淬火方式获得的两种组织经不同温度回火后的组织和硬度的变化规律。结果表明:SDPM钢过冷奥氏体连续冷却过程只包括贝氏体和马氏体转变,而无珠光体或铁素体转变;当冷速在0.02~0.5℃/s时,转变产物以贝氏体和M/A岛混合组织为主;当冷速大于0.5℃/s时,转变产物以马氏体转变为主。SDPM钢的回火温度从510℃升高到570℃,马氏体淬火组织的硬度从40.3 HRC下降到37.7 HRC,等温贝氏体淬火组织硬度从39.5 HRC下降到38.2 HRC;继续升高回火温度到610℃时,马氏体淬火组织硬度下降到32.8 HRC,等温贝氏体组织硬度下降到33.6 HRC。获得最佳硬度均匀性的回火温度为550℃。     

含铝超高碳钢组织及力学性能的研究

研究了淬火温度对含铝Si-Mn-Cr系超高碳钢的组织与力学性能的影响。结果表明,Al的添加可抑制钢中网状碳化物的形成,钢的相变临界温度Ac1提高到了800℃左右。随淬火温度的提高,组织有粗化的倾向,片状马氏体形态更加明显,850℃淬火后获得细小的马氏体组织;残余奥氏体含量有所增加,最高达到6.5%;钢的硬度逐渐下降,冲击韧度变化不大,抗冲击磨料磨损性能降低。850℃淬火,200℃回火后钢的硬度可达62 HRC,冲击韧度为6 J/cm2,且抗磨料磨损性能最好。     

含铝超高碳钢组织及力学性能的研究

研究了淬火温度对含铝Si-Mn-Cr系超高碳钢的组织与力学性能的影响。结果表明,Al的添加可抑制钢中网状碳化物的形成,钢的相变临界温度Ac1提高到了800℃左右。随淬火温度的提高,组织有粗化的倾向,片状马氏体形态更加明显,850℃淬火后获得细小的马氏体组织;残余奥氏体含量有所增加,最高达到6.5%;钢的硬度逐渐下降,冲击韧度变化不大,抗冲击磨料磨损性能降低。850℃淬火,200℃回火后钢的硬度可达62 HRC,冲击韧度为6 J/cm2,且抗磨料磨损性能最好。     

多元低合金耐磨钢的强韧化处理

为了研究热处理对多元低合金耐磨钢组织及性能的影响,对其进行了不同温度下的淬火和回火处理,采用金相显微镜、扫描电镜、X-射线衍射仪、洛氏硬度计、冲击试验机等多种检测手段分别研究了其显微组织和力学性能的变化,并最终确定了低合金耐磨钢合理的热处理工艺。结果表明,淬火和回火温度对试验钢的组织及性能有着不同程度的影响。试验钢的最佳热处理工艺为910℃×1.5 h淬火+230℃×2 h回火,经此工艺处理后,试验钢的晶粒细小,组织为回火马氏体、残留奥氏体和少量碳化物,其硬度达到50 HRC,冲击韧度值大于42 J·cm-2,韧性得到了明显改善,具有良好的综合力学性能。     

热处理对中碳Cr2MnSiV耐磨铸钢组织性能的影响

研究了淬火和同火温度对中碳Cr2MnSiV耐磨铸钢的组织和力学性能的影响.结果表明:实验钢的硬度随淬火温度的升高基本保持不变,硬度值为54～53 HRC,冲击韧度随淬火温度的升高显著提高,1050℃淬火、250℃回火后达到60 J/cm2.回火温度超过250℃,硬度和冲击韧度均下降.     

热处理对机床用高速钢刀具组织和力学性能的影响

使用不同工艺对机床用W18Cr4V高速钢刀具进行了热处理,研究了热处理工艺参数对钢组织和性能的影响。结果表明,试验钢球化退火组织为球状珠光体+细小粒状碳化物,淬火组织为马氏体+残余奥氏体+少量碳化物,回火组织为回火马氏体+少量粒状碳化物及残余奥氏体。随着淬火温度的提高,抗拉强度、硬度和冲击韧度均先升高后降低,1200℃时达到最大值。随着回火温度升高,硬度先降低后升高,400℃时最低,600℃最高为65 HRC。综合考虑硬度及强韧性等因素,最优淬火温度为1200℃,最优回火温度为600℃。     

60Si2CrA的淬透性及低温回火温度对组织性能的影响

利用DIL805A热膨胀仪并结合显微组织-硬度法,测得60Si2Cr A钢的临界冷却速度;并且对该钢淬火+低温回火后的回火马氏体组织、硬度及冲击韧度作了分析研究。结果表明:60Si2Cr A钢的临界冷却速度为3~5℃/s,低于该冷却速度主要发生珠光体转变;该钢870℃淬火后低温回火,回火温度越高,硬度越低,冲击韧度越高;该钢200℃低温回火4 h,可得到最佳的综合性能。     

3种模具钢组织与性能的对比研究

采用金相显微镜、洛氏硬度计、冲击试验机与扫描电镜(SEM)对淬火+回火热处理后的SKD11钢、GD钢和LD钢的组织、硬度、冲击韧性及断口形貌进行了测试和分析。研究结果表明:3种钢经淬火+回火后的组织均由针状马氏体+碳化物+少量残余奥氏体构成,但马氏体和碳化物的形态有明显不同;淬火+回火后SKD11钢的硬度值为55.6 HRC,冲击能量约为63 J,GD钢的硬度值为58.6 HRC,冲击能量约为31 J,LD钢的硬度值为58.8 HRC,冲击能量约为75 J。3种模具钢断口宏观形貌均呈现出微量塑性变形的微晶瓷状特征,微观断口形貌为撕裂棱相连的小块解理面,3种钢的断裂机理均为准解理脆性破断。     

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。