Cr12钢TD盐浴渗钒组织与性能研究

研究了Cr12钢制模具表面TD盐浴渗钒处理后的碳化物层的组织与性能.结果表明:Cr12钢经960℃×4.5 h TD盐浴渗钒后,形成了主要由含V和C的化合物组成的、厚约19.5μm的表面渗钒层,并且渗层厚度均匀,致密性和连续性均较好.TD盐浴渗钒经油淬和220℃×1.5 h回火后的渗层的表面硬度高达2197 HV,表面摩擦系数明显降低.极大地提高了材料的耐磨性.此外,高温氧化试验表明,渗钒层在400℃以下具有较强的抗氧化性能,有利于中低温下工作的工模具使用.     

Cr12MoV钢渗钒层组织及耐磨性能

为改善Cr12MoV钢耐磨性,提高其使用寿命,通过950℃×8hTD盐浴渗钒处理在Cr12MoV钢表面制备渗钒层。利用扫描电子显微镜、能谱仪、X射线衍射和摩擦磨损试验对渗钒层组织成分和磨损性能进行检测分析,结果表明:Cr12MoV钢表面渗钒层组织均匀致密,且覆层与基体间存在明显的界面,渗钒层厚度约为9.0μm。渗钒层主要物相由VCx相组成,碳化钒覆层具有(200)和(220)晶面择优取向。经渗钒处理后试样表面显微硬度可达2 002HV0.05,约为原始试样显微硬度值的2.88倍。用GCr15钢球作为摩擦副,载荷为4.9N,滑动速度为0.1m/s,磨损时间为30min条件下,渗钒层的摩擦因数约为0.58;渗钒后试样的磨损体积约为原始试样的0.29倍,其磨损的机制主要为粘着磨损。通过TD盐浴渗钒处理,在Cr12MoV钢表面制备碳化钒涂层可有效提高其耐磨性。     

Cr12MoV钢盐浴渗钛工艺研究

采用TD盐浴技术在小型井式盐浴炉中对Cr12MoV钢分别进行了硼砂盐浴渗钛、铬钛共渗、铬钛复合渗处理。用XRD对渗层的物相进行鉴定,用OM和SEM分析渗层组织,用显微硬度计测试渗层的显微硬度。结果表明:经盐浴处理后,Cr12MoV钢表面可以得到厚的渗层,硬度显著提高,硬度梯度不大。铬钛共渗和铬钛复合渗能得到少量不连续的Ti C覆层,而渗钛工艺只能得到渗硼覆层。     

Cr12MoV钢粉末TD渗钒层的显微结构及性能

采用TD粉末法对Cr12MoV钢进行渗钒处理,利用扫描电镜(SEM)、X射线能谱仪(EDS)、X射线衍射仪(XRD)对渗层的显微结构、元素分布以及物相组成进行了分析;同时,对渗层/基体间的界面结合力以及耐磨性和耐腐蚀性进行了研究。结果表明:Cr12MoV钢经1000℃×6h粉末渗钒处理后,比相同条件下采用盐浴法所制备的渗钒层的厚度明显增加,约为15μm;渗层连续、均匀且致密,渗层与基体间的界面结合方式为扩散冶金结合;渗层与基体间存在明显的过渡层,和盐浴渗钒层相比界面变得更不明显。XRD测试结果显示,渗钒层的主要物相为VC_x(x=0.83~0.88)以及少量的α-Fe,VC_x在(220)和(111)晶面上具有择优取向,而盐浴渗钒层通常在(111)和(200)两个晶面上择优取向。膜基结合力的测试结果表明渗钒层与基体之间的界面结合力约为65N。渗钒处理后试样表面硬度值为1950 HV0.3,约为原始基体的6倍。经粉末渗钒处理后,试样的耐磨性和耐腐蚀性均得到显提高。     

Cr12MoV钢低温盐浴渗铬复合处理

研究Cr12MoV钢低温复合盐浴渗铬处理后复合渗铬层的金相组织、相结构、渗层厚度、渗层硬度、铬浓度分布和氮碳浓度分布，并进行渗层的耐磨性对比试验。结果表明，Cr12MoV钢经氮碳共渗加低温盐浴渗铬复合处理可获得良好的渗铬层及优异的耐磨性。     

还原剂对钢表面被覆碳化钒的影响

采用硼砂盐浴的方法进行TD处理实验,研究了还原剂对Cr12MoV钢TD处理的影响。结果表明,如果没有还原剂,基体表面将没有碳化钒层生成;如果还原剂被加进盐浴,它会还原出活性原子。在基体表面形成碳化钒覆层。     

还原剂对钢表面被覆碳化钒的影响

采用硼砂盐浴的方法进行TD处理实验，研究了还原剂对Cr12MoV钢TD处理的影响。结果表明，如果没有还原剂，基体表面将没有碳化钒层生成；如果还原剂被加进盐浴，它会还原出活性原子，在基体表面形成碳化钒覆层。     

TD法混合盐浴渗钒在SDC99钢上的研究

对SDC99新型冷作模具钢的TD法盐浴渗钒配方进行了研究,确定出最佳的混合盐浴配方为75.6%硼砂+8.4%BaCl2+10%V2O5+6%Al粉。用该配方对SDC99钢进行950℃×4 h渗钒处理,能获得均匀、连续的碳化钒覆层。SDC99钢的碳化钒覆层与对比试验的Cr12MoV钢所获厚度相当,认为这是碳与钢中各种合金元素相互作用的结果。     

表面渗钒处理对SDC99和Cr12MoV钢摩擦磨损性能的影响

以SDC99和Cr12MoV钢为研究对象,通过对两种钢进行TD法(Thermal diffusion)表面渗钒处理,对比研究了两种钢经摩擦磨损试验后表面微观组织及成分的变化规律。结果表明,采用TD法对SDC99和Cr12MoV钢表面进行渗钒处理均可减少钢表面犁沟的数量、降低犁沟深度;磨损后SDC99钢表面的渗钒覆层并未磨穿,磨屑在环境温度和摩擦生热的共同作用下发生了氧化;较Cr12MoV而言,SDC99钢的耐磨性能更好。     

LD钢TD盐浴渗钒组织和性能研究

通过TD盐浴渗钒处理在LD钢表面制备渗钒层。利用扫描电子显微镜、能谱仪、X射线衍射仪对渗钒层组织成分进行检测。结果表明:经TD盐浴渗钒处理后,在LD钢表面获得较为均匀致密的渗钒层,覆层与基体为冶金结合。950℃时,覆层厚度和硬度随时间增长而增加;8 h覆层厚度约为6.1μm,显微硬度值约为1975 HV0.025。覆层主要由无序VCx相组成。LD钢在950℃碳化钒覆层生长动力学近似遵循ln=Dt(n2)方程。     

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。