从渗硼层的结构和性能探讨渗硼的机制

用相同的渗硼工艺对45钢、T10钢和CrWMn钢进行了渗硼处理,观察其渗硼层的厚度和形态;对不同材料的渗硼试样进行淬火,对比其耐磨性能,探讨渗硼的机制,分析造成不同材料渗硼层的厚度、硬度及耐磨性不同的原因。     

强韧化65Mn钢低温稀土硼共渗层的组织和性能

在700℃下对强韧化处理(淬火-中温回火)后的65Mn钢进行了低温稀土硼共渗处理,研究了其表面渗层的微观形貌、耐磨性和耐蚀性,并与850℃下常规渗硼后再进行同样强韧化处理的65Mn钢进行了对比。结果表明:相对于常规渗硼后再进行强韧化处理而言,对65Mn钢先进行强韧化处理再进行低温稀土硼共渗处理所获得的渗层组织更加均匀致密,且未见常规渗硼后再进行强韧化处理所存在的表层及界面区疏松现象;同时,所获渗层在相同实验条件下的耐磨性和耐蚀性均得到明显提高,其体积磨损量仅为常规渗硼后再进行强韧化处理的17.86%,且无论在表面还是界面均未见腐蚀痕迹。     

热处理对65Mn钢表面渗硼层组织和性能的影响

研究淬火-中温回火和等温淬火两种热处理工艺对65Mn钢表面渗硼层组织和性能的影响。结果表明:经该工艺热处理后,65Mn钢表面渗硼试样呈现出典型的表硬芯韧组织特征,其表面为高硬抗磨的硼化物,芯部为强韧的回火屈氏体或下贝氏体;同时,渗硼层物相由以FeB相为主转变为以Fe2B相为主,虽硬度、耐磨性有所下降但其脆性降低了1～2个等级;此外,等温淬火处理在降低热处理应力、保持表面硬度及耐磨性和改善芯部强韧性等方面均好于淬火-中温回火处理。     

45钢低温气体多元共渗的研究

为提高机械零件的耐磨性和使用寿命,对45钢进行低温气体氮-碳-硼-稀土多元共渗.结果表明,45钢经多元共渗后,在材料表面形成较厚的化合物层和扩散层,稀土元素镧也渗入了钢的表面,起到微合金化的作用,使材料的耐磨性、得到明显提高.该工艺处理温度低、生产周期短、工件变形小、能源消耗低,且易实现和掌握.     

硬质合金热处理研究进展

综述了硬质合金热处理研究进展,普通硬质合金可通过淬火回火处理,渗硼碳及硼－镧共渗化学热处理,双重淬火回火处理,真空热处理,离子注入,激光热处理来提高其抗弯强度,表面硬度和耐磨性,断裂韧性等力学性能,钢结硬质合金可通过选择合适的淬火回火工艺,渗硼和硼－硫共渗化学热处理来提高合金的表面硬度,耐磨性和热疲劳抗力,从而达到提高硬质合金产品使用寿命的目的。     

激光淬火后Cr12MoV钢渗硼层界面形貌与能谱分析

利用热浸渗法对Cr12Mo V冷作模具钢进行渗硼处理,通过激光淬火对渗硼层进行了强化处理,用SEM、EDS、XRD对渗硼层表面-界面形貌、化学元素分布和物相进行表征,分析了激光淬火对渗硼层组织和性能的影响。结果表明,激光淬火后Cr12Mo V钢渗硼层表面孔洞减少,降低了剥落的可能性;激光淬火后渗硼层产生了Fe-Cr化合物和Fe2B新相,仍以Fe B相为主,有利于减少渗硼层脆性;元素未发生大量扩散,富碳层仍然存在,但组织得到细化,韧性和强度有所提高;激光淬火时孔洞中Si元素溶于奥氏体中,分布更均匀,Cr与Fe结合增强了渗硼层结合强度。     

45钢双层辉光离子渗Cr-C工艺的研究

在45钢表面利用双层辉光离子渗铬和双层辉光离子渗碳技术,形成高碳化物含量的合金层,对该合金化渗层进行淬火、回火及耐磨性的对比试验。结果表明,在本试验的工艺条件下,渗铬层可达数百微米以上;渗Cr-C+淬火回火后,渗层碳化物细小、弥散、均匀,渗层耐磨性达到了淬火回火G Cr15钢的7.8倍。     

稀土La2O3对45钢渗硼层性能的影响

目的研究渗硼剂中稀土氧化物La_2O_3的添加量对45#钢渗硼层厚度及性能的影响。方法通过在渗硼剂中添加质量分数为0%、5%、10%的La_2O_3,对45#钢在850℃进行4h渗硼处理,利用金相显微镜观察渗硼层的形貌并测试其厚度,利用XRD分析渗硼层的物相结构,利用显微硬度计、磨损试验机、电化学工作站对渗硼层的硬度、耐磨性、耐腐蚀性以及脆性进行测定及衡量。结果 45#钢渗硼后,硬度显著提高,且在渗剂中加入5%和10%的La_2O_3进行渗硼后,渗硼层厚度及硬度较渗剂中不加La_2O_3均有明显增加。在渗剂中添加不同含量的La_2O_3对渗硼层的耐磨性、耐蚀性以及脆性影响不同。添加5%La_2O_3进行渗硼后,渗硼层的耐磨性、耐蚀性最佳,脆性最小;添加10%La_2O_3进行渗硼后,渗硼层的耐磨性和脆性都比未加La_2O_3的要差,但耐腐蚀性较未加La_2O_3的要好。结论综合渗硼层的厚度、硬度、耐磨性、耐腐蚀性以及脆性指标,在渗硼剂中加入5%La_2O_3时,45#钢渗硼层厚度适中,性能最佳。     

激光辐照对渗硼后65Mn钢组织和性能的影响

采用激光辐照对渗硼后65Mn钢进行了表面改性,研究了激光重熔和激光淬火两种典型辐照处理后的微观组织、表层脆性和耐磨性。结果表明:65Mn钢渗硼试样,经激光重熔后其表层组织为夹杂着共晶硼化物的亚共晶组织(硬度约为880 HV),而经激光淬火后其表层组织是以Fe2B相为主的硼化物(硬度约为1100 HV),两种辐照处理后在次表层均形成了具有良好支撑作用的针状马氏体区;同时,两种激光辐照处理对表层脆性均有着较好的改善作用,脆性等级由原渗硼层的4级降低至1~2级;此外,经激光淬火后65Mn钢渗硼试样的耐磨性,不仅远好于激光重熔处理后的试样,而且也好于激光辐照处理前的渗硼试样。     

45钢双层辉光离子渗Cr-C工艺的研究

在45钢表面利用双层辉光离子渗铬和双层辉光离子渗碳技术，形成高碳化物含量的合金层，对该合金化渗层进行淬火、回火及耐磨性的对比试验。结果表明，在本试验的工艺条件下，渗铬层可达数百微米以上；渗Cr-C＋淬火回火后，渗层碳化物细小、弥散、均匀，渗层耐磨性达到了淬火回火GCr15钢的7．8倍。     

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。