AISI431不锈钢表面“膨胀”α相层的制备和性能

对AISI431马氏体不锈钢进行低温等离子体改性处理,通过金相观察、X射线分析等对渗层组织结构进行表征,利用显微硬度仪以及腐蚀极化曲线等对渗层硬度和耐蚀性能进行测试。结果表明,通过低温改性处理,均可在不锈钢表面获得含有"膨胀"α相的渗层,其中渗氮处理后表面主要含Fe4N和含氮"膨胀"α相,渗碳处理后表面主要为含碳"膨胀"α相,且渗氮层厚度明显大于渗碳层厚度。经低温改性处理后,不锈钢表面硬度显著提升,且渗氮层硬度高于渗碳层硬度。然而,在本试验条件下渗氮渗碳的不锈钢耐蚀性能均略有下降,和渗氮相比,渗碳处理后的试样耐蚀性能更差,且在腐蚀过程中,两类渗层表面所产生钝化膜均为具有n型半导体特性。     

2Cr13不锈钢活性屏等离子体源渗氮层组织与耐蚀性能

目的 探讨活性屏等离子体源渗氮技术提高马氏体不锈钢硬度与耐蚀性能的可行性。方法 将2Cr13马氏体不锈钢进行350～550℃、6 h活性屏等离子体源渗氮处理,采用光学显微镜（OM）、电子探针显微分析仪（EPMA）和X射线衍射仪（XRD）分析渗氮层的组织、成分和相结构,使用显微硬度计测试渗氮层的显微硬度,利用电化学腐蚀试验解析评估渗氮层的耐蚀性能。结果 经活性屏等离子体源渗氮处理后,可在马氏体不锈钢表面形成厚度为2～45μm,N原子分数为20%～25%的渗氮层,其表面显微硬度达1050～1350HV0.25,是基体硬度的4～5倍。350℃时,渗氮层以ε-Fe_2-3N相为主,且含有少量αN相;450℃时,渗氮层由αN、ε-Fe_2-3N和γ’-Fe₄N相构成;渗氮温度升至550℃时,渗氮层由α-Fe、CrN和γ’-Fe4N相构成,αN、ε-Fe2-3N相消失。350、450℃时,渗氮层在3.5%NaCl溶液中的阳极极化曲线出现明显钝化区,而未渗氮的2Cr13不锈钢并未发现钝化区,自腐蚀电位E_corr由未渗...     

AISI420不锈钢表面低温渗氮层组织结构和耐蚀性能

对AISI420不锈钢进行低温等离子体渗氮处理,采用金相观察、X射线分析等手段对渗层组织结构进行表征,利用显微硬度仪以及腐蚀极化曲线等对渗层硬度和耐蚀性能进行测试。结果表明,不锈钢表面渗层组织均匀,渗层厚度随着温度和时间的增加而增加,渗层表面主要由Fe_4N和少量的过饱和含氮α相组成。渗氮后,不锈钢硬度明显增加,且随着时间的延长,渗层硬度升高;渗氮4 h和8 h后的试样耐蚀性均略有下降,但处理12 h后的试样耐蚀性升高,且经渗氮处理后,不锈钢表面形成钝化膜的半导体特性由未处理不锈钢的p型转变为n型。     

2Cr13马氏体不锈钢活性屏离子渗氮技术

对2Cr13马氏体不锈钢分别进行常规直流离子渗氮和活性屏离子渗氮对比试验。渗氮温度均为440℃,渗氮时间为8 h。采用金相显微镜、扫描电镜、X射线衍射仪、表面粗糙度仪、显微硬度仪和电化学工作站等设备分析表征两种渗氮样品。实验结果表明:活性屏离子渗氮在避免了传统离子渗氮缺点的同时,取得了与其相同的硬化效果。可在马氏体不锈钢表面制备一定厚度的均匀致密的白亮层,其相结构是以ε-Fe_(2-3)N相为主,并伴随少量的αN相。马氏体不锈钢活性屏渗氮处理不仅可以提高表面硬度,而且获得了良好的耐蚀性能。     

低温离子硬化处理对AISI 420不锈钢组织与性能的影响

研究了低温离子渗氮、离子氮碳共渗和离子渗碳硬化处理对AISI 420马氏体不锈钢的显微组织、表面硬度、耐蚀性、耐磨性的影响。结果表明,离子渗氮、氮碳共渗和离子渗碳处理都可提高马氏体不锈钢的表面硬度;经不同工艺处理后的试样,除500 ℃×4 h渗氮工艺外,其他不锈钢试样表面的耐蚀性均未出现明显降低,当渗氮温度过高（500 ℃）时,由于CrN的析出使得渗氮层的耐蚀性显著下降;磨损试验的结果表明,离子渗碳处理后硬化层的耐磨性最佳。     

00Cr12Ni9Mo4Cu2Ti马氏体时效不锈钢离子渗氮组织和性能

对00Cr12Ni9Mo4Cu2Ti马氏体时效不锈钢进行了离子渗氮处理,研究了不同渗氮条件下所形成的渗氮层的相结构与性能。结果表明:经离子渗氮后的00Cr12Ni9Mo4Cu2Ti马氏体时效不锈钢的表面硬度、耐磨性都有明显的提高,表面硬度最高达到了1350HV0.05。当样品在400℃渗氮时,表层新相主要由α相组成;当渗氮温度上升至500℃时,表层新相主要由αN相、γ′-Fe4N相、ε相组成,并有大量的CrN相形成;当渗氮温度高于600℃时,ε相、CrN的含量继续增加,γ′-Fe4N相逐渐减少,αN相几乎完全分解。伴随着CrN相的生成,样品的耐磨性得到了提高,表面耐腐蚀性能有一定下降。实验还观察到该马氏体时效不锈钢渗氮层中有微裂纹产生,裂纹的形成与样品的残余内应力和氮化物相生成有关。     

离子渗氮工艺对S32205双相不锈钢综合性能的影响

在不同温度下对S32205双相不锈钢进行离子渗氮,利用光学显微镜、显微硬度计、电化学测试仪、XRD等对渗氮层组织性能进行分析。结果表明,400℃离子渗氮4 h工艺条件下,渗氮层由γN相构成,自腐蚀电位由基材的-0.294 V升高至-0.271 V,表面硬度可达到966 HV0.01,为基材表面硬度的2.5倍,渗氮层深为8μm,该温度下离子渗氮可同时提高S32205双相不锈钢耐蚀性和表面硬度。随着渗氮温度升高,在450℃和500℃渗氮时虽然渗氮层深和硬度明显提高,然而由于Cr N的析出,耐蚀性均低于基材。     

工件电位对奥氏体不锈钢活性屏离子渗氮的影响

用活性屏离子渗氮技术分别对处于悬浮电位和阳极电位的AISI 316L奥氏体不锈钢进行低温渗氮处理.并对渗氮层的组织、形貌、相结构、显微硬度和耐蚀性能进行分析.结果表明,在这两种电位状态下处理的试样均可获得具有S相结构特征的单相硬化层.渗氮层不仅具有高的硬度,还有良好的耐蚀性能.在活性屏离子渗氮过程中,从活性屏上溅射下来的中性S相粒子也可以起到氮载体的作用.活性屏空间中性粒子和电子的撞击足以消除不锈钢表面钝化膜对氮的阻隔作用.     

304不锈钢双活性屏离子渗氮

目的 考察304不锈钢双活性屏离子渗氮技术的可行性及处理效果.方法 利用双活性屏离子渗氮(DASPN)和普通直流离子渗氮(DCPN)两种技术对304不锈钢进行低温(420℃)硬化处理,对比分析两种工艺所得渗层的组织,对比研究两种工艺所得渗层的相结构、硬度和耐蚀性能.结果 采用DASPN技术可获得比采用DCPN技术更为均匀、致密的渗层,渗层为单一S相层,硬度为763 HV0.25.电化学测试表明,两种渗氮技术相比,DASPN处理获得的渗层耐蚀性能更优.结论 采用DASPN技术对304不锈钢进行低温硬化处理,在试样距双屏的距离为70 mm时能够获得比DCPN更好的渗氮效果.该技术适于工业化推广应用.     

离子渗氮马氏体不锈钢的微观组织与腐蚀行为

采用扫描电镜、X射线衍射(XRD)、极化曲线和显微硬度等方法研究表面离子渗氮X12Cr13马氏体不锈钢的渗氮层成分、显微组织结构、硬度以及腐蚀性能。结果表明:离子渗氮马氏体不锈钢表面形成了70μm的渗氮层,渗氮层由化合物层和扩散层组成,化合物层的组成相主要为γ-Fe N和ε-Fe N。离子渗氮不锈钢经过72 h纯水浸泡后表面发生点蚀。基体内部向表层的扩散降低了钢中的固溶铬含量以及渗氮层形成的孔隙和裂纹共同降低马氏体不锈钢的耐腐蚀性。     

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。