低温离子渗氮时间对304不锈钢渗层的影响

对304奥氏体不锈钢进行400 ℃不同时间的离子渗氮处理.利用光学显微镜、轮廓仪、能谱仪、X射线衍射仪和显微硬度计研究了经渗氮处理后试样改性层的表面形貌、微观结构、相组成和性能等.结果表明,随着渗氮时间的延长,试样表面的粗糙度、渗层厚度、表面氮含量、显微硬度基本呈线性增加;X射线衍射分析表明,在400 ℃不同时间的渗氮层为单一S相,并无CrN相析出.     

离子渗氮温度对Fe-C-Cr-Ni-Mn-V沉淀硬化型奥氏体不锈钢渗层组织和性能的影响

采用离子渗氮工艺对一种Fe-C-Cr-Ni-Mn-V沉淀硬化型奥氏体不锈钢进行表面改性处理。利用光学显微镜(OM)、X射线衍射(XRD)、电子探针显微分析仪(EPMA)和维氏硬度计对不同离子渗氮温度下渗层的组织和性能进行了研究。结果表明,Fe-C-Cr-Ni-Mn-V沉淀硬化型奥氏体不锈钢经430~520 ℃离子渗氮处理10 h后,试样表面均形成一层厚度均匀的渗氮层,表面硬度显著增大。随着离子渗氮温度的升高,渗层厚度增大,520 ℃渗氮时渗层厚度达到78 μm。当渗氮温度为430 ℃时,渗层表面主要由γ_N+CrN+γ′-Fe₄N相组成;当渗氮温度升高至520 ℃时,渗层表面主要由γ′-Fe₄N+CrN+ε-Fe_2-3N相组成。在3种渗氮温度下,渗层中均有CrN析出,导致渗层耐蚀性低于基体组织。     

气压对304奥氏体不锈钢低温离子渗氮组织与性能影响

在400℃、8 h、不同气压(80~400 Pa)条件下对304奥氏体不锈钢进行离子渗氮处理。采用扫描电镜(SEM)、X射线衍射仪、显微硬度计及万能摩擦试验机对表面改性后的304奥氏体不锈钢渗层组织、相结构、渗层硬度以及耐磨性进行了测试和分析。结果表明,400℃离子渗氮处理后304奥氏体不锈钢形成了明显的白亮层,即单相S相层;低压对304奥氏体不锈钢离子氮化具有良好的催渗效果,即渗层厚度随气压的减小而增加,在100 Pa条件下,渗层厚度达到最大值51.7μm;渗氮后试样表面硬度达到最大值1100 HV0.01;低温低压离子渗氮能够提高304奥氏体不锈钢耐磨性,80 Pa和100 Pa是提高304奥氏体不锈钢耐磨性的最佳气压。     

低温氮化对1Cr11不锈钢耐双相流冲刷腐蚀性能的影响

为研究低温盐浴氮化提升马氏体钢耐冲刷腐蚀的机理,在410、430和450℃不同温度下对1Cr11不锈钢盐浴氮化8h。通过光学显微镜,X射线衍射分析仪(XRD),显微硬度仪对渗氮层的渗氮层厚度、显微组织及显微硬度进行研究,通过电化学工作站循环伏安法和双相流冲刷腐蚀模拟试验研究不锈钢耐蚀性。结果表明,渗氮层包括化合物层和扩散层,化合物层主要由N的过饱和固溶体αN和含氮化合物ε-Fe2-3N组成。渗氮层显微硬度约为基体硬度3倍;循环伏安法表明渗氮层和基体在NaCl溶液中均发生钝化,但渗氮层表面钝化膜在溶解后具有自我修复能力,抗点蚀能力好。经过120h的冲刷腐蚀模拟试验,氮化样品质量损失速率远低于未处理试样的质量损失速率,氮化可以有效提升试样的耐冲蚀性能。     

钛催渗低温离子渗氮对304不锈钢组织性能的影响

目的 在保障304奥氏体不锈钢良好耐蚀性前提下,研发显著改善表层硬度及耐磨性的低温高效离子渗氮技术。方法 低温离子渗氮时,在试样周围均匀放置微量海绵钛,研发304奥氏体不锈钢创新钛催渗低温离子渗氮技术。采用光学显微镜、扫描电子显微镜、能谱分析仪、X射线粉末衍射仪、显微维氏硬度计、摩擦磨损测试仪,以及电化学工作站等设备分别对试样截面显微组织、物相及成分、截面显微硬度、渗层耐磨性能、耐蚀性能等渗层组织性能进行测试与分析。结果 304奥氏体不锈钢在420 ℃/4 h钛催渗离子渗氮处理后,不仅保持了良好耐蚀性,且渗层耐蚀性比常规低温离子渗氮略有提升,同时,表面硬度与耐磨性大幅提高,表面硬度由常规离子渗氮的978HV0.025提升至1350HV0.025。磨损率由20.9 μg/(N.m)降低至7.4 μg/(N.m),下降了约2/3。特别有价值的是,钛催渗低温离子渗氮效率比传统离子渗氮显著提升,渗氮层厚度由常规离子渗氮的11.37 μm增厚到48.32 μm,即渗氮效率提高到常规离子渗氮的4倍以上。结论 本研究研发的钛催渗低温离子渗氮技术在保障304奥氏体不锈钢优良耐蚀性的同时,能够大幅度提升不锈钢表面硬度及耐磨性能,且具有显著的催渗效果。     

气压对904L奥氏体不锈钢低温离子渗氮组织与耐蚀性能的影响

通过辉光离子低温渗氮对904L超级奥氏体不锈钢(904Lss)进行表面改性处理,采用扫描电镜、X射线衍射仪(XRD)、电化学方法等研究了渗氮后试样的表面形貌、显微组织结构、硬度以及耐蚀性能。结果表明:100 Pa渗氮后的试样形成了强化相γN相,大大提高了904L不锈钢试样的表面硬度,高达1400 HV0.1;150 Pa渗氮后的试样产生了强氮化物CrN,其耐蚀性远远低于原始904L奥氏体不锈钢。     

双相不锈钢高温快速离子渗氮表面改性

在双相不锈钢等离子体渗氮表面改性过程中,为了避免N原子与Cr原子结合形成CrN的析出使基体中Cr元素含量减少进而降低双相不锈钢的耐蚀性能,通常渗氮温度选取低于450℃。温度低,N原子的扩散速率慢,存在渗氮时间长,渗氮层较薄等问题。对SS2205双相不锈钢在不同时间进行了高温快速离子渗氮研究,结果表明:在540℃条件下,渗氮时间为1h时,可得到8μm厚且没有明显CrN析出的渗氮层,使其表面硬度显著提高;与440℃、4h条件下得到的渗氮层相比,厚度增加了一倍,表面硬度提高50%左右,且耐点腐蚀性能并没有严重下降。     

QPQ盐浴复合处理时间对304不锈钢耐磨性的影响

利用光学显微镜、X射线衍射仪、显微硬度计、摩擦磨损试验机研究了304不锈钢在565℃进行60 ～ 180 min盐浴复合处理(QPQ)后对304不锈钢表面组织和耐磨性性能的影响.结果表明,在565℃渗氮时间为150 min时,304不锈钢硬度峰值约为1200 HV,比基体高5倍以上.工件经QPQ工艺处理后试样钢渗层结构由表及里为致密的氧化膜、渗氮层和扩散层,其中渗氮层主要物相为ε-Fe2-3N.耐磨性实验表明,QPQ处理可显著改善304不锈钢耐磨性.在565℃渗氮时间150 min为改善耐磨性的最佳时间,处理后试样的耐磨性比原始试样提高10倍左右.     

304奥氏体不锈钢低气压离子渗氮组织与性能研究

在400℃、低气压下对304奥氏体不锈钢进行低温低压离子渗氮处理。采用扫描电镜、显微硬度计及万能摩擦试验机对表面改性后的304奥氏体不锈钢渗层组织、硬度及耐磨性进行了测试和分析。结果表明:304奥氏体不锈钢低温低气压渗氮形成了明显的白亮层;低气压对304奥氏体不锈钢离子渗氮具有良好的催渗效果,即渗层厚度随气压的减小而增加,在100 Pa条件下,渗层厚度达到最大值51.7μm;渗氮后试样表面硬度达到最大值1100 HV0.01;低温低气压离子渗氮能够提高304奥氏体不锈钢耐磨性,80 Pa和100 Pa是提高304奥氏体不锈钢耐磨性的最佳气压。     

AISI 300系列奥氏体不锈钢渗氮层组织和性能研究

目的 在AISI 300系列奥氏体不锈钢表面制备单一S相渗氮层,提高该系列不锈钢渗氮层的硬度、抗磨损性能,对比揭示渗氮前后不锈钢的磨损机制。方法 采用低温辉光等离子渗氮技术(LTPNT)在AISI 300系列奥氏体不锈钢表面制备渗氮层。利用光学显微镜(OM)、扫描电子显微镜(SEM)、电子探针(EPMA)、X射线衍射仪(XRD)分析渗氮层的截面形貌、元素分布和物相组成;通过比磨损率和磨痕形貌分析渗氮层的摩擦学性能;利用电化学实验考察渗氮前后3种不锈钢的耐蚀性。结果 AISI 300系列奥氏体不锈钢经380 ℃、12 h处理后,其表面获得了厚度为15 μm左右、与基体致密结合、组织成分均匀的渗氮层;渗氮层的相结构主要为S相,无CrN相析出;经渗氮后,该系列不锈钢表面硬度均为1 100HV左右,较基体硬度提高了5倍左右;不锈钢基体的磨损机理为黏着和磨粒磨损,经渗氮后转变为氧化磨损和微切削;渗氮层的比磨损率约为不锈钢基体的1/20,抗磨损的能力得到显著提升;在25 ℃环境温度下渗氮后,304L、316L和321的自腐蚀电位下降,腐蚀电流密度增加,腐蚀速率加快,耐腐蚀性能稍有降低。通过对比腐蚀形貌发现,渗氮层仍具有一定的耐蚀性能。结论 通过LTPNT可以获得高硬度、组织均匀致密、结合强度高的渗氮层,渗氮层中S相的存在可以显著提高AISI 300系列奥氏体不锈钢的表面硬度、抗磨损能力,降低其摩擦因数和比磨损率,对延长不锈钢的服役寿命有着积极的作用。     

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).     

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.     

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.     

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。