激光熔覆Ni2Si／Ni3Si2金属硅化物合金涂层显微组织与耐蚀性

以Ni76Si24（质量百分数）合金粉末为原料，利用激光熔覆技术在A3钢表面制得了组织由条件Ni2Si初生相及少量Ni2Si/Ni3Si2共晶组成的新型金属硅化物合金涂层，分析涂层显微组织并测定其在0．5mol/1 H2SO4水溶液及不同浓度NaCl水溶液中的阳极极化曲线，结果表明激光熔覆Ni2Si/Ni3Si2金属硅化物合金涂层表面平整，组织细小，与基体为完全冶金结合，同时由于涂层的组织组成相Ni3Si2本身均具有极好的耐蚀性并具有快速凝固细小均匀的显微组织，该激光熔覆Ni2Si/Ni3Si2金属硅化物合金涂层在0．5mol/l H2SO4及3．5％NaCl水溶液中均具有优良的耐蚀性能。     

Si3N4/Ni/TiAl扩散连接接头界面结构及性能

采用厚度为80 μm的镍中间层实现了Si3N4陶瓷和TiAl合金的扩散连接.采用扫描电镜(SEM),能谱检测(EDS)等分析方法确定了TiAl/Ni/Si3N4扩散焊接头的典型界面结构为TiAl/Al5Ni2Ti3/AlNi2Ti/Ni3(Ti,Al)/Ni(s,s)+Ni3Si/Si3N4.重点分析了连接温度对接头界...     

激光熔覆Ni-Si金属硅化物复合材料涂层显微组织与耐蚀性

以Ni,Si,Cr元素粉末为原料 ,利用激光熔覆技术在A3钢表面制得了Ni Si金属硅化物复合材料涂层。分析了该涂层的显微组织 ,采用测定阳极极化曲线的方法评价了该涂层在 0 .5mol/LH2 SO4 及 3 .5 %NaCl水溶液中的耐蚀性能。结果表明 :激光熔覆Ni Si金属硅化物复合材料涂层组织由Ni2 Si初生胞状树枝晶及枝晶间少量FeNi/Ni31Si12 共晶组成 ,涂层表面平整、组织细小、与基体间为完全冶金结合 ;涂层组织显微硬度在HV80 0～ 95 0之间且沿层深分布均匀 ;由于涂层组织组成相Ni2 Si和Ni31Si12 等本身均具有很好的耐蚀性并具有快速凝固细小均匀的显微组织 ,激光熔覆Ni Si金属硅化物复合材料涂层在 0 .5mol/LH2 SO4 及 3.5 %NaCl水溶液中均表现出优良的耐蚀性能。激光熔覆Ni Si金属硅化物复合材料涂层可望成为一种很有发展前景的耐蚀涂层新材料。     

CeO2对渗Si层组织和耐磨性能的影响

采用料浆包渗法,以SiO2粉为Si源,纯Al粉为还原剂,NaF和NH4Cl作为复合活化剂,Al2O3为惰性添加剂,蛋白质(鸡蛋清)为粘结剂,在Cu表面预先镀Ni层随后900℃、12h表面渗Si,制备渗Si层.分别研究了CeO2和Al粉含量对渗Si层组织和摩擦性能的影响.结果表明:当铝粉含量20％时,CeO2含量由3％增加到6％,渗层组织为Ni2Si+ NiSi相;当CeO2含量6％时,铝粉含量由20％增加到30％,渗层组织变化过程:Ni2Si+ NiSi→NiAl→Ni2Al3相,包渗过程由渗硅向渗铝转变;两种渗层的最小摩擦系数都约为纯铜的1/5.     

氩弧熔覆TiC-Ni3Si/Ni基复合涂层组织与性能研究

用X射线衍射仪、扫描电镜、显微硬度计和摩擦磨损试验机研究了采用氩弧熔覆技术制备的TiC-Ni3Si/Ni基复合涂层的组织与性能.结果表明,氩弧熔覆的TiC-Ni3Si/Ni基复合涂层主要由TiC、Ni3Si、γNi(Fe)过冷奥氏体相组成,TiC硬质颗粒和以TiC为核心原位生成的Ni3Si相弥散分布在镍基粘结相中.显微硬度和摩擦磨损实验表明,TiC-Ni3Si/Ni基复合涂层平均显微硬度9.457 GPa,是基体平均显微硬度的4.78倍,在常温千滑动磨损条件下,TiC-Ni3Si/Ni基复合涂层磨损量约为同等摩擦磨损条件下Q235钢磨损量的11.84％.     

Ti2Ni3Si/NiTi金属间化合物合金在H2SO4溶液中的腐蚀行为

利用激光熔炼材料制备技术,制得了由三元金属硅化物Ti2Ni3Si初生枝晶和枝晶间Ti2Ni3Si/Ti共晶组成的金属间化合物耐磨耐蚀合金;采用极化曲线、塔菲尔图(Tafel Plot)和交流阻抗(EIS)等技术,研究了合金在1 mol/L H2SO4溶液中的电化学腐蚀行为以及Ti含量对合金组织与耐蚀性的影响.结果表明:由于表面形成的稳定钝化膜及Ti2Ni3Si和NiTi的高化学稳定性,使合金在1 mol/L H2SO4溶液中具有优异的耐蚀性,且随着Ti含量的升高,合金的耐蚀性略有提高.     

化学镀镍层与Si3N4陶瓷的界面反应

采用真空加热和辉光离子轰击加热两种方式,对化学镀镍Si3N4陶瓷进行扩散热处理,并利用X射线衍射仪分析和讨论了化学镀Ni层与Si3N4的界面反应.分析表明,辉光离子轰击扩散能够显著促进镀Ni层与Si3N4的界面反应,其界面反应产物为Ni2Si、Ni3Si和Ni5Si2.随着扩散热处理温度的提高,反应产物的数量明显增加.处理前后,化学镀镍Si3N4陶瓷与金属钎焊接头剪切强度可由70mPa提高至123mPa.     

直接氮化法制备Si3N4粉体过程研究

采用直接氮化的工艺方法,以Si粉为初始原料,采用Fe粉为催化剂,在高温下直接进行氮化,制备了Si3N4粉体.着重讨论了催化剂含量和氮化工艺条件对粉体的氮化率、粒径、形貌和相含量等方面的影响.实验结果表明催化剂含量,球磨工艺,烧结制度是影响Si3N4粉体最终性能的3个主要因素,并且在掺杂Fe为0.5%,球磨时间为2h,采用分阶段保温升温的方法,在氮化温度为1400～1350℃下氮化2～3 h,制备了氮化率95%左右,α相含量接近90%,形状为等轴状的Si3N4粉体.     

Si_3N_4/Ni和Si_3N_4/Ni_3Al的界面固相反应

使用扫描电子显微镜、电子能谱仪、X射线衍射等研究了在N2气氛中1150℃×10 h等温热处理的Si3N4/Ni,Si3N4/Ni3Al平面偶界面固相反应区的形貌、成分分布、显微结构及相组成。结果表明:Si3N4/Ni界面固相反应形成约20μm厚的反应区,反应区主要由Ni3Si构成,其中分布着大量细密的孔洞;而Si3N4/Ni3Al界面固相反应形成约2μm厚的反应区,反应区具有比Ni3Al高得多的Al含量,反应区由NiAl及Ni3Si构成。Si3N4/Ni3Al具有比Si3N4/Ni高得多的界面化学相容性。     

免烧成低密度Si_3N_4/SiC复相耐火材料的制备及性能研究

针对氮化烧成Si_3N_4/SiC复相耐火材料的成本高、能耗大及传热损失大的突出问题,研究制备了免烧成低密度Si_3N_4/SiC复相耐火材料。研究以硅藻土作为硅源,蔗糖作为碳源,通过碳热还原氮化法制备了Si_3N_4/SiC复相粉体。再以该复相粉体为原料,以添加不同量Si粉(0%,5%,10%)的蔗糖作为结合剂,分别在60、90、120℃3个温度点热处理2 h,150℃热处理8 h后,制备成免烧成低密度Si_3N_4/SiC复相耐火材料。采用XRD和SEM对粉体的物相及微观形貌进行表征。结果表明:粉体的物相为α-Si3N4,β-Si3N4,β-Si C和Fe3Si,通过计算得到α-Si3N4,β-Si3N4和β-Si C的相对含量分别为4.28%,29.74%和59.40%;硅藻土中含有较高含量的Fe杂质元素导致少量Fe3Si生成;粉体中β-Si3N4呈短柱状,β-Si C以细小颗粒的形式存在。在N2(99.999%)保护条件下,1000°C模拟使用这种Si_3N_4/SiC复相耐火材料1h后发现,Si粉的添加量对其体积密度和显气孔率的影响不大,体积密度变化范围是1.48~1.51g·cm-3,显气孔率变化范围是33.36%~34.62%;Si粉添加量为5%时,材料的抗折强度和抗压强度达到最大,分别为3.78和31.95 MPa。     

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。