304不锈钢Na2SO4电解酸洗工艺的研究

在分析Na2SO4电解酸洗机理的基础上,试验研究了电解酸洗的影响因素（如电流密度、电解液浓度和电解液温度）,并提出热轧304带钢最优电解酸洗工艺。试验结果表明,采用15％浓度的Na2SO4溶液,溶液温度为75 ℃,电流密度4 A/dm2 ,阳极处理时间10 s,阴极处理时间为阳极时间2倍的电解工艺可有效去除304不锈钢表面氧化皮。     

电解质等离子体抛光316LVM表面形貌及电化学特性

目的 研究电解质等离子体抛光对316LVM植入物不锈钢表面形貌及其在磷酸缓冲盐溶液中的电化学特性的影响,解决复杂形状植入物表面抛光难题.方法 原材料经线切割及表面预处理,制成20 mm×15 mm×3 mm的试验样件.对试样分别进行机械抛光及电解质等离子体抛光.机械抛光在砂带抛光机上进行,使用600、800、1200、2000、5000目的砂带逐级磨抛.电解质等离子体抛光中,电压为300 V,电解液为3％(质量分数)(NH4)2SO4水溶液,温度为85～90℃,抛光时间为15 min.通过粗糙度仪、扫描电镜,对试样表面粗糙度、微观形貌进行测试表征.通过能谱仪、X射线衍射仪,对试样表面元素含量、物相组成进行测试表征.通过电化学工作站,对磷酸缓冲盐溶液中的试样,进行电化学测试.结果 电解质等离子体抛光后,试样表面粗糙度由初始的0.5μm降至0.089μm,试样表面机械加工痕迹被去除,平整光亮.机械抛光后,试样表面化学元素未发生明显变化,而电解质等离子体抛光后,试样表面的Fe、Cr含量升高.机械抛光表面的X射线衍射峰位置和强度未发生明显变化,电解质等离子体抛光后,在衍射角为43.5°处,衍射峰强度明显降低,在74.5°处,衍射峰强度明显升高,同时各峰的半高宽明显减小.在磷酸缓冲盐溶液中,机械抛光试样的自腐蚀电位由-0.252 V升高至-0.232 V,腐蚀电流密度由1.611μA/cm2降低至0.5867μA/cm2,极化电阻由28.876 k?升高至64.682 k?.电解质等离子抛光试样的自腐蚀电位由-0.252 V升高至-0.214 V,腐蚀电流密度由1.611μA/cm2降低至0.1582μA/cm2,极化电阻由28.876 k?升高到251.262 k?.结论 电解质等离子体抛光可有效降低316LVM表面的粗糙度,提高表面平整度.电解质等离子体抛光后,表面Fe、Cr元素的含量升高,晶粒尺寸增大,呈(220)晶面择优取向.电解质等离子体抛光可提高316LVM在磷酸缓冲盐溶液中的耐腐蚀性能.     

轧制纳米块体304不锈钢腐蚀行为的研究Ⅱ钝化膜保护性能

采用动电位极化曲线和Mott-Schottky分析等电化学测试手段,探讨了轧制纳米块体304不锈钢与普通304不锈钢在0.05mol/L H2SO4＋0.05mol/L Na2SO4溶液中钝化膜的保护性能;运用点缺陷（PDM）模型,分析了不同电位下在0.05mol/L H2SO4＋0.25mol/L Na2SO4溶液中两种材料形成钝化膜的半导体性质,阐述了导致两种钝化膜保护性能差异的根本原因.结果表明：两种材料表面钝化膜都具有n型半导体特征,氧空穴作为主要的载流子参与钝化膜的形成和溶解过程;钝化膜中载流子密度与钝化膜的形成电位之间满足幂指数关系,载流子在两种材料表面的钝化膜中的扩散系数非常接近,说明两种钝化膜遵从相似的形成和溶解机制,但轧制纳米块体304不锈钢中的载流子密度小于普通304不锈钢钝化膜中的载流子密度,从而使其钝化膜具有更好的保护性.     

钛合金结构件磁流变电解复合抛光试验研究

目的 针对钛合金结构件高质高效抛光需求，提出了磁流变电解复合抛光新方法，探究不同抛光参数对钛合金表面质量的影响，以实现钛合金构件的高质高效抛光。方法 深入探究了加工电压、加工间隙、电解质质量分数和抛光转速等参数对钛合金抛光表面粗糙度以及粗糙度变化率的影响，分析了不同抛光参数下的钛合金表面形貌变化，验证了磁流变电解复合抛光钛合金的可行性。结果 随着电解液中Na NO3质量分数的提高，钛合金表面粗糙度先减小后增大，质量分数为1.0%～2.5%时，得到了优于单磁流变抛光加工的抛光效果。不同加工电压下的表面粗糙度对比结果表明，在加工电压为0.1 V时，钛合金加工后表面粗糙度达到最小，而后随着加工电压的增大，加工区域表面粗糙度呈现增大趋势；随着加工间隙的增大，钛合金抛光表面粗糙度呈现先减小后增大的趋势；随着抛光工具转速增大，钛合金加工后表面粗糙度先减小后增大。相比于单一的磁流变抛光，磁流变电解复合抛光钛合金90 min，可使表面粗糙度从初始323 nm降低至15nm，加工效率提高了62.5%。结论 磁流变电解复合抛光工艺能够用于钛合金人工关节假体高效高质量的抛光。     

304不锈钢在硝酸盐及硫酸溶液中的钝化

利用电化学方法和表面分析技术研究了304不锈钢在 硝酸盐及硫酸溶液中的钝化行为.结果表明，304不锈钢经硝酸盐及硫酸溶液中钝化后在3.5%NaCl溶液中的耐蚀性大为提高.SEM分析表明，经过H2SO4+KNO3钝化后，钝化膜具有网状的结构，膜层结合紧密；而单独在H2SO4溶液中钝化后，表面为有裂纹的钝化膜，微孔较多；单独在KNO3溶液中钝化，与未处理的基本相同.     

电解液加工性能实验报告(三) 含氧酸盐的抑制作用及应用

我们把在电解加工条件下,阳极表面生成绝缘性钝化膜的现象,称为抑制作用;而绝缘性钝化膜称为抑制膜;能在阳极生成绝缘钝化膜的电解液,称为抑制膜电解液。由于阳极生成抑制膜,显然对电解加工工艺是不适用的。但是对于要求成形精度很高的复合法电解磨削工艺,由于其电解——机械刮削的特点,由于抑制膜的绝缘保护作用,抑制膜电解液从理论上是理想的,实践也证明电解磨削性能是良好的。同时对金属阳极化表面处理(如防腐、绝缘处理),也具有一定的参考、应用价值。     

高速磨粒流动辅助电解复合加工方法

针对难加工材料表面抛光难、工具损耗严重、加工效率低的问题,提出了一种高速磨粒流动辅助电解加工的方法,通过在电解液中添加微小磨粒,伴随电解液高速流动实现电化学溶解与钝化膜微量磨削的复合加工。针对该方法的加工参数进行了分析,研究了加工时间、加工电压、加工间隙、电解液浓度、电源种类、磨粒粒径对实验结果的影响。结果表明:采用5 V电压的直流电源,以质量分数10%的NaNO3作为电解液,设定加工间隙1 mm,用1200目的磨粒加工5 min,可得到表面质量较好的工件,表面粗糙度Ra<0.1μm。     

SLM零件的磨粒流动辅助电化学复合抛光方法研究

针对增材制造金属零件表面质量较差的问题，提出一种磨粒流动辅助电化学复合抛光方法，在电解液中混入微小磨粒，使混合液在一定压力下流经工件表面，通过磨粒磨削和电化学溶解的复合作用改善工件表面质量。通过试验对比了纯磨粒磨削、纯电解加工和复合抛光的加工效果，分析了不同工艺参数对工件表面粗糙度和材料去除量的影响。试验结果表明：复合抛光方法能有效去除增材制造零件表面缺陷，改善其表面质量。通过选取合适的电压进行分阶段抛光，SLM工件的表面粗糙度由Ra8.162μm降至Ra1.226μm。     

表面粗糙度对硝酸钝化304不锈钢点蚀行为影响

采用动电位扫描、电化学阻抗谱和电化学噪声等方法研究了不同表面粗糙度的304不锈钢在体积分数10%HNO3溶液中钝化后的耐蚀性。结果表明,随304不锈钢钝化前表面粗糙度从0.25μm降到0.10μm,电荷转移电阻从6.51kΩ·cm2上升到19.17kΩ·cm2,电位标准偏差和电流标准偏差降低,而噪声电阻增大;随表面粗糙度的增大,试样电位和电流的功率密度曲线线性部分的斜率均出现增大,谱噪声曲线线性部分的斜率下降,表明在光滑的不锈钢表面更容易形成致密稳定且耐腐蚀性强的氧化膜,硝酸钝化能显著改善304不锈钢耐点蚀性能。     

电解质等离子抛光在高碳微合金钢上的应用研究

目的提高金属针布产品(高碳微合金钢)的表面质量,降低针布产品的表面粗糙度值,有效提升产品的使用效果。方法采用电解质等离子抛光工艺在针布产品上展开工艺研究,探索了不同电解质浓度(无机盐质量分数)、不同生产速度和不同电解质等离子抛光单元组数对针布表面粗糙度的影响。利用非接触式粗糙度扫描仪测试粗糙度Ra,以此对针布表面的抛光质量进行表征。结果采用电解质等离子抛光工艺可以实现钢铁材料的表面抛光,抛光后不仅有效地去除了针布表面的氧化皮,并且表面平整且达到镜面效果。最佳工艺参数(电解质无机盐质量分数2.75%,走线速度40 m/min,电解质等离子抛光单元4组)下,表面粗糙度Ra值达到了0.11μm。结论电解质等离子抛光工艺成功地应用于钢铁材料上,且实现了非接触式连续抛光工艺,既不损伤工件,又实现了表面的光亮平整,还具有环境友好、节能和生产效率高等特点。     

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.     

Growth Kinetics of Single Inclusion Particle in Molten Melts

On the basis of the single-particle framework, a new theory on inclusion growth in metallurgical melts is developed to study the kinetics of inclusion growth on account of reaction and collision. The studies show that the early growth of inclusion depends on reaction growth and Brawnian motion collision, and where the former is decisive, the late growth depends on turbulence collision and Stokes＇ collision, and where the former is dominant; collision growth is very quick during the smelting process, lessened in the refining process, but nearly negligible in the continuous casting process.     

Theoretical Analysis for the Motion and Temperature of Melt Droplets in Spray Degassing Process

The motion of melt droplets in spray degassing process was analyzed theoretically. The height of the treatment tank in spray degassing process could be determined by the results of theoretical calculation of motion of melt droplets. To know whether the melt droplets would solidify during spraying process, the balance temperature of melt droplets was also theoretically analyzed. Then proof experiments for theoretical results about temperature of melt droplets were carried. In comparison, the experimental results were nearly similar to the calculation results.     

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.