AZ91镁合金化学镀镍前处理的工艺

研究了H3PO4+Na2MoO4、H3PO4+KMnO4和H3PO4+Na3PO4三种酸洗工艺以及NH4HF2活化工艺等前处理工艺对AZ91 HP镁合金化学镀的影响.通过金相实验及极化实验,结果表明,AZ91 HP镁合金经H3PO4+ Na3PO4酸洗后再经NH4HF2工艺活化处理后施镀,可获得表面光亮、结合力强和耐蚀性能较好的镍-磷镀层.镁合金酸洗处理后表面的平整程度会影响其化学镀层平整度和光亮度,而活化处理后表面的粗糙程度则影响镀层和基体的结合力.     

AZ91镁合金化学镀镍前处理的工艺（英文）

研究了H3PO4+Na2Mo O4、H3PO4+KMn O4和H3PO4+Na3PO4三种酸洗工艺以及NH4HF2活化工艺等前处理工艺对AZ91HP镁合金化学镀的影响。通过金相实验及极化实验,结果表明,AZ91HP镁合金经H3PO4+Na3PO4酸洗后再经NH4HF2工艺活化处理后施镀,可获得表面光亮、结合力强和耐蚀性能较好的镍-磷镀层。镁合金酸洗处理后表面的平整程度会影响其化学镀层平整度和光亮度,而活化处理后表面的粗糙程度则影响镀层和基体的结合力。     

锡青铜化学镀 Ni-P 合金工艺及镀层性能

目的在锡青铜基体上化学镀Ni-P合金镀层,提高锡青铜的耐磨性和耐腐蚀性。方法以酸性含锌活化液活化锡青铜试样,在相同的条件下实施化学镀,并对镀态试样进行不同温度(250,400,500℃)下的热处理。对比基体、镀态试样和热处理试样的性能,研究热处理温度对锡青铜化学镀Ni-P合金层微观结构、显微硬度、耐磨性和耐腐蚀性的影响。结果锡青铜表面形成了Ni-P合金镀层,并且镀层无孔隙缺陷,与基体结合良好,沉积速率较快,为10.00μm/h。经热处理后,镀层的微观结构由非晶态向晶态转变,在500℃热处理的镀层显微硬度最大,耐磨性最好。镀态镀层和经250℃热处理的镀层在10%HNO3溶液和10%H2SO4溶液(10%均为体积分数)中的耐腐蚀性明显好于锡青铜基体,镀态镀层在两种介质溶液中的腐蚀速率分别为0.225,0.146 mg/(cm2·d)。结论采用酸性含锌活化液活化锡青铜基体,可以在锡青铜表面制备出化学镀Ni-P合金镀层,且镀覆效果较好。这表明紫铜化学镀Ni-P合金工艺同样适用于锡青铜。     

NH_4HF_2对AZ31镁合金化学镀镍层性能的影响

采用增重法、精密pH计、扫描电镜(SEM)和动电位极化曲线测定和分析了镀液的镀速、镀液的缓冲性、镀层的表面形貌和镀层的耐蚀性,研究了不同浓度NH_4HF_2对AZ31镁合金化学镀镍层性能的影响.结果表明,NH_4HF_2的浓度影响镀液的镀速及缓冲性、镀层的形貌及耐蚀性.当NH_4HF_2的质量浓度为5～15 g/L时,镀速随浓度的增加递增,而当NH_4HF_2的质量浓度为15～25 g/L时,镀速随浓度的增加而减少;镀液缓冲性随NH_4HF_2浓度的增加而提高.当NH_4HF_2的质量浓度为15 g/L时,镀速达到最大值21.9μm/h;当NH_4HF_2的质量浓度为20 g/L时,镀层致密完整且阳极极化曲线的钝化电位区间最大,自腐蚀电流密度最小,因此,此时镀层的耐蚀性最好.     

AZ31镁合金化学镀镍镀层分析

以H_3PO_4+HNO_3酸洗与NH_4HF_2+H_3PO_4活化为前处理工艺,对AZ31镁合金进行化学镀镍研究。应用扫描电子显微镜(SEM)、能谱分析(EDS)、X射线衍射仪(XRD)与X射线光电子能谱分析仪(XPS)等方法对化学镀镍层进行形貌、成分分布、相结构以及元素分析。结果表明:化学镀镍层表面平整光亮,镀层为高磷非晶结构。化学镀镍层表面,镍主要以单质镍(26.75%)、NiO(32.96%)以及Ni(OH)_2(40.29%)形式存在,磷主要以单质磷(20.17%)、PO2-4(17.37%)以及PO_4~(3-)(62.46%)形式存在;化学镀镍层内部,镍基本为金属单质镍,磷主要以单质磷(74.11%)以及PO_4(2-)(25.89%)形式存在。     

镁合金表面化学镀 Ni-P 和 Ni-P-SiC 的对比

目的提高镁合金的耐磨性、耐蚀性,扩大其应用领域。方法采用"磷酸+钼酸铵酸洗→HF活化"的方法进行前处理,直接在AZ91D镁合金表面化学镀Ni-P合金镀层和Ni-P-SiC复合镀层。对两种镀层的表面和截面形貌、成分、结构、硬度、耐蚀性及耐磨性进行了系统比较。结果在Ni-P合金镀层中引入SiC粉末后,镀层的胞状颗粒细化,硬度提高至643HV,但其腐蚀电流密度有所增大。结论与Ni-P合金镀层相比,Ni-P-SiC复合镀层的耐蚀性有所下降,但耐磨性能大大提高。     

一种无铬低氟的镁合金化学镀镍前处理工艺

为了获得一种更加环保的镁合金化学镀镍前处理工艺,通过多种方法和手段对比研究了3种不同的酸洗活化工艺对镁合金化学镀镍的影响。通过开路电势-时间(OCP-t)曲线解释了不同前处理方法导致不同沉积速度的原因。采用SEM、EDX和XRD分析发现,3种工艺所得镀层均为高磷合金镀层(P含量约为11%),镀层的表面形貌和结构比较接近。动电位极化曲线表明,采用H_3PO_4+HNO_3酸洗,K_4P_2O_7和NH_4HF_2分别活化的前处理工艺所得镀层耐蚀能力略优于传统工艺镀层。新工艺酸洗液对镁合金存在横向的刻蚀,可增强镀层与基底间的机械咬合作用,使得镀层的结合力更强。     

AZ91D镁合金低温快速化学镀Ni-P工艺的研究

采用化学镀方法,在AZ91D镁合金上沉积Ni-P镀层,研究了添加剂对镀层的影响.结果表明:未加添加剂时,沉积速度慢;加入添加剂后,镀层的沉积速度增加,65℃时只需30min就可获得无气孔或裂纹、具有“菜花状”结构的均匀完整的Ni-P镀层.XRD测试结果表明,沉积的Ni-P镀层为非晶态.镀层的耐蚀性实验结果表明,化学镀Ni-P镀层后,AZ91D镁合金的耐蚀性优于基体.     

AZ91D镁合金的化学镀镍

使用硫酸镍作为化学镀镍磷镀液的主盐,直接在AZ91D镁合金基体上化学镀镍.使用扫描电镜和X射线衍射技术分析镀层的表面形貌和组织.化学镀镍磷镀层是致密的,无明显缺陷,其磷含量约为372 mass%.化学镀镍磷镀层的显微硬度值约为660 VHN,化学镀镍的沉积速度为23 μm/h.前处理过程中的酸洗步骤使镁合金基体产生粗糙的表面,从而使镀层和基体之间起到了互锁的作用,增加了镀层的结合力.     

磷化处理对AZ63镁合金化学镀Ni-P的影响

为了提高AZ63镁合金表面化学Ni-P镀的质量,本文在AZ63镁合金表面分别进行了Mn系和Zn系磷化处理,然后进行化学镀Ni-P的研究,利用扫描电子显微镜(SEM)、能谱仪(EDS)等测试方法分析镍磷镀层的形貌、成分、镍磷含量和耐蚀性得到以下结论:AZ63镁合金经Mn系或Zn系磷化处理后化学镀均可得到致密、厚度均匀的Ni-P镀层,Ni-P镀的速率达到25 um/h以上;Zn系磷化中间层化学Ni-P镀的镀速高于Mn系磷化中间层的化学Ni-P镀速。磷化处理的中间层主要影响Ni-P镀层的P的含量,非晶态结构,镀层硬度和耐蚀性;Ni-P镀层中P含量越低,耐蚀性越差。     

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.     

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.