TiAl合金表面阴极微弧沉积Al_2O_3陶瓷涂层的生长过程与相组成

利用阴极微弧沉积技术在预处理后的TiAl合金表面制备了Al_2O_3陶瓷涂层,研究了涂层的生长过程和相组成。采用扫描电子电镜(SEM、EDS)、透射电子电镜(TEM)、X射线衍射(XRD)等方法,对Al_2O_3涂层的生长过程中的微观形貌、组织成分以及晶体结构的演变进行了研究与分析。结果表明,TiAl合金表面阴极微弧沉积过程中,在阴极表面发生非晶态Al(OH)3的吸附、脱水烧结形成Al_2O_3陶瓷涂层的沉积。Al_2O_3涂层生长分前期I、中期II和后期III 3个阶段,前期起弧阻挡层被击穿,涂层生长较慢、组织致密且与基体结合良好;反应中期涂层生长较快,Al(OH)_3不断吸附和脱水烧结,涂层结晶度提高;反应后期涂层生长速度变缓,表层组织疏松、多孔,相组成为87.5%的α-Al_2O_3和12.5%的γ-Al_2O_3。     

海洋钢微弧氧化膜层组织与性能

采用激光熔覆与微弧氧化技术相结合在S355海洋钢表面制备了复合陶瓷膜层,运用扫描电子显微镜(SEM)、能谱仪(EDS)和X射线衍射仪(XRD)表征陶瓷膜层的微观结构,通过涂层结合力、显微硬度、残余应力、摩擦磨损和电化学等测试方法研究复合膜层的性能。结果表明:复合陶瓷膜层主要由内致密层和外疏松层组成,疏松层主要由γ-Al_2O_3组成,致密层主要由α-Al_2O_3组成。随着电流密度增大,膜层厚度与微孔孔径逐渐增大。复合膜层与基底层结合良好,其硬度较熔覆涂层的有明显提升。熔覆涂层表面残余应力为拉应力,复合膜层均为压应力。在电流密度为5 A/dm~2时,复合膜层能明显改善基体与熔覆涂层的耐磨性与耐蚀性。     

表面改性对YZAlSi11Cu3铝合金耐磨性能的影响

研究了微弧氧化电流密度、频率对YZAl Si11Cu3压铸铝合金表面涂层物相组成、表面形貌、摩擦系数和磨损形貌的影响。结果表明,不同微弧氧化电流密度的涂层均由γ-Al_2O_3、α-Al_2O_3以及基体Al相组成;随着电流密度的增加,涂层中α-Al_2O_3衍射峰逐渐增强,而基体Al相衍射峰逐渐减弱;从涂层形貌、摩擦系数、磨损形貌和磨损失重来看,适宜的电流密度为10 A/dm2;不同微弧氧化频率下涂层的物相也为γ-Al_2O_3、α-Al_2O_3以及Al相,随着频率的增加,涂层中α-Al_2O_3衍射峰的强度逐渐减弱,而Al相衍射峰逐渐增强;600 Hz时涂层的磨损失重为0.1 mg,而1 000 Hz时涂层的磨损失重为0.3 mg,磨损失重的测量结果与磨损形貌保持一致,对磨损失重而言,适宜的微弧氧化频率为600 Hz。     

α-Al_2O_3层厚度对TiN/TiCN/Al_2O_3/TiN涂层抗氧化性能的影响

为获得抗氧化性能更为优越的TiN/TiCN/Al_2O_3/TiN复合涂层,本文采用中温化学气相沉积(MT-CVD)在WC-Co硬质合金基体表面沉积不同厚度α-Al_2O_3层的TiN/TiCN/Al_2O_3/TiN多层涂层,并在1 000℃下对涂层试样进行氧化实验。通过X射线衍射仪(XRD)和扫描电子显微镜(SEM)等手段研究α-Al_2O_3层厚度对TiN/TiCN/Al_2O_3/TiN涂层抗氧化性能的影响,确定可显著提高涂层抗氧化性能的α-Al_2O_3层厚度,同时探索涂层的抗氧化机理。结果表明:随着α-Al_2O_3层厚度的增加,TiN/TiCN/Al_2O_3/TiN多层涂层试样氧化后质量增量减少,涂层氧化增厚降低。当α-Al_2O_3层厚度为6.5μm时,TiN/TiCN/Al_2O_3/TiN涂层的抗氧化性能显著提高。随着涂层厚度的增加,涂层阻止O向涂层内部扩散及Al、Ti向外部涂层扩散能力增强,抗氧化性能更优越。     

ZL303铝合金表面微弧氧化陶瓷膜的微结构和耐蚀性研究

为提高ZL303铝合金耐蚀性能,采用微弧氧化技术在ZL303铝合金表面制备陶瓷质氧化膜。通过扫描电镜观察了微弧氧化膜层表面及截面的微结构。利用X射线衍射仪分析了膜层的物相组成。采用腐蚀电化学和高温浸泡实验测试了微弧氧化膜层的耐蚀性。结果表明:所制备的膜层厚度约为13μm,主要由α-Al_2O_3和γ-Al_2O_3组成,外表面存在大量微米级等离子放电微孔。经微弧氧化处理后,试样的电化学阻抗半径增大,自腐蚀电位上升,腐蚀电流密度减小。在高温腐蚀环境中,微弧氧化膜层能有效阻挡腐蚀介质对铝合金基体的侵蚀破坏,耐蚀性能得到提高。     

占空比对TiAl合金表面阴极微弧沉积Al2O3涂层的影响研究

目的通过调整实验工艺,研究占空比对Ti Al合金表面阴极微弧沉积过程的影响规律和作用机制。方法对Ti Al合金进行预处理后,在不同占空比条件下,于Al(NO3)3电解液中制备阴极微弧沉积Al_2O_3陶瓷涂层。采用电子扫描电镜(SEM)、元素能谱分析(EDS)、透射电子电镜(TEM)以及X射线衍射(XRD)等分析测试技术,对不同陶瓷涂层的微观组织结构和成分进行了分析,并使用涡流测厚仪、表面轮廓仪、维氏硬度计和划痕仪等材料性能测试设备,对涂层厚度、粗糙度、硬度、结合强度等力学性能进行了表征。结果在沉积过程中,占空比主要影响试样表面非晶态Al(OH)3的沉积吸附和脱水烧结以及晶体Al_2O_3的形成。随占空比增加,陶瓷涂层内部晶体结晶度提升,表面缺陷和微裂纹减少,均匀性、致密性和表面硬度均有所提高,厚度和结合强度先增加后降低,而表面粗糙度则呈现先降低后增加的趋势。结论占空比为30%时,涂层表面缺陷较少,与基体结合良好,涂层晶格条纹整齐,由α-Al_2O_3、γ-Al_2O_3和少量金红石相rutile-TiO2以及非晶相的Al(OH)3组成,α-Al_2O_3质量分数为89.0%,涂层厚度为47μm,表面粗糙度为1.0μm,结合强度为72 N,硬度为1010 MPa(HV200)。     

添加TiO_2和ZrO_2对火焰热喷涂Al_2O_3涂层性能的影响（英文）

采用火焰热喷涂技术在低碳钢表面上沉积制备添加25%ZrO_2(简称AZ-25)和3%TiO_2(简称AT-3)增强体的Al_2O_3涂层,对涂层的显微组织、相组成、显微硬度和摩擦学性能进行了研究。X射线衍射(XRD)结果表明,AT-3涂层的主要相组成为α-Al_2O_3,此外还含有一些亚稳的β-Al_2O_3和κ-Al_2O_3相。而AZ-25涂层的主要相组成为α-Al_2O_3,还有一些q-ZrO_2和m-ZrO_2相。在大多数实验条件下,AT-3涂层的摩擦学性能(摩擦因数、磨损率)均比AZ-25涂层要好。添加ZrO_2增强体会导致涂层的显微硬度降低,而添加TiO_2会使涂层硬度增加。     

微弧氧化制备氧化铝阻氚涂层的研究（英文）

采用微弧氧化技术在316L不锈钢基体上制备了氧化铝阻氚涂层,利用XRD、SEM、涡流法对涂层进行了相结构、表面形貌、膜厚的分析,并进行了划痕实验、抗热震性能及阻氚性能测试。结果表明:相结构、表面形貌、膜厚受到微弧氧化电流密度、电压、反应时间的影响。其中,电流密度、电压都能改变涂层相结构,较高电流密度将促进Al→Al_2O_3的形成,而较高电压将促进γ-Al_2O_3→α-Al_2O_3的相变。提高电压、反应时间,涂层表面放电孔洞将变大从而影响表面质量;最佳电流密度为9 A/dm~2,此时表面质量较好。通过性能测试及综合分析,最佳工艺参数为6 A/dm~2、300 V、30 min,膜基结合力、抗热震较好,能使316L不锈钢的氚渗透率降低3个数量级。     

掺杂Ni、Al对YSZ电泳沉积涂层抗氧化和腐蚀性能的影响（英文）

使用电泳沉积和真空烧结技术在Inconel 600合金基体上沉积YSZ/(Ni,Al)涂层,研究在1100°C等温氧化过程中涂层的组成、表面裂纹的自愈合性以及涂层在3.5%氯化钠(质量分数)溶液中的电化学腐蚀性能。结果表明,随着氧化时间的延长,涂层表面上的裂纹逐渐愈合。在恒温氧化过程中涂层中的Ni_3Al转化成α-Al_2O_3微粒,α-Al_2O_3微粒能够对涂层表面的裂纹和气孔等缺陷进行密封,从而阻止氧气扩散到涂层内部。极化曲线和阻抗的测定结果表明,涂层在恒温氧化40 h时有较高的自腐蚀和击穿电位,在低频下有更高的阻抗模值,与基体和纯YSZ涂层相比有更低的自腐蚀电流密度。     

铝合金微弧氧化复合工艺制备陶瓷膜的油摩擦特性

为改善7075铝合金微弧氧化陶瓷膜性能,利用恒流-恒压复合工艺制备微弧氧化陶瓷膜。采用涂层厚度仪、显微硬度计测量陶瓷膜厚度、显微硬度;采用扫描电镜(SEM)和X射线衍射仪(XRD)分析陶瓷膜的表面形貌、磨痕形貌和相组成;采用摩擦磨损试验机研究陶瓷膜油摩擦特性。结果表明:在氧化时间为75 min(恒流)-30 min(恒压)时,陶瓷膜平均厚度达到81μm,陶瓷膜致密层硬度达到1648 HV;陶瓷膜主要由α-Al_2O_3和γ-Al_2O_3组成;微弧氧化陶瓷膜微孔结构有利于改善油润滑条件下的耐磨性;在油润滑条件下,摩擦系数和磨损量随着转速的增大而变大。     

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.     

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.