TC4合金氩弧熔覆Ni60+B4C复合涂层组织及耐磨性

利用氩弧熔覆技术在TC4合金表面成功制备出TiC、TiB、TiB2增强Ti基复合涂层.利用SEM、XRD和EDS分析了熔覆涂层的显微组织;利用显微硬度仪测试了复合涂层的显微硬度;利用摩擦磨损试验机测试了涂层在室温干滑动磨损条件下的耐磨性能.结果表明:氩弧熔覆涂层组织均匀致密,熔覆层与基体呈冶金结合,TC4合金表面有颗粒状TiC、粗大棒状相TiB2、细小棒状相TiB生成;复合涂层明显改善了TC4合金的表面硬度,涂层的最高显微硬度可达1300 HV0.2;复合涂层在室温干滑动磨损试验条件下具有优异的耐磨性,磨损机制主要是魔力磨损,其耐磨性较TC4合金基体提高近10倍.     

原位自生TiC-TiB2增强Fe基复合涂层的凝固特性及形成机理

以Ti、B4C和Fe粉为原料,利用氩弧熔敷技术在Q235钢基体表面制备出原位自生TiC-TiB2增强Fe基复合涂层.利用扫描电镜(SEM)、X射线衍射仪(XRD)对涂层的显微组织进行了分析.并分析了TiC和TiB2颗粒的形成机理和氩弧熔池的凝固特性.实验结果表明:熔敷层组织为TiC和TiB2弥散分布在α-Fe中,熔敷层与基体呈冶金结合,无裂纹、气孔等缺陷;涂层中TiC和TiB2的体积分数约为68%.形成机理主要是以固态扩散机制为主,TiC以小颗粒状和花瓣状先析出,后析出的TiB2多以六边形、短棒状存在,TiB2的组织比较粗大,TiC颗粒比较细小,TiB2的含量大于TiC含量.     

等离子熔敷TiC/γ-(Fe,Ni)复合涂层组织与耐磨性

为了提高奥氏体不锈钢的耐磨性能,扩大其应用范围,以Ti-C-Fe-Ni混合合金粉末为原料,利用等离子熔敷技术在1Cr18Ni9Ti奥氏体不锈钢表面原位合成了TiC增强耐磨复合涂层。分析了涂层的显微组织结构,测试了涂层沿层深方向的硬度分布,评价了涂层在室温干滑动磨损试验条件下的摩擦磨损性能,结果表明:等离子熔敷TiC金属陶瓷增强复合涂层显微组织细小均匀,由花瓣状和少量颗粒状TiC初生相均匀分布在TiC/γ-(Fe,Ni)共晶基体上组成,涂层与不锈钢基材之间形成了完全冶金结合,涂层平均显微硬度约790 HV,涂层在室温干滑动磨损试验条件下表现出良好的耐磨性及较低的摩擦系数。     

氩弧熔敷原位自生TiCp/Ni60A复合材料组织和耐磨性

利用氩弧熔敷技术在16Mn钢表面原位合成TiC增强Ni基复合材料耐磨涂层.采用XRD、SEM等手段分析涂层的组织,测试涂层的室温干滑动磨损性能.结果表明:其室温干滑动磨损机制为显微切削磨损,熔敷层与基体呈冶金结合,TiC颗粒均弥散分布于熔敷层中.涂层有较高的硬度,在室温干滑动磨损试验条件下具有优异的耐磨性.     

ZL104合金氩弧熔敷原位合成TiCp/Al基复合涂层组织及耐磨性

以Al粉、Ti粉和C粉为原料,利用氩弧熔敷技术,在ZL104合金表面原位合成了TiC增强Al基复合材料层,借助扫描电镜、X射线衍射仪对复合涂层的组织进行了分析;利用显微硬度计、摩擦磨损试验机对复合涂层性能进行了测试。结果表明,氩弧熔敷过程中可以充分反应合成TiC颗粒;TiC颗粒呈球状分布,颗粒尺寸约为1.5μm,均弥散分布于熔敷层中。熔敷层与基体呈冶金结合,无裂纹、气孔等缺陷;复合涂层的显微硬度可达660 HV0.2,涂层耐磨性较基体提高近7倍。     

稀土对氩弧熔覆复合涂层组织和性能的影响

以Ti,B4C,Y2O3和Ni60A粉末为原料,利用氩弧熔覆技术在Q235钢基材表面成功制备出镍基增强相复合涂层,运用 XRD,SEM等分析手段研究了复合涂层的显微组织,利用显微硬度仪测试了复合涂层的显微硬度,并用磨损试验机分析了其在室温干滑动磨损条件下的耐磨性能. 结果表明,复合涂层与基体界面无气孔、裂纹,呈冶金结合. 复合涂层由TiC,TiB2,Cr23C6和γ-Ni组成. 稀土加入改变了TiC和TiB2的长大形态,呈颗粒状均匀、细小的分布在熔覆涂层中. 显微硬度和耐磨性测试结果表明,稀土加入后提高其显微硬度和磨损性能.     

钛合金表面氩弧熔覆TiC增强复合涂层组织与性能分析

把石墨粉末预涂在钛合金表面上,利用氩弧熔覆技术成功制备出原位自生TiC增强的金属基复合涂层。利用扫描电镜、X射线衍射仪和能谱仪分析了熔覆涂层的显微组织,探讨了增强相TiC的生成机制;利用显微硬度仪测试了复合涂层的显微硬度并用磨损试验机考察了其在室温干滑动磨损条件下的耐磨性能。结果表明,氩弧熔覆涂层组织均匀致密,原位自生TiC呈树枝晶和细碎的条状均匀地分布于整个涂层中;由TiC增强的复合涂层明显地改善了钛合金的表面硬度．平均硬度约为700HV0．2且沿层深方向呈梯度分布;涂层在室温干滑动磨损条件下的耐磨性明显优于基体,约为钛合金的10．5倍．     

氩弧熔覆原位自生TiC-TiB增强铁基复合涂层组织与性能

以碳粉、钛粉、硼粉和铁粉末为原料,利用氩弧熔覆技术在16Mn钢基材表面成功制备出铁基增强相复合涂层,运用XRD,SEM等分析手段研究了复合涂层的显微组织,利用显微硬度仪测试了复合涂层的显微硬度,并用磨损试验机分析了其在室温干滑动磨损条件下的耐磨性能.结果表明,复合涂层与基体界面无气孔、裂纹,呈冶金结合.复合涂层由TiB,TiC,Fe₂Ti和α-Fe组成.显微硬度和耐磨性测试结果表明,该复合涂层显微维氏硬度高达1000 MPa左右.常温干滑动磨损条件下,复合涂层具有优异的耐磨性.     

氩弧熔覆(WC+SiC)/Ni基复合涂层组织及性能研究

以WC、SiC和Ni60A粉为原料,采用氩弧熔覆技术在Q345钢基体表面制备出WC+γ-Ni5Si2增强Ni基复合涂层.利用扫描电镜(SEM)、X射线衍射仪(XRD)、显微硬度计和滑动磨损试验机对复合涂层的湿微组织、相构成、硬度及耐磨性进行了研究.结果表明:熔覆层相构成为WC、γ-Ni5Si2和γ-Ni,WC以颗粒状析出,由于氩弧熔覆时加热温度高,导致SiC分解,使Si与Ni在高温下形成了γ-Ni5Si2;熔覆层与基体呈冶金结合,无裂纹、气孔等缺陷;涂层最高硬度可达1200 HV0.2,是基体金属的4倍以上;在室温干滑动磨损试验条件下具有优异的耐磨损性能,耐磨性比基体提高了11倍.     

TiB2对Ni基合金激光熔覆层组织与性能的影响

采用5 kW CO2激光器在低碳钢表面熔覆Ni基合金层及TiB2/Ni基合金金属陶瓷涂层,研究了两种涂层的组织、显微硬度以及滑动磨损特性.结果表明,Ni基合金层主要组成相为γ-(Ni,Fe),Cr23C6等,TiB2/Ni基合金复合涂层组成相主要有γ-(Ni,Fe),Ni3B,TiB2和TiC等;Ni基合金层由发达γ-(Ni,Fe)枝晶和其间共晶组织所组成,TiB2/Ni基合金复合涂层典型组织为等轴固溶体以及其间细小共晶组织;TiB2对熔覆层的组织有显著的影响,使熔覆层组织细化,并由树枝晶转变为等轴晶;加入TiB2可显著提高Ni基合金涂层的显微硬度及耐磨性能.     

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.     

新型的治疗阿尔茨海默氏症药物(1-二甲基磷酰基-2,2,2-三氯)-乙基-1-醇烟酸醋对体外神经细胞的作用

目的: 观察本实验室合成的一种治疗阿尔茨海默氏症(AD)的药物(1-二甲基磷酰基-2, 2, 2 -三氯)-乙基^-1-醇烟酸醋(NMF),对体外培养的皮层神经细胞活性的影响以及对海人藻酸(KA)所致的神经损伤的保护作用。方法: 采用体外培养皮层神经元的方法,解剖分离 15 d胚胎小鼠皮层神经细胞, 接种于 96孔板,48 h 后加药并培养 72 h,以 MIT 法 观察 NMF 对小鼠皮层神经细胞活性的影响;同时将接种于 24 孔板的细胞预先给予 NMF,d 3 时加或不加KA处理后,以台盼蓝染色鉴别并计数死、活细胞,可得出细胞的存活率。结果: NMF 明显促进胎鼠皮层神经元活性,其中 NMF1、0. 1、10nmol·L^-1促进神经元活性增殖率分别高达 34.7%、37.4%、36. 7%, NMF 明显促进正常胎鼠皮层神经元存活卒,与对照组比较,10nmol·L^-1 NMF 对皮层神经元的存活率分别提高 39.3%、73.5%。 NMF能显著 对抗 KA 所致的神经元损伤,与 KA 损伤组相比, NMF0.1、10、10nmol·L^-1对损伤皮层神经元的保护率分别为 77.30%、80.10%、84.15%。结论: NMF 明 显促进胎鼠皮层神经元的洁性、提高正常皮层神经元,的存活卒,并能有效地保护KA所致的神经元损伤,提示 NMF 是一种很有潜力的治疗 AD 的药物。     

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.     

Three-Dimensional Growth of Coherent Ferrite in Austenite: A Molecular Dynamics Study

Coherent second phase often exhibits anisotropic morphology with specifi c orientations with respect to both the second and the matrix phases. As a key feature of microstructure, the morphology of the coherent particles is essential for understanding the second-phase strengthening eff ect in various industrial alloys. This letter reports anisotropic growth of coherent ferrite from austenite matrix in pure iron based on molecular dynamics simulation. We found that the ferrite grain tends to grow into an elongated plate-like shape, independent of its initial confi guration. The fi nal shape of the ferrite is closely related to the misfi t between the two phases, with the longest direction and the broad facet of the plate being, respectively, consistent with the best matching direction and the best matching plane calculated via the Burgers vector content(BVC) method. The strain energy calculation in the framework of Eshelby's inclusion theory verifi es that the simulated orientation of the coherent ferrite is energetically favorable. It is anticipated that the BVC method will be applicable in analysis of anisotropic growth and morphology of coherent second phase in other phase transformation systems.     

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.