等离子体铝离子注入不锈钢提高铝/钢钎焊性能研究

为了实现铝合金和不锈钢的钎焊连接,采用金属等离子体离子源对不锈钢母材进行铝离子注入前处理.注入电压分别为20 kV,30 kV,40 kV,注入剂量为9 × 1017 ions/cm2.评价了BAl88Si钎料在注铝不锈钢表面的润湿铺展能力,对比了有、无铝离子注入前处理的铝钢钎焊强度.结果表明,铝离子注入不锈钢前处理可...     

N / Ti / Al 离子注入 304 不锈钢的耐磨性

目的研究N,Ti,Al离子注入对304不锈钢耐磨性的影响规律,为304不锈钢材料的改良提供参考。方法采用等离子注入技术,在不同剂量下对304不锈钢分别进行N,Ti,Al离子注入,对离子注入后的试样进行表面微观形貌观测、表面硬度测试、摩擦磨损性能测试,并与304不锈钢基材进行对比。结果 304不锈钢经3种离子注入后,均能获得平整、致密,没有裂纹,具有一定光洁度的表面组织,但是注入剂量增大会引起表面起泡现象,形成多孔形貌,光洁度降低。此外,3种离子注入均能提高304不锈钢的表面硬度,且高剂量注入试样的硬度比低剂量注入试样更高,相较而言,N离子注入使表面硬度的提高更明显。相比未注入基材,注N与注Ti表面层的摩擦系数均变小,注Al表面层的摩擦系数反而变大,但磨损量都明显降低。高剂量注N、注Al试样的耐磨性均高于低剂量注入试样,而高剂量注Ti试样的耐磨性低于低剂量注入试样,但仍好于注N、注Al试样。结论在相同实验条件与注入工艺下,N离子注入对表面硬度提高最显著(剂量为5.0×1017ions/cm2),约提高41%;Ti离子注入对耐磨性提高最显著(剂量为3.0×1017ions/cm2),约提高6倍。     

离子注入304不锈钢表面耐腐蚀性的研究

采用先进的等离子注入技术,对304不锈钢分别进行N、Ti、Al离子注入,对比研究了304不锈钢注入不同种离子后的表面耐腐蚀性。研究了离子注入后各试样的表面微观形貌、物相成分和电化学腐蚀性。结果表明:离子注入304不锈钢的表面组织平整、致密。但随着注入剂量的增大,表面光洁度降低,形成多孔形貌;适量的离子注入剂量可获得非晶态注入层,形成单相过饱和固溶体,提高不锈钢的耐腐蚀性;相较两种注入剂量,剂量为5×10~(17)ions/cm~2的各离子注入试样,耐腐蚀性提高;而相同剂量的各离子注入试样,Ti离子注入的效果最好,相比304不锈钢基材,耐腐蚀性能约提高了72%(剂量为5×10~(17) ions/cm~2),其次是注入N,耐腐蚀性约提高了59%(剂量为5×10~(17)ions/cm~2)。     

银离子注入马氏体不锈钢表面改性研究

利用MEVVA源强流离子注入机将银离子注入到马氏体不锈钢表面,注入能量和注入剂量分别为100keV和(0.1~8)×1017ions/cm2。选用革兰氏阳性金黄色葡萄球菌和革兰氏阴性大肠杆菌研究了银离子注入不锈钢的抗菌性能,电化学法测定了其耐蚀性能,AES分析了不锈钢注入层中主要元素的浓度分布,讨论了注入剂量与不锈钢抗菌性能及耐蚀性能的关系。研究表明:随银离子注入剂量的增加,银在注入层中的峰值浓度变化不大,但分布深度增加,马氏体不锈钢抗菌性能显著提高。在100keV注入能量、8×1017ions/cm2注入剂量条件下,银离子注入马氏体不锈钢后可以使其具有最佳的抗菌性能,但耐蚀性能略有下降。     

N~+剂量对304不锈钢离子注入改性层组织和性能的影响

在350℃研究了N~+剂量(3.0×10~(17)~12.0×10~(17) ions/cm~2)对304不锈钢离子注N的影响。利用扫描电镜、维氏显微硬度、X射线衍射仪和万能摩擦试验机对N~+注入层的硬度、相结构和耐磨性进行分析,并对微观机理进行分析。结果表明:经过不同N~+剂量后,钢表面生成了γN相,其表面光洁度、硬度和耐磨性均有所提高。在相同工艺条件下,注N~+剂量为9.0×10~(17) icons/cm~2时,304不锈钢的硬度可达369 HV0.025,与基材相比提高了61%,耐磨性相比基体也显著提升。     

表面机械处理及扩散退火对复合板性能的影响

通过对轧制前表面进行不同处理和轧制后进行不同热处理工艺生产出的不锈钢/铝/不锈钢三层复合板材试样进行微观形貌观测和拉伸试验,探讨了表面处理及热处理工艺对其复合界面结合强度的影响.结果表明,经表面处理轧制后,在400 ℃×1.5 h的扩散退火工艺条件下,复合板综合性能最佳.     

真空退火对Ti6Al4V合金离子注氧层表面形貌和结构的影响

采用等离子体基氧离子注入技术对Ti6Al4V合金进行表面处理.注入电压选取- 50 kV,注入剂量为4.5×1017 ions/cm2.氧离子注入后对注入样品进行不同温度的真空退火处理.真空退火后,样品表面形貌发生显著变化.随着退火温度增加,先后出现点状、条状缺陷和浅白色块状区.500℃真空退火后样品表面粗糙度变化不大,600℃真空退火后样品表面粗糙度急剧增加.真空退火导致注氧层中氧流失,并且不能在注氧层中析出结晶相.     

Ag和Ta离子双注入Ti6Al4V合金表面改性

采用先注入1×1017ion/cm2Ag离子,注入能量为64.2keV;后注入1.5×1017ion/cm2Ta离子,注入能量为146.5keV对Ti6Al4V合金进行离子双注入表面改性。采用X射线衍射分析离子双注入前后Ti6Al4V合金表面的物相;利用X射线光电子能谱研究离子双注入前后Ti6Al4V合金表面元素化合态以及离子双注入Ti6Al4V合金表面元素浓度沿深度方向的分布。结果表明,离子双注入前后Ti6Al4V合金表面都被氧化了,离子注入前合金表面存在TiO、Ti2O3和Al2O3,离子双注入后Ti6Al4V合金表面有TiO2、Ta2O5、TaOx和AgO2新相生成,且在表面还存在少量V2O5和Al2O3。离子双注入合金表面生成的氧化物层形成了扩散阻挡层,阻挡铝离子和钒离子向外扩散,从而减少Ti6Al4V合金表面铝离子和钒离子的释放量。     

加热处理的SiC-C涂层注H~+前后表面形貌及其Si分布的研究

为了提高放射性废物包装用的不锈钢材料的阻氚性能, 采用离子束混合技术在不锈钢表面沉积低Z材料的SiC-C涂层, 对50%SiC-C涂层进行不同条件的加热处理以及随后进行的剂量为1×1018/cm2H+的注入,研究涂层微观结构的变化,该研究为涂层的实际使用提供科学依据.研究结果表明:离子束混合沉积在不锈钢基体上的50%SiC-C涂层经加热处理后会发生涂层元素的扩散迁移. 随着加热温度的提高,发生颗粒凝聚晶化现象; 氢离子注入会产生非晶化效应,同时导致涂层元素Si向表面及界面的增强迁移.     

磁控溅射铝镀层组织对316L不锈钢阳极氧化微孔形成的影响

采用非平衡磁控溅射方法在316L不锈钢表面制备了不同形态与组织结构的铝膜,以该铝膜为模板,通过阳极氧化的方法,在316L不锈钢基体上制备了微孔.研究了铝膜的组织结构对不锈钢表面微孔形成的影响,并分析了基体上微孔的形成机制.结果表明,铝膜结构对微孔制备存在显著影响.当镀铝层晶粒细小、结构致密时,经过阳极氧化后,基体表面上能形成适于承载缓释药物的密度大、孔径小、形状规则的微孔;当镀铝层组织疏松多孔时,在基体表面生成的孔形状不规则,孔径大、密度小.     

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.     

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.