牙科用钛合金研究现状

本文综述了国内外牙科用钛合金发展过程及应用现状；介绍了现有牙科用钛合金弹性模量、抗拉强度、压缩强度、延伸率等力学性能，卤素元素对钛合金腐蚀的影响，不同材质与钛合金在口腔环境中电偶腐蚀，口腔环境中钛合金的微生物腐蚀，牙科钛合金表面特性特别是表面粗糙度对水基液体润湿性影响，设计新型牙科用钛合金时推荐使用的合金元素种类及计算设计采用的d-电子合金设计法等方面研究成果，并指出了目前存在的问题及努力的方向。     

钛及其合金在流动海水中的腐蚀及对其他金属材料的电偶腐蚀作用

本文通过流动海水腐蚀实验和静止海水中的电偶腐蚀实验查明钛及其合金在静止和流动海水中均具有极优良的耐蚀性能,直到36 m/s流速才有可察觉的腐蚀率.钛及其合金可用于现代技术所面临的各种流速的海水中,但钛及其合金在与其它金属材料偶合使用时,会对其它金属材料产生明显的电偶腐蚀作用,在工程应用中必须予以考虑和解决.     

钛及其合金

本文研究了纯钛的物理性能及腐蚀性能。例举了工业纯钛的机械性能。详细地研究了钛及其合金在航空和化学工业以及在海水等工作制件的应用范围并对这种金属的前景作了讨论。对钛合金的焊接,钎焊和非焊接的连接同样也进行了讨论。援引了合金压力     

牙科用钛铜合金的磨削性能和耐磨性能

由于钛具有优异的生物相容性,其在医药和牙科中的应用呈增长的趋势.不过,作为牙科应用时,纯钛的某些性能还存在不足.添加适当的合金元素可以弥补这些缺点,并保持纯钛优异的生物相容性.对于牙科尤其有意义的是磨削性能和耐磨性能,而纯钛这方面较弱.除此之外,合金必须有足够的腐蚀抗力以承受口腔环境侵蚀.     

牙科用钛铜合金的磨削性的磨削性能磨性能

由于钛具有优异的生物相容性，其在医药和牙科中的应用呈增长的趋势。不过，作为牙科应用时。纯钛的某些性能还存在不足。添加适当的合金元素可以弥补这些缺点，并保持纯钛优异的生物相容性。对于牙科尤其有意义的是磨削性能和耐磨性能．而纯钛这方面较弱。除此之外，合金必须有足够的腐蚀抗力以承受口腔环境侵蚀。     

钛及钛钯合金在草酸溶液中的腐蚀行为

采用电化学测试和腐蚀浸泡法,并结合扫描电镜(SEM)和X射线衍射(XRD)等分析手段,研究了纯钛及钛钯合金(Ti-0.2Pa)在草酸溶液中的腐蚀行为.结果表明,钛及钛钯合金在草酸溶液中的腐蚀产物为TiH1.5.在试验条件下,钛钯合金的耐蚀性能虽略优于钛,但若延长试验时间,提高草酸溶液的温度或浓度,均会使钛钯合金腐蚀加重...     

Ti对Fe-Cr-Ni系合金抗氧化性能的影响

<正> 寻求适合在煤的气化环境中长期工作的合金材料得到了人们的重视。这个环境的特点是既有高温氧化作用,又有高温硫化腐蚀。在Ni-Cr合金中加入少量钛能抑制硫化,但不锈钢加入钛后在低氧分压下的氧化速率却有所增高。因此,须进一步探究钛的作用。 本工作研究钛对310和801合金抗高温氧化性能的影响,讨论钛的作用机制。     

Ti-75合金在人工唾液中的腐蚀性实验研究

选择生物材料,在考虑该材料的生物相容性的同时,还要测试该材料在应用环境中的腐蚀性.为探讨Ti-75作为口腔修复材料的可能性,进行了腐蚀性研究.实验是在351型电化学腐蚀系统上进行的,以人工唾液为电解质,测试了Ti-75、TC4、TA2三种软材和临床常用的钴铬合金、镍铬合金的腐蚀性能.结果表明,钛材的自腐蚀电位(Ecoor)高于钴铬合金和镍铬合金,而两种钛合金又高于纯钛,因此,从Ecoor值来看,五种材料的耐蚀顺序应为两种钛合金,纯钛.钴铬合金,镍铬合金.从阳极极化曲线看,当电位升到0.23V时,三种钛材的电流基本不再增加,即进入稳态钝化状态.而且电位从0.23V升到1.2V时,仍处于钝化区,未发现过钝化现象.阳极极化     

硫酸盐还原菌腐蚀影响因素及防腐技术的研究进展

微生物对金属材料的腐蚀现象广泛存在于土壤、空气、海洋和油田等环境下,其中硫酸盐还原菌是最重要的一种腐蚀微生物,因此对金属材料硫酸盐还原菌腐蚀现象的深入研究有着重要意义。简单介绍了硫酸盐还原菌的生理特征和腐蚀机理。重点阐述了硫酸盐还原菌对金属材料腐蚀过程的影响因素,包括材料因素(合金的成分、成分含量、组织结构等)、环境因素(Cl-、Fe2+、磁场、温度等)及其他因素(p H、含氧量、CO2、流速等)。详细综述了控制微生物腐蚀的3种方法(物理方法、化学方法和生物方法)及其防腐机理,为防腐蚀工艺提供理论基础,并认为生物技术防腐方式具有较好的发展前景。最后,总结了目前微生物腐蚀研究存在的一些问题,并提出环境因素和力学因素共同作用下的微生物腐蚀机理是未来腐蚀研究发展方向的核心。     

金属表面混合微生物腐蚀及分析方法研究进展

微生物腐蚀研究一直都是金属腐蚀领域关注的热点,微生物种类的不同,对金属材料的腐蚀影响也不尽相同。实际环境中,微生物的复杂性导致单一微生物的腐蚀机理并不能完全解释实际的腐蚀现象,因此混合微生物体系研究成为微生物腐蚀领域新的研究方向。在基于单种微生物对金属的腐蚀行为及其腐蚀机理的研究基础上,综述了两种微生物的混合体系在金属表面对其腐蚀的影响。归纳总结了混合微生物的构成,重点综述了含有SRB、IOB和其他典型微生物的混合体系的作用过程,分析了混合体系中,不同微生物的相互作用(如协同、竞争作用等)对金属腐蚀影响。梳理了目前混合微生物体系研究的实验环境,并针对混合微生物体系在金属表面腐蚀微观的研究,介绍了几种技术,以期能更加直观地显示混合体系中微生物间的作用机制。最后对研究两种微生物混合体系下的金属腐蚀问题提出了建议和发展方向。     

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.     

电化学噪声数据处理方法概述

综述了常见的电化学噪声数据处理方法,介绍了直流趋势剔除、统计分析、快速傅立叶变换(FFT)法计算功率谱密度(PSD)以及小波变换处理电化学噪声信号的基本过程,并阐释了各种数学处理及所得参数的物理意义。