Effects of Ti<Subscript>0.5</Subscript>Al<Subscript>0.5</Subscript>N coatings on the protecting against oxidation for titanium alloys

Ti0.5Al0.5N coatings were deposited on TC11(Ti-6.5Al-3.5Mo-1.5Zr-0.3Si) and silicon substrates using a cathode arc ion-plating system.The microstructure, composition, phase structure, and oxidation-resistance of the alloys and nitride coatings were investigated by scanning electron microscopy, X-ray diffraction, transmission electron microscopy, Auger electron spectroscopy, and thermal analyzer.The results show that the oxidation resistance of the titanium alloy is relatively limited;the compound structures...     

Ti_(0.44)Al_(0.56)N和Cr_(0.42)Al_(0.58)N涂层的结构与热性能研究

TiAlN和CrAlN涂层是目前切削刀具应用最为广泛的涂层材料。本研究借助阴极弧蒸发技术在低合金钢、钨片和Al2O3刚玉片上制备了Al含量接近的Ti_(0.44)Al_(0.56)N和Cr_(0.42)Al_(0.58)N涂层,采用扫描量热仪(DSC)、扫描电子显微镜(SEM)、X射线能量色散谱仪(EDX)、X射线衍射仪(XRD)和纳米压痕仪对比研究其结构、力学性能、热稳定性及抗氧化性能。结果表明:Ti_(0.44)Al_(0.56)N和Cr_(0.42)Al_(0.58)N涂层均为单相面心立方结构,其硬度分别为30.1±0.4 GPa和30.2±0.7 GPa;Ti_(0.44)Al_(0.56)N涂层在退火过程中会产生时效硬化效应而呈现更好的热稳定性,900℃时为32.4±0.7 GPa;在1 100℃退火后,Ti_(0.44)Al_(0.56)N和Cr_(0.42)Al_(0.58)N涂层的硬度分别降至27.8±0.8 GPa和22.6±0.4 GPa;Cr_(0.42)Al_(0.58)N涂层则具有更优异的抗氧化性能,Cr_(0.42)Al_(0.58)N涂层在1 000℃氧化10 h后,氧化层的厚度仅为0.17μm,而Ti_(0.44)Al_(0.56)N涂层在900℃氧化10 h后已完全氧化。     

High-temperature oxidation of titanium silicide coatings on titanium

Coatings of Ti ₅Si₃ on titanium have been prepared by means of decomposition of silane SiH₄ on heated titanium ribbons. Oxidation of the coated titanium specimens was much slower than that of the noncoated ones. Gravimetric and morphological experiments allowed to propose a mechanism describing the oxidation process.     

Isothermal and cyclic oxidation resistance of boron-modified and germanium-doped silicide coatings for titanium alloys

Since titanium alloys with an adequate balance of mechanical properties and high-temperature oxidation resistance have not been developed, protective coatings are required. In our previous paper, B-modified and Ge-doped silicide diffusion coatings grown on CP Ti, Ti–24Al–11Nb, Ti–22Al–27Nb, and Ti–20Al–22Nb by the halide-activated, pack-cementation method were described. In this study, isothermal and cyclic oxidation were used to evaluate the oxidation performance of these coatings in comparison to uncoated substrates. The rate-controlling mechanism for isothermal oxidation at high temperature was solid-state diffusion through a SiO₂ scale, while the mechanism for low-temperature oxidation involved grain-boundary diffusion through TiO₂. Both isothermal and cyclic oxidation rates for the B-modified and Ge-doped silicide coatings were much slower than for pure TiSi₂. Oxygen contamination was not detected by microhardness measurements in the coated substrates after 200 oxidation cycles at 500–1000°C for the Ti–Al–Nb alloys, or at 500–875°C for CP Ti. The excellent oxidation resistance for the optimum coating compositions is discussed.     

LaNi4.7Al0.3和MlNi4.5Al0.5合金在H2-CO系统中贮氢性能下降的研究

研究了贮氢合金LaNi4.7Al0 .3和MlNi4.5Al0 .5在纯氢 ( 99.999% )及氢中含CO气体杂质条件下的 p c t特性及循环性能。结果表明 ,合金经CO毒化后 ,平台压升高 ,平台倾斜加剧 ,平台宽度缩小 ,饱和吸氢量减小。毒化后两种贮氢合金的循环性能衰退 ,而且随着循环次数的增加吸氢量减少 ,增加CO的浓度 ,吸氢量减少更加明显。合金贮氢性能下降的原因可能是由于表面生成了氧化物及新相 ,阻止了氢的吸附与扩散。     

Glass–ceramic coatings on titanium alloys for high temperature oxidation protection: Oxidation kinetics and microstructure

A glass–ceramic coating is applied on Ti–6Al–4V alloy for oxidation protection at 800 °C. Its dynamic oxidation and microstructure evolution are investigated. The titanium alloy substrate is effectively protected by the glass–ceramic coating, of which the oxidation develops at constant rate. The linear relationship of oxidation is deduced dm/dt = Dρ(C₁ − C₂)/(bC′), and the diffusion coefficient of oxygen at 800 °C in glass is obtained. Oxygen diffusion through glass coating is the controlling step. After the initial firing, silicide interlayer forms between the glass coating and titanium alloy substrate, where the ratio of Ti/Si decreases after oxidation due to Si diffusion and Ti consumption.     

Characterization of microarc oxidation coatings on pure titanium

The morphology, composition, and phase structure of the oxide coatings produced on the surface of pure titanium by alternating-current microarc discharge in aluminate solution were investigated by X-ray diffraction and scanning electron microscopy. The profiles of the hardness H and the elastic modulus E in the coatings were determined using a nanoindenta-tion method. The concentration distributions of Ti, Al, and O in the coating show that this coating over 30 μm thick contains two layers: an outer layer and an inner layer. The oxide coating is mainly composed of TiO2 rutile and Al2TiO5 compounds. During oxidation, the temperature in the microarc discharge channel was very high to make the local coating molten. From the surface to the interior of the coating, H and E increase gradually, and then reach maximum values of 9.78 GPa and 176 GPa respectively at a distance of 7μrn from the coating/titanium interface. They are also rather high near the interface.     

钛合金用Ti0.75Al0.25N防护涂层的制备与抗氧化性能

采用真空电弧离子镀技术在TC11钛合金基片上制备Ti0.75 Al0.25 N防护涂层,并用扫描电子显微镜(SEM)、X射线衍射仪(XRD)、俄歇能谱分析仪(AES)、X射线光电子能谱(XPS)等方法研究了涂层在空气中650～800℃范围内的热防护性能.结果表明,在给定的温度范围内,涂层可有效降低合金的氧化增重;XPS分析表明,表层富Al氧化物以α-Al2O3的形式存在;AES深度分析表明,元素的扩散出现台阶状分布,外层富Al、O,内层富Ti、N,高温氧化时,Al的选择性氧化形成致密的Al2O3层可以阻止基体与外界氧介质的通道,这是涂层防护钛合金具有良好高温性能的原因.     

Boron and phosphorus saturation of nickel coatings on titanium alloys

The use of titanium alloys for parts that operate under contact friction conditions is possible if the alloy's tribological characteristics are substantially improved. This paper concerns the investigation of technological, high-temperature, diffusion saturation with boron and phosphorus coatings on titanium alloy surfaces by the chemical precipitation of nickel.Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 2, pp. 13 – 15, February, 1995.     

机械球磨Ti_(50)Al_(50)复合粉的压制特性

研究了机械球磨Ti50 Al50 复合粉的组织与压制特性。结果表明 ,球磨导致粉末硬度增加 ,压制特性变差 ,这是由于球磨使层片结构细化 ,Ti和Al组元晶体缺陷增加和晶粒细化造成的 ;但球磨 3h形成纳米晶复合粉后 ,尤其是在球磨 7.5h开始发生非晶转变后 ,进一步球磨 ,粉末压制特性变化并不明显     

半固态处理对Zr_(60)Cu_(17.5)Al_(7.5)Ni_(10)Ti_5非晶形成能力和力学性能的影响

采用铜模吸铸法将Ti元素添加到Zr65Cu17.5Al7.5Ni10非晶合金中,制备得到直径为3 mm的大块非晶合金。采用X射线衍射(XRD)、扫描电子显微镜(SEM)、示差扫描量热仪(DSC)和微机控制电子式万能试验机等研究半固态处理对Zr60Cu17.5Al7.5Ni10Ti5大块非晶合金的微观组织结构、非晶形成能力、压缩力学性能以及断口形貌的影响。结果表明:半固态处理技术对非晶合金材料的组织结构和力学性能有很大的影响,能够提高非晶合金的强度和塑性;半固态下Zr60Cu17.5Al7.5Ni10Ti5表现出较好的非晶形成能力,表征非晶形成能力的参数Trg为0.618 9,过冷液相区△Tx达到40 K;且当吸铸电压为7 kV时试样的塑性最好,为1.94%,强度为1 487.411 MPa。     

Ti_3Si_(0.6)Al_(0.6)C_(1.98)陶瓷的制备与性能研究

采用原位热压工艺制备了高纯Ti_3Si_0.6Al_0.6C_1.98陶瓷,并测试了性能.以单质的Ti、Si、Al和石墨粉为原料,摩尔比Ti:Si:Al:C=3:0.6:0.6:1.98,在1500 ℃,30 MPa压力下保温1 h,高纯Ar气保护,制备试样的主要物相为Ti_3Si_0.6Al_0.6C_1.98.制备的Ti_3Si_0.6Al_0.6C_1.98陶瓷的密度为(4.43±0.23) g/cm~3,电阻率为(0.31±0.01)μΩ·m,抗弯强度为(245.46±22.04) MPa,维氏硬度为(2.91±0.32) GPa, 断裂韧性为(5.63±0.39) MPa·m~(1/2).Ti_3Si_0.6Al_0.6C_1.98陶瓷中晶粒以板状晶为主,晶粒层状结构明显,断口形貌显示主要为穿晶断裂,晶粒的分层断裂、微裂纹的偏转桥接及滑移使材料具有独特的压痕特征.     

High-temperature electrochemical performance and phase composition of Ti_(0.7) Zr_(0.5) V_(0.2) Mn_(1.8-x)Ni_x hydrogen storage electrode alloys

1　ＩＮＴＲＯＤＵＣＴＩＯＮＴｈｅｒａｐｉｄｄｅｖｅｌｏｐｍｅｎｔｏｆｅｌｅｃｔｒｉｃｖｅｈｉｃｌｅｓｉｓｉｎ ｅｖｉｔａｂｌｅｂｅｃａｕｓｅｏｆｌｅｓｓｅｎｖｉｒｏｎｍｅｎｔａｌ ｐｏｌｌｕｔｉｏｎ .Ｎｏｗ ,ｏｎｅｏｆＲ＆ＤｄｉｒｅｃｔｉｏｎｓｉｓｆｏｃｕｓｅｄｏｎｔｈｅＥＶｉｎＵＳＡ ,Ｊａｐａｎ ,Ｃａｎａｄａｅｔｃｔｏｓａｔｉｓｆｙｔｈｅｒｅｑｕｉｒｅｍｅｎｔｏｆｔｈｅｒａｐｉｄｄｅｖｅｌｏｐｍｅｎｔｏｆｔｒａｎｓｐｏｒｔａｔｉｏｎ ,ｅｎｅｒｇｙａｎｄｅｎｖｉｒｏｎｍｅｎｔ .Ｆｕｅｌｃｅｌｌ[1,…     

Al67Mn8Ti25合金的解理裂纹

利用Ｓｔｒｏｈ 位错塞积模型解释了Ｌ１２ 结构Ａｌ６７ Ｍｎ８Ｔｉ２５ 合金室温解理裂纹的萌生。计算表明,位错塞积优先在与滑移面成３５ ．３°方向诱发微裂纹, 导致解理断裂。经室温弯曲断口解理面取向的电子背散射衍射（ＥＢＳＤ） 测试结果验证表明,Ｌ１２ 结构Ａｌ６７ Ｍｎ８Ｔｉ２５ 合金室温解理断裂裂纹优先在｛１１０｝ 晶面萌生     

Research progress of laser cladding self-fluxing alloy coatings on titanium alloys

Laser cladding is a new surface modification technology,and is widely used for fabricating wear and corrosion resistant composites coatings. Self-fluxing alloys have many advantages,such as excellent properties of deoxidizing and slagging,high wear resistance,low melting point and easy cladding,and are often used in laser cladding to improve wear and corrosion resistance of titanium and its alloys. In this paper,the recent development of Ni-based and Co-based self-fluxing alloy coatings which includes the influence of rare earth and ceramic particles in coatings are summarized. Besides,the effects of processing parameters,such as laser power and scanning speed,on coatings are reviewed. Finally,the trend of development in the future is forecasted.     

Preparation of ultraviolet-cured nanocomposite coatings for protecting against corrosion of metal substrates

A cycloaliphatic di-epoxy monomer was used to prepare ultraviolet-cured coatings, in the presence of montmorillonites, either commercially available, or modified on purpose (Cloisite Na⁺, Cloisite 30B), dispersed at two different concentrations (5% and 10% w/w).The corrosion resistance of the ultraviolet-cured films coated on a metal substrate was investigated with electrochemical techniques and compared to the behaviour of the neat ultraviolet-cured epoxy resin films. The coatings showed different stability as revealed by the measurements of the barrier properties depending on the type of nanoclay used.Changing the modifier employed the coatings exhibited intercalated or exfoliated morphologies, as assessed by electron microscopy analysis and confirmed by X-ray diffraction results; the prevention of corrosion was proved dependent on the morphology.     

Exchange bias on polycrystalline BiFeO_3/Co_2Fe(Al_(0.5)Si_(0.5)) heterostructures

Polycrystalline antiferromagnetic BiFeO_3(BFO)thin films were grown on Si/Si O_2/Ti/Pt(111) substrates by pulsed laser deposition and then ferromagnetic films Co_2Fe(Al_(0.5)Si_(0.5))(CFAS) by magnetron sputtering. After fabrication, the films were vacuum-annealed under a 0.1-T magnetic field at different temperatures from 150 to 500 °C.The exchange bias field can be tuned by the annealing temperature for the heterostructures, and the electric domain size can be controlled by the crystal grain size. A large exchange bias of about 5*10~(-3)T is observed in one of the samples. It can be speculated that the crystal grain sizes are the key element in determining the exchange bias and coercivity of the films annealed at the temperature of higher than Neel temperature(T N) of BFO. Furthermore, it is possible to extend spin theories from single-crystal BFO system to polycrystalline BFO system.     

深过冷Al_(46.2)Fe_(36.6)Ti_(17.2)包共晶合金的快速凝固及组织演变

采用落管无容器处理技术实现了Al_(46.2)Fe_(36.6)Ti_(17.2)三元包共晶合金的深过冷与快速凝固,获得直径为130~1 150μm的合金粒子,其过冷度范围为202~30 K。研究发现,在自由落体条件下,合金熔体在快速凝固过程中呈现显著的溶质截留效应,包共晶转变进行得不彻底,凝固组织中包含Fe_2Ti相、Fe Al相和τ_2相,其中Fe_2Ti相为初生相,组织呈现枝晶形貌,Fe Al相和τ_2相形成层片状包共晶组织。随着液滴直径的减小,冷却速率增加,过冷度增大,凝固组织中初生Fe_2Ti相的形貌由粗大枝晶逐渐变为细碎枝晶,一次枝晶轴长度与粒子直径呈线性减小关系;包共晶组织由长条状层片变为球状胞,并且层片间距呈指数型减小。     

Formation of micro-arc oxidation coatings on AZ91HP magnesium alloys

In a neutral solution, coating formation by micro-arc oxidation (MAO) on AZ91HP magnesium alloy was studied. The process involved the substrate dissolution and coating development. During the first 5 s, the sample mass decreased, indicating substrate dissolution dominating the process. After 5 s, the sample mass began to increase and the coating development began to predominate the process. The coating was firstly nucleated on α phase and sparks initially appeared mainly on the edges of the sample. With treating proceeded, the coating was becoming uniform; meanwhile, microscopic pores of anodic coatings increased in size and decreased in number.