钛合金中原子迁移性质的第一原理计算

钛合金作为一种重要的航空材料,具有比强度高、耐蚀性好等优异性能,并具有一定的高温蠕变抗力。但是在更高温度下,有限的蠕变抗力限制了钛合金的进一步应用。研究表明,钛合金稳态蠕变过程蠕变激活能与合金的表观扩散激活能非常接近,说明原子的扩散与蠕变过程密切相关。采用第一性原理方法,计算了钛合金中常见的杂质及合金原子的迁移能垒。结果表明,对以空位机制扩散的合金原子,其在基面内迁移的能垒从高到低为Al、V、Ti、Sn、Ta、Mo、Nb、Zr,面间原子迁移由难到易为Al、Sn、V、Ti、Ta、Mo、Nb、Zr。以间隙机制迁移的Co、Fe、Ni迁移能垒较低,与实验观测到的这些原子为快扩散原子相符。     

新型TiNbTaZr合金的生物腐蚀性和细胞毒性(英文)

通过真空自耗电弧炉开发一种新型β钛合金Ti35Nb2Ta3Zr,其弹性模量仅为48GPa,探讨该合金的耐腐蚀性能和细胞毒性。在Ringer模拟体液中,通过测量开路电位、极化阻抗谱和极化曲线发现Ti35Nb2Ta3Zr的腐蚀性优于Ti6Al4V和Ti。细胞毒性试验证明Ti35Nb2Ta3Zr的生物相容性与目前临床常用的Ti6Al4V和Ti相当。因此,该新型β钛合金Ti35Nb2Ta3Zr具有良好的耐腐蚀性和生物相容性,未来作为生物材料具有广阔前景。     

低温时效对生物相容β钛合金TiNbSn超弹性行为的影响

近期,一些文献陆续报道了无镍β钛合金的形状记忆效应和超弹性行为的研究结果,这些合金系如Ti—Mo—Al,Ti—Nb—Sn,Ti—Mo—Ga,Ti—Nb—Al,Ti—Nb及Ti—Nb—Zr—Sn。人们希望用其替代TiNi形状记忆合金,以消除TiNi合金作植入件对人体产生的过敏或致癌影响。在上述这些合金中,TiNbSnβ钛合金以其良好的生物相容性和冷加工性能备受人们的青睐。但与TiNi合金类似,TiNbSn合金的马氏体转变温度非常敏感。     

Timetal 5111和Timetal 5111 0.05Pd钛合金

Timetal5111合金是80年代末期由Timet与美国海军共同开发研制的近a型钛合金。合金成分为：Ti－5Al－1Zr－1Sn－1V－0．8Mo－0．1Si。合金的突出特点是良好的断裂韧性及抗应力腐蚀性能，应力腐蚀危险比，该性能指标优于船用钛合金48－OT3（Ti－4AI－0．005B），相当于Ti－6211（Ti－6Al－2Nb－1Ta－0．8Mo）；冲击韧性大约为Ti－6Al－4V的3倍；易焊接，可进行大型材的焊接。该合金强度略低于Ti－6Al－4V，延性略高于Ti－6Al－4V，σb＝750MPa～800MPa，s≥13％，但通过调整氧含量可使强度达到Ti－6Al－4V的水平。目前可生产重…     

钛及钛合金的热处理

钛及钛合金通过程序控制技术和各种热处理工艺可获得不同特性的产品 ,表 1～表4列出了工业纯钛及部分钛合金的热处理工艺。表 1　工业纯钛和部分钛合金的 β相变温度合　金β相变温度℃ ,± 1 5° ,± 2 5°工业纯钛 ,0 2 5%O2 最大 91 0 1 6 75工业纯钛 ,0 4 %O2 最大 94 51 735α或近α合金Ti 5Al 2 5Sn 1 0 50 1 92 5Ti 8Al 1Mo 1V 1 0 4 0 1 90 0Ti 2 5Cu (IMI 2 30 ) 8951 6 45Ti 6Al 2Sn 4Zr 2Mo 9951 82 0Ti 6Al 5Zr 0 5Mo 0 2Si(IMI 6 85) 1 0 2 0 1 870Ti 5 5Al 3 5Sn 3Zr 1Nb 0 3Mo 0 3Si (IMI 82 9) 1 0…     

基于Ti1100合金的微量元素添加对合金抗氧化性能的影响

本文利用固溶体合金中的‘团簇加连接原子’模型解析了典型高温近α-Ti合金Ti1100的成分,其团簇成分式为[Al-(Ti13.7Zr0.3)](Al0.69Sn0.18Mo0.03Si0.12)。在此基础上,采用相似元素替代原则设计了微量元素Hf、Ta和Nb添加的系列合金成分,即 [Al-(Ti13.7Zr0.15Hf0.15)](Al0.69Sn0.18Si0.1(Mo/Ta/Nb)0.03)。对该系列合金进行950 ℃/1 h固溶+560 ℃/6 h时效处理,然后进行组织结构、硬度、抗高温氧化及电化学腐蚀性能测试。研究结果表明,Zr0.15Hf0.15合金与参比合金具有相同片层β转变组织,而在此基础上Ta和Nb的添加会使合金中产生大量等轴α组织;但组织的改变对系列合金的显微硬度影响不大,介于330-370 HV。650 ℃氧化100 h后系列合金均具有较强的抗氧化能力,氧化增重小于1.0 mg/cm2,而在800 ℃氧化100 h后,添加Hf、Ta、Nb元素的合金氧化增重明显低于Ti1100合金,氧化层厚度为25~27 μm,且氧化层致密,其中[Al-(Ti13.7Zr0.15Hf0.15)](Al0.69Sn0.18Si0.1Ta0.015Nb0.015)合金具有最优的抗高温氧化性能,800 ℃/100 h后的氧化增重仅为2.6 mg/cm2。此外,该系列合金在在3.5 %NaCl溶液中也具有较好的耐蚀性。     

新近研制的三种钛合金

钛加工的新方法概括起来主要包括扩散焊、超塑性成型、等温锻造以及粉末固结。虽然并非这几种方法都得到了充分地发展,但与常规的方法相比,每一种都可使成本节约高达50%;并且在某些情况下,也减轻了重量。随着这些制造方法的出现,两种重要的新合金也正在问世。它们分别是适于制作锻件的近β钛合金,Ti—10V—2Fe—3Al;和适于制作板、带材的β钛合金、Ti—15V—3Cr—3Al—3Sn,即 Ti—15—3型合金。此外,一种抗蠕变能力优于其它钛合金的超α合金、Ti—6Al—2Sn—4Zr—2Mo—0.1Si 已用于制造先进的气体涡轮机排气混     

低Nb含量Ti-Mo-Nb-Zr-Sn BCC低弹性模量固溶体合金的成分设计

依据BCC结构中的"团簇加连接原子"模型确定Ti-Mo二元团簇式[MoTi14]Mo1为基础成分式,根据合金化组元Sn、Zr和Nb与基体Ti的混合焓实现其在基础成分式中的组元替换,从而形成多元成分式[(Mo,Sn)(Ti,Zr)14]Nb1。利用铜模吸铸快冷技术制备d 6 mm合金棒状样品,并对其进行950℃保温2 h并水淬。组织结构分析和拉伸力学性能结果表明:低模量Sn、Zr和Nb分别取代基础成分式中高模量的Mo时形成的三元BCCβ-Ti合金结构稳定,且具有较低的弹性模量;当Mo0.5Sn0.5占据团簇心部,Nb作为连接原子,Zr替代部分Ti时形成的低Nb含量的β-Ti合金[(Mo0.5Sn0.5)(Ti13Zr)]Nb1(Ti68.10Mo5.25Sn6.50Zr9.98Nb10.17,质量分数,%)具有最低的弹性模量(为43 GPa),且断裂强度σb为569 MPa,应变ε为5.6%。     

合金元素对β-Ti25Nb合金的结构稳定性与弹性性质的影响

采用密度泛函理论的缀加平面波加局域轨道的第一性原理和超晶胞方法对β结构的Ti75Nb25以及Ti68.75Nb25X6.25(X为Mo,Sn,Ta和Zr)合金的能量、电子结构以及弹性性质进行了理论计算.通过对比这几种合金的结构稳定性和弹性性质,发现Mo和Ta元素既能起到稳定β-Ti25Nb相作用,又能使其弹性常量增加.而Sn 对β结构的稳定性影响较小,Zr却降低了β结构的稳定性,且两者对弹性常数的影响均较小.     

新的医用钛合金的开发

作为医用金属材料,生物适应性优良的钛及钛合金目前最引人注目。要求高强度的人工股关节棒等使用了Ti-6Al-4V(ELI)合金。但是由于析出极微量的V和Al离子,降低了其细胞的适应性,且担心Al离子会引起-型痴呆症。选择细胞适应性好的Zr,Nb,Ta,Pd,Sn作为合金的添加元素。为了提高合金的强度可把Sn,Zr作为主要添加元素;提高耐蚀性添加Ta,Pd;为使α β两相组织具有良好的     

The site occupancies of alloying elements in TiAl and Ti3Al alloys

The site occupancies of V, Cr, Mn, Fe, Ni, Zr, Nb, Mo, Ta, Ga and Sn (1–5 at.%) in TiAl alloys with different compositions, and in Ti₃Al with the compositions of Ti–26 at.%Al–(1–2 at.%)X, were measured by the atom location channelling enhanced microanalysis (ALCHEMI) method. For TiAl alloys, the results show that Zr, Nb and Ta atoms invariably occupy Ti sites, while Fe, Ni, Ga and Sn atoms occupy Al sites, the alloy composition having no significant influence on their site preference. By contrast, the site preference of V, Cr, and Mn changes considerably with alloy composition (the Ti/Al ratio in particular), the probability of these elements substituting for Ti decreasing in the above order. For quaternary Ti–Al–V–Cr alloys, the site occupancies of V and Cr do not show much mutual influence. In general, with increasing atomic number, elements in the same period show increasing tendency to substitute for Al, as is the tendency to substitute for Ti for elements in the same group of the periodic table. For Ti₃Al alloys, Ga and Sn atoms occupy Al sites, while V, Cr, Mn, Zr, Nb, Mo and Ta atoms occupy Ti sites, the site preference of V, Cr, Mn and Mo in TiAl alloys being different from that in Ti₃Al. The experimental results are interpreted in terms of a Bragg–Williams-type model and bond-order data obtained from electronic structure calculation. Qualitative agreement between the model and measurements is reached.     

Corrosion behavior of Ti‐xNb‐13Zr alloys in Ringer's solution

Ti‐6Al‐4V alloy has been widely used in restorative surgery due to its high corrosion resistance and biocompatibility. Nevertheless, some studies showed that V and Al release in the organism might induce cytotoxic effects and neurological disorders, which led to the development of V‐free alloys and both V‐ and Al‐free alloys containing Nb, Zr, Ta, or Mo. Among these alloys, Ti‐13Nb‐13Zr alloy is promising due to its better biomechanical compatibility than Ti‐6Al‐4V. In this work, the corrosion behavior of Ti, Ti‐6Al‐4V, and Ti‐xNb‐13Zr alloys (x = 5, 13, and 20) was evaluated in Ringer's solution (pH 7.5) at 37 °C through open‐circuit potential measurements, potentiodynamic polarization, and electrochemical impedance spectroscopy. Spontaneous passivity was observed for all materials in this medium. Low corrosion current densities (in the order of 10^?7 A/cm²) and high impedance values (in the order of 10⁵ Ωcm² at low frequencies) indicated their high corrosion resistance. EIS results showed that the passivating films were constituted of an outer porous layer (very low resistance) and an inner compact layer (high resistance), the latter providing the corrosion resistance of the materials. There was evidence that the Ti‐xNb‐13Zr alloys were more corrosion resistant than both Ti and Ti‐6Al‐4V in Ringer's solution.     

In vitro corrosion resistance and cytotoxicity of novel TiNbTaZr alloy

A novel β type Ti35Nb2Ta3Zr alloy with low modulus (48 GPa) was fabricated using vacuum consumable arc melting. The corrosion resistance and cytotoxicity of Ti35Nb2Ta3Zr were evaluated. The open circuit potential, electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization methods were used to determine the corrosion resistance. In Ringer's solution, Ti35Nb2Ta3Zr alloy exhibits better corrosion resistance, as compared to that of Ti6Al4V and Ti. The cytotoxicity tests indicate that the biocompatibility of Ti35Nb2Ta3Zr is as good as Ti and Ti6Al4V which are widely used in biomedical fields. Based on corrosion resistance and cytotoxicity, the novel β type Ti35Nb2Ta3Zr alloy can be considered as a potential biomaterial.     

Microstructure and properties of novel quinary multi-principal element alloys with refractory elements

Five equiatomic alloys(Ti Zr Hf VNb, Ti Zr Hf VTa, Ti Zr Nb Mo V, Ti Zr Hf Mo V and Zr Nb Mo Hf V) composed of five elements with high melting temperature, respectively were prepared by arc-melting to develop a novel high temperature alloy. The five alloys exhibit different dendritic and interdendritic morphologies. The Ti Zr Hf VNb, Ti Zr Hf VTa and Ti Zr Nb Mo V alloys formed disordered solid solution phases with body-centered cubic structure, and exhibited high compressive strength and good plasticity. The Ti Zr Hf Mo V and Zr Nb Mo Hf V alloys are composed with Laves phase(Hf Mo2) and disordered solid solution phases with body-centered cubic structure. The Ti Zr Hf Mo V and Zr Nb Mo Hf V alloys are harder and more brittle than the other three alloys due to the existence of hard and brittle Laves phases. At high temperatures, the strength decreases to below 300 MPa for the Ti Zr Hf VNb and Ti Zr Hf Mo V alloys. Solution strengthening is the primary strengthening mechanism of the Ti Zr Hf VNb, Ti Zr Hf VTa and Ti Zr Nb Mo V alloys, and brittle Laves phase is the main cause for the low ductility of the Ti Zr Hf Mo V and Zr Nb Mo Hf V alloys.     

Effect of Yttrium on Microstructure and Properties of High Temperature Alloys

ＩｎｔｒｏｄｕｃｔｉｏｎＩＭＩ８２９ｔｉｔａｎｉｕｍａｌｏｙｉｓａｋｉｎｄｏｆｈｉｇｈｔｅｍｐｅｒａｔｕｒｅｎｅａｒαａｌｏｙ．Ｉｔｓｓｅｒｖｉｃｅｔｅｍｐｅｒａｔｕｒｅｉｓｕｐｔｏ５８０℃．ＩｔｈａｓｂｅｅｎｕｓｅｄｉｎＲＢ２１１５２５Ｅ４ｅｎ...     

Passivity and pitting of corrosion resistant pure metals Ta,Nb, Ti,Zr, Cr and A1 in chloride solutions

The relative passivity and pitting resistance of pure metals Ta, Nb, Ti, Zr, Cr and A1 in chloride solutions were studied through quasi-stationary potentiokinetic anodic polarization technique. Studies were conducted in both non-aqueous methanolic and aqueous chloride solutions containing 0.4% HC1 with either hydrogen or oxygen saturation, in order to determine the role of water and oxygen in the passivity of these metals. Ta and Nb are passive in all the solutions, Zr and Cr require sufficient water to become passive, Ti needs both water and oxygen for stable passivity while A1 dissolves actively in all the solutions. The pitting resistance of the above metals decreases in the order Ta > Nb > Ti > Cr > Zr > Al. These passive metals are prone to pitting in chloride solutions in the absence of sufficient water which is the essential passivating agent.     

Influence of Zr content on microstructure and mechanical properties of implant Ti–35Nb–4Sn–6Mo–xZr alloys

The influence of Zr content on the microstructure and mechanical properties of implant Ti–35Nb–4Sn–6Mo–xZr (x=0, 3, 6, 9, 12, 15; mass fraction) alloys was investigated. It is shown that Ti–35Nb–4Sn–6Mo–xZr alloys appear to have equiaxed single β microstructure after solution treatment at 1023 K. It is found that the grains are refined first and then coarsened with the increase of Zr content. It is also found that Zr element added to titanium alloys has both the solution strengthening and fine-grain strengthening effect, and affects the lattice parameters. With increasing the Zr content of the alloys, the strength increases, the elongation decreases, whereas the elastic modulus firstly increases and then decreases. The mechanical properties of Ti–35Nb–4Sn–6Mo–9Zr alloy are as follows: σ_b=785 MPa, δ=11%, E=68 GPa, which is more suitable for acting as human implant materials compared to the traditional implant Ti–6Al–4V alloy.     

First principles study of site substitution of ternary elements in NiAl

Site substitution of ternary elements in ordered compounds influences the electronic structure and hence the properties of compounds at the continuous level. The electronic structure and binding energy of a number of NiAl-X alloy systems (X=Ti, V, Cr, Mn, Fe, Co, Zr, Nb, Mo, Hf, Ta, W, Si, Ga, or Ge) were calculated using the discrete variational cluster method based on the local density approximation of the density functional theory. The site preference of the ternary additions to NiAl was investigated by employing the Bragg–Williams model to analyse the calculated binding energy. The results show that all the considered ternary elements possess stronger preference to the Al sublattice sites than a Ni atom does. A new method of identifying sublattice substitution of ternary additions in NiAl was proposed by comparison of the binding energies per atom of the ternary and the binary clusters involving the fourth nearest neighbours. The analysis suggests that Fe and Co atoms occupy the Ni sublattice sites, whereas Si, Ga and Ti atoms occupy the Al sublattice sites. The remaining elements may substitute for both sublattices: Mn is most likely to go for the Ni sublattice; V, Cr, Zr, Nb, Mo, Hf, Ta, W and Ge have a larger preference for the Al sublattice, but Cr and W do not show significant preference to any sublattice. The densities of states involving alloying additions of Co, Si and Cr were further investigated to clarify the site preference of the alloying additions.     

NiAl合金缺陷电子结构及能量学研究

本文运用基于密度泛函理论的离散变分法研究了NiAI晶体及其中Al被Ti，Zr，Hf，V，Nb，Ta，Cr，Mo，W置换后的电子结构，给出了密立根集居数，态密度，结合能，差分电荷密度等信息。从微观电子结构角度探讨了合金化元素对NiAI晶体塑性影响的规律。