铂族金属高温固溶强化型合金

讨论了高温固溶强化机制和合金元素对Pt固溶强化效应.介绍了铂族金属和Pt-Rh、Pt-Ir和Pt-Pd-Rh固溶型合金的的高温力学性能.借助不同的强化机制,在Pt-Rh或Pt-Pd-Rh合金中添加少量Ir、Ru、Mo、Au等组元,或微量稀有金属Zr、Hf或稀土金属,可以提高合金的高温强度性质和改善抗蠕变能力.     

双层辉光等离子表面冶金技术

在离子渗氮技术的基础上,发展了双层辉光离子渗金属技术.该技术已成功地将固态合金元素如Ni, Cr, Mo, W, Ti, Al, Nb, Zr以及它们的组合渗入金属材料表面,形成一系列高硬度、耐磨、抗腐蚀合金层.例如在钢铁材料表面形成高速钢和镍基合金;在钛合金表面形成阻燃及耐磨合金等.该技术已获美、英、加等多国专利.本文简要介绍双辉技术的基本原理、主要工艺参数、主要研究结果和应用等.     

钛合金中原子迁移性质的第一原理研究

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。实验研究表明,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。本文采用第一性原理的方法,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。     

合金元素对Zr基大块非晶晶化行为的影响

利用准晶的共轭结构模型构造出了Zr基非晶合金中准晶相的原子结构模型,用递归方法研究了合金元素对非晶晶化过程的影响.结果表明:Zr基非晶合金析出的准晶相存在Zr6Ni,Ni6Zr2种结构,Ni6Zr结构优先析出;合金元素Ag,Pd,Pt,Au固溶于准晶中时,占据Cu,Ni原子的位置,增大近邻原子间的相互作用,这从电子理论角度解释了合金元素Ag,Pd,Pt,Au稳定地促进二十面体准晶(I)相析出的事实.     

The High Temperature Creep Behavior of Dispersion Strengthened Pt5Rh Composite

采用大塑性变形法制备氧化物弥散强化铂铑 (Pt5Rh ODS)复合材料,对材料进行了高温蠕变试验。结果表明,复合材料在高温低应力条件下,表现出的名义应力指数随温度变化较小,名义激活能高于纯Pt和Pt10Rh合金,而且比常规合金材料具有更好的高温蠕变性能。复合材料的高温蠕变性能用晶界反应控制来解释,说明复合材料的蠕变受到扩散蠕变机制控制。复合材料的蠕变断裂行为符合连续蠕变损伤中的内截面损伤模型,蠕变断裂特征为沿晶断裂。     

Creep behaviour of Fe3Al-based alloys in DO3 phase field

A study is made to bring out the effect of alloying with Cr, Ti or Mn on the creep behaviour of Fe₃Al. Impression creep experiments have been carried out in the DO₃ phase field. In all the alloys, power law creep behaviour is observed in the stress range covered. The stress exponent for steady state creep rate and the activation energy for creep indicate that the creep rate is controlled by the dislocation climb process. Among the alloying elements studied, addition of Ti is most effective in improving the creep resistance.     

Microstructure and creep behavior of directionally solidified TiAl-base alloys

Tensile creep tests were conducted on directionally solidified TiAl alloys to discern the effect of alloying and lamellar orientation. A seeding technique was used to align the TiAl/Ti₃Al lamellar structure parallel to the growth direction for alloys of Ti–47Al, Ti–46Al–0.5Si–0.5X (X=Re, W, Mo, and Cr), and Ti–46Al–1.5Mo–0.2C (at.%). Tensile creep tests were performed at 750 °C using applied stresses of 210 and 240 MPa. Aligning the lamellar microstructure greatly enhances the creep resistance which can further be improved by additional alloying.     

Beitrag zum physikalischen und korrosionschemischen Verhalten von IVa-Metallegierungen

The physical and corrosion-chemical behaviour of IVa metal alloys The stability of titanium in respect of non-oxidant acids can be considerably increased by alloying it with Zr, Hf, Nb, Mo or Re. In the case of Zr, Hf, Nb and Ta, a decisive improvement of the corrosion behaviour can only be attained if the At-percentage of these metals in the alloys exceeds 50 pC. In the case of molybdenum, a content from 20 pC upwards has already a markedly passivating effect. But the improvement in corrosion properties must be bought at the price of poorer machinability. A particularly effective alloying metal, even in small quantities, is Rhenium. An excellent corrosion resistance and, at the same time, good machinability can be attained with ternary Ti-Mo-Ta alloys (with Mo + Ta accounting for some 20 At-pC) and with a Ti-12Mo-1Re alloy. The alloying of titanium with Zr, Hf, V, Cr or Mo is apt to cause, in some cases, a considerable deterioration in the scaling resistance of titanium. Improvements can be obtained by using small quantities of Nb, W and particularly Ta. Ti-Ta alloys with Ta contents up to 10 At-pC still have a good scaling resistance at 900° C.     

Einflüsse von Mo,V, Nb,Ti, Zr und deren Karbiden auf die Bindungszustände des Wasserstoffs in Eisen und das Bruchverhalten der Eisenlegieungen

Effects of Mo, V, Nb, Ti, Zr and their carbides on the binding states of hydrogen in iron and the fracture behaviour of the iron alloys Effects of Mo, V, Nb, Ti, Zr and their carbides on hydrogen permeation, diffusion, solubility and its distribution on different binding states in iron and iron based alloys are studied by use of the electrochemical hydrogen permeation technique. The results are analysed and described in terms of the trapping theory. The fracture behaviour of the alloys affected by hydrogen in different binding states are tested under constant elongation rate conditions. No essential specific effects of one of the alloying elements or their carbides are observed. Hydrogen diffusion and solubility, the total hydrogen content as well as the fracture behaviour are affected by the various microstructures of the alloys, thus only indirectly by the alloying elements. Crack initiation and fracture progress depend first of all on the external hydrogen activity and the grain size of the material, not on the total hydrogen content. Fine crystalline iron alloys of higher strength prove to be less sensible to hydrogen damage than coarse grain weak structures.     

First‐principles study on influence of alloying elements on electrochemical stability of cobalt‐base alloys

The paper studies the impact of the metal elements Nb, Ta, Zr, Mo, W, Al, Si, and Y on electrochemical stability of non‐passivated cobalt‐base alloys by evaluating the chemical potential and the electrode potential shift relative to pure cobalt metal using first‐principles calculations. Nb, Ta, and Si are found to make the surface Co atoms more stable on the {0001} surfaces of the corresponding alloys compared to pure Co {0001} surfaces, whereas Al, W, Mo, Y, and Zr make Co atoms less stable. Among all the considered alloying elements, niobium is the most beneficial to the stability enhancement of alloys. Furthermore, the effects of water adsorption on the electrochemical stability are considered. It is found that the surface adsorption properties may be considerably modified by introducing the Nb atoms. Our results indicate that water adsorption destabilizes both the alloy and pure metal surface. However, the Co? Nb alloy surface is still more stable than the pure Co surface in the presence of absorbed water. Our calculation reveals that the electrochemical stability of the Co? Nb alloy is sensitive to water molecular adsorption in comparison with that of the pure Co metal.     

L12型Co3Ti基金属间化合物有序化行为的热力学研究

采用亚晶格模型,辅助以第一性原理总能计算,研究了L12结构的Co3Ti基金属间化合物中元素的占位有序化行为。结果表明,Co3Ti化学计量比合金呈现完全有序化;对于xCo/xTi为3:1的Co72Ti24M4合金,第3合金组元M为Si或Ta时,M与Ti共同占据1a位置,M为Cu、Ni、Pd、Rh、V或W时,M与Co占据3c位置,而当M为Al、Cr、Ge、Mn、Sc或Y时,M在1a和3c位置的占位分数相同,这些元素的占位行为均不受温度影响;而当M为Fe、Hf、Mo、Nb、Ru和Zr的占位情况随温度发生变化。随原子核外层电子的增加,原子占位逐渐倾向于从1a亚晶格转向3c位置。亦预测了xCo/xTi偏离3:1的部分合金的占位分数随合金成分和温度的变化细节,预测结果与文献进行了比较,并澄清了文献上的分歧     

Effect of carbon addition on solidification behavior,phase evolution and creep properties of an intermetallic β-stabilized γ-TiAl based alloy

Improving mechanical properties of advanced intermetallic multi-phase γ-TiAl based alloys, such as the Ti-43.5Al-4Nb-1Mo-0.1B alloy (in at.%), termed TNM alloy, is limited by compositional and microstructural adaptations. A common possibility to further improve strength and creep behavior of such β-solidifying TiAl alloys is e.g. alloying with β-stabilizing substitutional solid solution hardening elements Nb, Mo, Ta, W as well as the addition of interstitial hardening elements C and N which are also carbide and nitride forming elements. Carbon is known to be a strong α-stabilizer and, therefore, alloying with C is accompanied by a change of phase evolution. The preservation of the solidification pathway via the β-phase, which is needed to obtain grain refinement, minimum segregation and an almost texture-free solidification microstructure, in combination with an enhanced content of C, requires a certain amount of β-stabilizing elements, e.g. Mo. In the present study, the solidification pathway, C-solubility and phase evolution of C-containing TNM variants are investigated. Finally, the creep behavior of a refined TNM alloy with 1.5 at.% Mo and 0.5 at.% C is compared with that exhibiting a nominal Ti-43.5Al-4Nb-1Mo-0.1B alloy composition.     

Effects of Microstructure and Processing Methods on Creep Behavior of AZ91 Magnesium Alloy

This review sheds light on the creep properties of AZ91 magnesium alloys with a major emphasis on the influence of microstructure on the creep resistance and underlying creep deformation mechanism based on stress exponent and activation energy. Effects of processing routes such as steel mold casting, die casting, and thixoforming are considered. Roles of a wide range of additional alloying elements such as Si, Sb, Bi, Ca, Sn, REs, and combined addition of them on the microstructure modification were investigated. The reaction between these elements and the Mg or Al in the matrix develops some thermally stable intermetallic phases which improves the creep resistance at elevated temperatures, however does not influence the creep mechanism.     

Electrode materials for electrospark alloying of machine parts

The conditions of producing tungsten alloys with chromium and molybdenum by thermal reduction methods of a scheelite concentrate with the additions of oxides of alloying elements are studied. The application of W–Cr and W–Cr–Mo alloys for electrospark alloying of the surface of machine parts increases the wear resistance of the parts 1.5–2 times.     

基于d电子理论的轻质Nb-Ti高温合金设计

分析了d电子理论在铌基合金中的适用性,改进了Md参数并进行了验证,对轻质铌钛合金系统进行了设计计算。结果表明:固溶强化铌基合金最为有效的元素主要包括W、Mo、Zr、Hf、Ta,铌基合金中加入相同原子分数的W元素的强化效果优于Mo元素;铌基合金中Ti元素的含量增多,会降低合金的高温强度;综合考虑合金密度、高温强度、抗氧化性等因素,通过d电子理论设计出轻质铌钛合金的最优参考组分为(质量分数,%):65.95Nb-17Ti-3Al-4Cr-5V-2W-1.5Mo-1.5Hf-0.05C。     

合金元素对新型Co-Al-W合金热腐蚀行为的影响

研究了由γ'-Co₃(Al,W)相沉淀强化的新型钴基Co-Al-W 高温合金在800℃、75% Na₂SO₄+25% NaCl熔盐中的热腐蚀动力学及合金元素Mo、Nb、Ta和Ti对合金热腐蚀行为的影响。研究发现,2Mo、2Nb、 2Ta和2Ti合金比9.8W合金具有更好的抗热腐蚀能力,Mo和Ti对提高合金耐热腐蚀能力的效果比Ta和Nb显著。加入合金元素的合金热腐蚀膜由三层组成,即主要由Co氧化物CoO和Co₃O₄组成的腐蚀膜外层,由合金元素、Al、 Co及W复杂氧化物组成的中间过渡层和由Al、Co氧化物组成的腐蚀膜内层。随着腐蚀时间的增加,中间过渡层厚度逐渐增加,热腐蚀膜内、外层厚度变化不大,但内层致密性逐渐增加。     

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.     

合金元素对烧结Nd-Fe-B磁体磁性能的影响

述了两类合金元素(代换元素：Co，Dy或Tb与掺杂元素：M1(低熔点元素)：Cu，Al，Ga，Sn，Ge，Zn等与M2(高熔点元素)：Nb，Mo，W，Zr，Ti，V，Cr等)的添加对烧结Nd-Fe-B永磁合金的显微结构和磁性能的影响。综述了两种合金化方式(传统合金化方式：在熔炼前加入合金元素；晶间合金化方式：在球磨或气流磨前加入合金元素)对烧结Nd-Fe-B磁体显微结构和磁性能的不同影响；最后指出晶间合金化复合添加方式是一种很有前景的生产高性能Nd-Fe-B磁体的方法。     

Partition behavior of alloying elements and phase transformation temperatures in Co–Al–W-base quaternary systems

The phase equilibria among γ (A1), γ′ (L1₂), χ (D0₁₉), β (B2) and μ (D8₅) phases and the γ′ solvus and γ solidus temperatures were investigated in the Co–Al–W-based quaternary systems with alloying elements of Ti, V, Nb, Ta, Cr, Mo, Mn, Fe, Ni, Si, Zr, Hf, Ru and Ir by electron probe microanalysis (EPMA) using multiphase alloys and by differential scanning calorimetry (DSC). It was found that Ta, Nb, Ti, V, Mo and W are partitioned to the γ′ or χ phase rather than to the γ phase, while Cr, Mn and Fe tend to be distributed to the γ phase. The correlation between the partition coefficient of alloying elements between γ/γ′, γ/χ and γ/β phases and ab initio formation energy of Co₃X (L1₂), Co₃X (D0₁₉) and CoX (B2) was respectively obtained. It was also found that the γ′ solvus temperature increases by the addition of the γ′ former elements such as Ta, Nb and Ti, which decreases the γ solidus temperature.