V/Nb对Ti-45Al-9(V, Nb, Y)合金抗氧化性能的影响

βγ-TiAl合金具有良好的高温变形能力,为TiAl合金的发展开辟了新的途径。成功制备了不同x=V/Nb(x=1,1.5,2,3.5)的βγ-TiAlTi-45Al-9(V,Nb,Y)合金,研究了上述合金在800℃静止空气中的氧化行为。结果表明:当x=1时,Ti-45Al-9(V,Nb,Y)合金中形成条带状、连续致密的Al2O3氧化层,显著提高了合金的抗氧化能力。随着x=V/Nb的增加,Al2O3氧化层厚度变薄,合金的抗氧化能力下降。     

Microstructural control of Ti-Al-Mo-Nb alloy system with respect to variation of B

In the current study, phase stability of Ti-Al-Mo-Nb alloys was investigated, and the effect of B addition was examined for cast alloys. The fabricated cast alloys were mainly composed of α₂ / γ lamellar with a β phase, when they were heat treated at 1100 °C followed by air cooling, the alloy was composed of α2 / γ lamellar with γ+β necklace phase at the colony boundary for the Ti-45Al-3Mo-2Nb-1B alloy, and the colony size was refined to ~ 20 μm. In order to identify the effect of the microstructures on mechanical strength, compressive tests were performed on the fabricated alloys of Ti-45Al-3Mo-2Nb and Ti-45Al-3Mo-2Nb-1B at room temperature and at 800 °C. The microstructural variations and phase stability were discussed in terms of pseudo-binary phase diagram calculated by Pandat software?.     

Microstructures,micro-segregation and solidiifcation path of directionally solidiifed Ti-45Al-5Nb alloy

To investigate the effect of solidification parameters on the solidification path and microstructure evolution of Ti-45Al-5Nb (at.%) aloy,Bridgman-type directional solidiifcation and thermodynamics calculations were performed on the aloy. The microstructures, micro-segregation and solidiifcation path were investigated. The results show that the β phase is the primary phase of the aloy at growth rates of 5-20 μm?s-1 under the temperature gradients of 15-20 K?mm-1, and the primary phase is transformed into an α phase at relatively higher growth rates (V >20 μm?s-1). The mainly S-segregation and β-segregation can be observed in Ti-45Al-5Nb aloy at a growth rate of 10 μm?s-1 under a temperature gradient of 15 K?mm-1. The increase of temperature gradient to 20 K?mm-1 can eliminate β-segregation, but has no obvious effect on S-segregation. The results also show that 5 at.% Nb addition can expand the β phase region, increase the melting point of the aloy and induce the solidiifcation path to become complicated. The equilibrium solidiifcation path of Ti-45Al-5Nb aloy can be described as , in which βR and γR mean the residual β andγ.     

INFLUENCE OF ALLOYING ELEMENTS（Nb，Mo，V） ON MICROSTRUCTURE OF Ti_3Al BASE ALLOYS

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Study of microstructure and mechanical properties of Ti-45Al-(Fe,Nb) (at. %) alloys

In the present work, the microstructure and compression properties of two novel γ(TiAl) based alloys, Ti-45Al-5Fe and Ti-45Al-5Fe-5Nb, have been investigated. Both alloys had a relatively fine as-cast structure generally consisting of the γ(TiAl) and τ₂(Al₂FeTi) phases with a minor amount of the α₂(Ti₃Al) and β(B2) phase. The compression properties of the novel alloys were measured at room and elevated temperatures. The Ti-45Al-5Fe-5Nb alloy showed higher room temperature ductility and similar strength at room and elevated temperatures as well as improved workability at elevated temperatures as compared to β-solidifying γ(TiAl) alloys of last generation (TNM alloys).     

High-Temperature Oxidation Behavior of Ti-22Al-27(Nb, Zr) Alloys

研究了Ti2Al Nb基合金Ti-22Al-(27-x)Nb-x Zr(x=0,1,6,at%)在650~800℃的氧化行为。采用XRD和SEM等测试技术对此温度区间形成的氧化层特征进行了分析。结果表明,相比Ti-22Al-27Nb,含锆合金具有较好的抗氧化性能。Ti-22Al-(27-x)Nb-x Zr合金在650℃氧化100 h,主要氧化产物为Ti O2,而在800℃氧化100 h,Ti O2,Al2O3和Al Nb O4为主要产物,但是在Ti-22Al-21Nb-6Zr合金中还有Zr O2生成。Ti-22Al-26Nb-1Zr合金具有优异抗氧化性能,归因于氧化产物细化形成了致密的氧化层,而Ti-22Al-21Nb-6Zr合金,虽然在800℃也形成了较多Al2O3,但是氧化层中的Zr O2为氧的快速扩散提供通道,进而导致该合金氧化增重明显。     

Design for Ti-Al-V-Mo-Nb alloys for laser additive manufacturing based on a cluster model and on their microstructure and properties

In this study, α+β Ti-Al-V-Mo-Nb alloys with the addition of multiple elements that are suitable for laser additive manufacturing (LAM) were designed according to a Ti-6Al-4V cluster formula. This formula can be expressed as 12[Al-Ti₁₂](AlTi₂)+5[Al-Ti₁₄]((Mo, V, Nb)₂Ti), in which Mo and Nb were added into the alloys partially instead of V to give alloys with nominal compositions of Ti-6.01Al-3.13V-1.43Nb, Ti-5.97Al-2.33V-2.93Mo, and Ti-5.97Al-2.33V-2.20Mo-0.71Nb (wt.%). The microstructures and mechanical properties of the as-deposited and heat-treated samples prepared via LAM were examined. The sizes of the β columnar grains and α laths in the Nb-containing samples are found to be larger than those of the Ti-6Al-4V alloy, whereas Mo- or Mo/Nb-added alloys contain finer grains. It indicates that Nb gives rise to coarsened β columnar grains and α laths, while Mo significantly refines them. Furthermore, the single addition of Nb improves the elongation, whereas the single addition of Mo enhances the strength of the alloys. The simultaneous addition of Mo/Nb significantly improves the comprehensive mechanical properties of the alloys, leading to the best properties with an ultimate tensile strength of 1,070 MPa, a yield strength of 1,004 MPa, an elongation of 9%, and micro-hardness of 355 HV. The fracture modes of all the alloys are ductile-brittle mixed fracture.     

Ti-6Al-4V合金的轧制与组织性能

采用光学显微镜、透射电镜和拉伸试验等手段,研究了多道次两向轧制和单向轧制对不同原始状态(热轧态、水淬态和空冷态)Ti-6Al-4V合金显微组织和力学性能的影响。结果表明,热轧态Ti-6Al-4V合金的组织为片状α相+β相+少量等轴α相,水淬态Ti-6Al-4V合金形成了针状马氏体组织,空冷态Ti-6Al-4V合金形成了网状组织。Ti-6Al-4V合金适宜的两向轧制温度为700 ℃,此时合金中可见颗粒状β相弥散分布在α基体上。两向轧制Ti-6Al-4V合金的抗拉强度和屈服强度从高至低顺序为:水淬态>热轧态>空冷态,且轧向强度要高于横向;相较于单向轧制,两向轧制明显降低了Ti-6Al-4V合金板材拉伸性能的各向异性,且水淬态Ti-6Al-4V合金的轧向和横向强度差异最小,700 ℃轧制Ti-6Al-4V合金的主要细化机制为位错细化。     

Fe和Mo元素对TiAl金属间化合物显微组织和性能的影响(英文)

β相可以提高TiAl金属间化合物的塑性。通过显微组织分析和变形行为的评估研究β稳定性元素Fe和Mo对Ti-45Al-xFe-yMo(x,y=1,2,3,4)合金的影响。结果表明:合金中的B2(β)相随着Fe和Mo元素含量的增加而增多,Mo表现出强的β稳定性。加入3%Fe和2%Mo后,合金的晶粒得到细化,其尺寸达到12-m。由于具有一定量的β相,细化后的Ti-45Al-3Fe-2Mo合金在790℃具有良好的塑性。     

Effect of Nb Content on Solidification Characteristics and Microsegregation in Cast Ti-48Al-xNb Alloys

Microstructural evolution in nonequihbrium solidification of Ti-48Al-xNb alloys with Nb contents ranging from2 to 8 at%has been studied by containerless electromagnetic levitation.Levitated drops of controlled undercooling were quenched onto chill copper substrates and subjected to phase and microstructure analysis.With increasing Nb content,the solidification path changes gradually from hyperperitectic solidification to hypoperitectic solidification and both solidification segregation(S-segregation) and β-solidification gradually increase.A transition from typical hypoperitectic solidification to a sole solidification of the β phase beyond a critical undercooling is revealed for the Ti-48Al-8Nb hypoperitectic alloy.For the Ti-48Al-2Nb alloy,the morphologies of the primary β dendrites are not observed.With increasing undercooling,the coarsening of the lamellar colonies occurs,which can be attributed to the transition of the primary β dendritic morphology.Furthermore,the solute concentration profiles for the final solidification microstructure are obtained to examine the segregation behaviors of alloying elements.With increasing Nb content,the undercooling eliminating S-segregation gradually increases.     

Surface characterization of passive film formed on nitrogen ion implanted Ti-6Al-4V and Ti-6Al-7Nb alloys using SIMS

The aim of this paper is to study the effect of N⁺ ion implantation on corrosion and phase formation on the implanted surfaces of Ti-6Al-4V and Ti-6Al-7Nb alloys. Nitrogen ion was implanted on Ti-6Al-4V and Ti-6Al-7Nb alloys at an energy of 70 and 100 keV, respectively using a 150 keV accelerator at different doses ranging from 5 × 10¹⁵ to 2.5 × 10¹⁷ ions/cm². Electrochemical studies have been carried out in Ringer’s solution in order to determine the optimum dose that can give good corrosion resistance in a simulated body fluid condition. The implanted surfaces of such modified doses were electrochemically passivated at 1.0 V for an hour. Secondary ion mass spectroscopy was used to study and characterize titanium oxide and titanium nitride layers produced on implanted surface and to correlate them with the corrosion resistance. The nature of the passive film of the implanted-passivated specimen was compared with the unimplanted-passivated as well as as-implanted specimens.     

Effect of Nb on oxidation behavior of high Nb containing TiAl alloys

The isothermal oxidation behavior of Ti-45Al-8Nb and Ti-52Al-8Nb alloys at 900 °C in air was investigated. The early oxidation behaviors were studied by using XPS and AES. And the microstructure and the composition of the oxidation scale were studied by using XRD and SEM. The results show that the oxidation behavior of TiAl alloy is significantly improved by Nb addition. Nb substitutes for Ti in TiO₂ as a cation with valence 5, and thus to suppress TiO₂ growth. The (Ti,Nb)O₂-rich layer is a dense and chemically uniform which is more protective than the TiO₂ layer. Nb addition also lowers the critical Al content to form an external alumina. Nb₂Al phase is formed in the metallic matrix at the oxide–metal interface on the high Nb containing TiAl alloys.     

氢对Ti-6Al-4V合金微观组织的影响

采用累计流量法对供应态Ti-6Al-4V合金进行了固态置氢,运用OM、XRD、TEM分析等方法研究了Ti-6Al-4V合金固态置氢后的微观组织状态及演变过程。结果表明:供应态Ti-6Al-4V合金的置氢量低于0.30%(质量分数,下同)时,置氢使得Ti-6Al-4V合金中的α相减少、β相增加;置氢量达到0.30%时,置氢Ti-6Al-4V合金中有δ氢化物(TiH2相)形成;β-Ti(H)共析转变生成α-Ti和δ氢化物时主要以切变方式进行;置氢Ti-6Al-4V合金的相变温度最多下降了180°C,与Ti-6Al-4V合金在置氢过程中的相体积比变化和共析转变有密切关系。     

Influence of Mo content on microstructure and mechanical properties of β-containing TiAl alloy

The influence of Mo content on the microstructure and mechanical properties of the Ti-45Al-5Nb-xMo-0.3Y (x=0.6, 0.8, 1.0, 1.2) alloys was studied using small ingots produced by non-consumable electrode argon arc melting. The results show that small quantities of β phase are distributed along γ/α₂ lamellar colony boundaries as discontinuous network in the TiAl alloys owing to the segregation of Mo element. The γ phase forms in the interdentritic microsegregation area when the Mo addition exceeds 0.8%. The β and γ phases can be eliminated effectively by subsequent homogenization heat treatment at the temperature above T_α. The evolution of the strength, microhardness and ductility at different Mo contents under as-cast and as-homogenization treated conditions was analyzed, indicating that excessive Mo addition is prone to cause the microsegregation, thus decreasing the strength and microhardness obviously, which can be improved effectively by subsequent homogenization heat treatment.     

Effect of Annealing Treatments on the Microstructure,Mechanical Properties and Corrosion Behavior of Direct Metal Laser Sintered Ti-6Al-4V

An experimental investigation on the effects of post-annealing treatments on the microstructure, mechanical properties and corrosion behavior of direct metal laser sintered Ti-6Al-4V alloys has been conducted. The microstructure and phase evolution as affected by annealing treatment temperature were examined through scanning electron microscopy and x-ray diffraction. The tensile properties and Vickers hardness were measured and compared to the commercial Grade 5 Ti-6Al-4V alloy. Corrosion behavior of the parts was analyzed electrochemically in simulated body fluid at 37 °C. It was found out that the as-printed parts mainly composed of non-equilibrium α′ phase. Annealing treatment allowed the transformation from α′ to α phase and the development of β phase. The tensile test results indicated that post-annealing treatment could improve the ductility and decrease the strength. The as-printed Ti-6Al-4V part exhibits inferior corrosion resistance compared to the commercial alloy, and post-annealing treatment can reduce its susceptibility to corrosion by reducing the two-phase interface area.     

Effects of yttrium on microstructures and properties of Ti- 17Al-27Nb alloy

1 Introduction With the rapid development in aerospace technology, the aero engine components have to endure larger force and higher temperature due to speed increase of aero-craft. Therefore, more requisitions have to be presented when selecting material…     

定向凝固Ti-45Al-7Nb合金的组织特征

研究了液态金属冷却定向凝固条件下Ti-45Al-7Nb(at%)合金的组织特征。结果表明:定向凝固过程中合金的凝固路径及稳态区片层取向均受到抽拉速率的影响。当抽拉速率为0.36mm/min时,合金的初生相为α相,与生长方向垂直的片层组织生长占优;抽拉速率介于1～10mm/min时,合金初生相变为β相,凝固过程中会经历β单相区,片层取向多为与生长方向成0°和45°;当抽拉速率增加至20mm/min时,合金初生相仍为β相,随后发生L+β→α包晶反应,与抽拉方向之间的夹角介于45°～75°之间的片层组织生长占优。     

Phase equilibria in Ti3Al-Nb alloys at 1000 °C

Titanium aluminides are considered to be the future high-temperature structural materials for turbine applications. Major focus is on α₂Ti₃Al based and γTiAl based alloys. Niobium additions to Ti₃Al alloys is found to improve the room-temperature ductility. Thus phase equilibria in Ti-Al-Nb system is of practical significance with regard to their processing and high-temperature phase stability characteristics. In the present research, four alloys with compositions Ti-22Al-12Nb, Ti-21A1-16Nb, Ti-20Al-20Nb, and Ti-25Al-25Nb (all in atom percent) were equilibrated at 1000 °C for 225 hours and then quenched in water. The quenched alloys were characterized for phase relations by optical microscopy, X-ray diffraction (XRD), and electron probe microanalysis (EPMA). Based on the phase analysis, the ternary isotherm of the Ti-Al-Nb system at 1000 °C was constructed on the Ti₃Al-rich side. The orthorhombic Ti₂AlNb phase was observed in the sample with Ti-25Al-25Nb composition signifying the presence of this phase at 1000 °C.     

Ti-23Al-17Nb激光焊接接头的组织性能研究

通过室温和高温拉伸性能测试研究焊后热处理和同步预热对Ti-23Al-17Nb(原子分数,下同)合金CO_2激光焊接接头性能的影响.结果表明,接头室温和高温拉伸性能低,焊后真空热处理提高接头室温和高温拉伸性能,仍低于母材;同步预热接头室温强度和塑性与母材相当,高温强度与焊后热处理效果相当.组织分析显示,焊缝存在两个腐蚀衬度区,组织为B2相,热影响区晶粒由熔合线到母材逐渐细化,焊后热处理和同步预热改变β相基体上α2相的析出.     

Effects of minor yttrium addition on hot deformability of lamellar Ti-45Al-SNb alloy

The effects of 0.3%（molar fraction, the same below） yttrium addition on hot deformability of lamellar Ti-45Al-5Nb alloy were investigated by simulated isothermal forging tests. The ingots with the nominal compositions of Ti-45Al-5Nb and Ti-45Al-5Nb-0.3Y were prepared by induction skull melting. Simulated isothermal forging tests were conducted on Gleeble 1500D thermo-simulation machine using a 6 mm in diameter and 10 mm in length compressive specimen at the deformation temperatures of 1 100, 1 150, 1 200 ℃ and strain rates of 1.0, 0.1, 0.01 s^-1. The results show that yttrium addition remarkably improves hot deformability of Ti-45Al-5Nb alloy. An appropriate hot deformation processing parameter of Ti-45Al-5Nb-0.3Y alloy is determined as 1 200 ℃, 0.01 s^-1. The flow stresses are decreased by yttrium addition under the same compressive conditions. The activation energies of deformation Q are calculated as 448.6 and 399.5 kJ/mol for Y-free and Y-containing alloys, respectively. The deformed microstructure observation under 1 200 ℃, 0.01 s^-1 condition indicates that Ti-45Al-5Nb-0.3Y alloy shows more dynamic recrystallization. The improvement of hot deformability of Ti-45Al-5Nb-0.3Y alloy induced by yttrium addition should be attributed to that the smaller the original lamellar colonies, the lower the deformation resistance and activation energy of deformation are, and the more the dynamic recrystallization is.