Ti2AlNb合金超塑性能及四层立筋结构超塑成形/扩散连接工艺

对Ti-22Al-27Nb合金四层结构件SPF/DB组合工艺进行试验研究,对Ti-22Al-27Nb合金的超塑性能及扩散连接性能进行探究。拉伸实验表明,当变形温度为960℃、应变速率为1×10^?4 s^?1时,材料伸长率达到最大,为230%。对温度、保温时间和扩散压力对Ti-22Al-27Nb合金接头质量的影响进行研究,结果表明Ti-22Al-27Nb合金扩散连接的最佳工艺参数为(960℃,10 MPa,2 h)。根据高温拉伸试验结果,利用有限元模拟软件对中空四层结构件超塑成形过程进行模拟。通过SPF/DB组合工艺成形得到外观质量良好的Ti-22Al-27Nb合金中空四层结构件,成形构件壁厚分布均匀。     

Ti-22Al-25Nb与TC11异种钛合金的线性摩擦焊接

通过Ti-22Al-25Nb(Ti2AlNb基合金)与TC11((α+β)钛合金)的线性摩擦焊接,研究焊接工艺参数对接头外貌及界面结合率的影响,观察接头附近显微组织,并测试了其显微硬度。结果表明,随着焊接工艺参数,如摩擦时间、摩擦频率和摩擦压力的提高,接头的结合率显著提高;在焊接和随后的冷却过程中,TC11合金侧的热影响区域发生了α→β→α′相变,形成的大量针状马氏体α′相使焊缝区的显微硬度值显著增大;Ti-22Al-25Nb合金侧的热影响区域主要发生了(O,α2)→B2/β相变,随着O相和α2相的减少,该区域金属的显微硬度值显著降低。在合适的工艺条件下,线性摩擦焊接Ti-22Al-25Nb合金与TC11合金能够形成质量完好的焊接接头。     

Effect of heat treatment processing on microstructure and tensile properties of Ti-6Al-4V-10Nb alloy

Effects of heat treatment processing on the microstructure and mechanical properties of Ti-6Al-4V-10Nb alloy were investigated. The microstructures were investigated by SEM, TEM and XRD, and the mechanical properties were evaluated by tensile tests at room and elevated temperatures. The results indicate that the lath-like and globular primary α phase, secondary α phase and β phase are obtained after forging and heat treatment processing. The size of secondary α phase is much smaller than that of primary α phase. After heat treatment, the volume fraction of primary α phase is decreased, and that of secondary α phase is increased. With the increase of solution temperature, the volume fraction of primary α phase is gradually decreased, and that of secondary α phase is obviously increased. The yield strength and tensile strength of Ti-6Al-4V-10Nb alloy are significantly enhanced with the solution temperature increasing.     

Microstructure and Mechanical Properties of Unidirectional W Filament Reinforced Al-6Ti-6Nb and SiCp-Al-6Ti-6Nb Matrix Composites

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Characterization of the hot deformation behavior of a Ti-22Al-25Nb alloy using processing maps based on the Murty criterion

Isothermal compression testing of Ti-22Al-25Nb alloy was carried out at deformation temperatures between 940 and 1060 °C with strain rate between 0.001 and 10 s⁻¹, and a height reduction of 50%. The hot deformation behavior of Ti-22Al-25Nb alloy was characterized based on an analysis of the stress-strain behavior, kinetics and the processing map, for obtaining optimum processing windows and achieving desired microstructures during hot working. The constitutive equation was established, which described the flow stress as a function of the strain rate and deformation temperature. The apparent activation energies were calculated to be 788.77 kJ/mol in the α₂ + β/B2 + O phase region and 436.23 kJ/mol in the α₂ + B2 phase region, respectively. Based on Dynamic Material Model and the Murty instability criterion, the processing map for the Ti-22Al-25Nb alloy was constructed for strain of 0.6. The map exhibits a stable domain for the temperature range of 940-1060 °C and strain rate range of 0.001-0.1 s⁻¹ with two peaks in power dissipation of 51 and 56%, occurring at 940 °C/0.001 s⁻¹ and 1060 °C/0.001 s⁻¹, respectively. One is associated with lamellar globularization, and the other displays a phenomenon of recrystallization. Therefore, the desired processing condition of the Ti-22Al-25Nb alloy is 940 °C/0.001 s⁻¹ in the α₂ + β/B2 + O phase field. Moreover, the material also undergoes flow instabilities at strain rates higher than 1 s⁻¹. This instability domain exhibits flow localization and adiabatic shear bands which should be avoided during hot processing in order to obtain satisfactory properties.     

YbB6 对Ti-6Al-4V钛合金组织和性能的影响

采用放电等离子烧结（SPS）制备了含YbB₆的Ti-6Al-4V钛合金,并研究了YbB₆对Ti-6Al-4V钛合金显微组织和力学性能的影响。结果表明,随着YbB₆含量的增加,复合材料的显微组织发生转变,晶粒明显细化,原位反应生成的TiB晶须和Yb₂O₃颗粒有利于复合材料力学性能的提高。此外,当添加0.6%（质量分数）YbB₆后,烧结样品的相对密度、显微硬度、屈服强度、极限拉伸强度和延伸率分别为99.43%、4030 MPa、903 MPa、1148 MPa和3.3%。与Ti-6Al-4V试样相比,其数值分别提高了0.37%、13.8%、38.07%和17.14%。强化机制主要是组织转变、晶粒细化和弥散强化。随着YbB₆含量的增加,断裂方式主要为韧性断裂和脆性断裂。     

Wire based additive layer manufacturing: Comparison of microstructure and mechanical properties of Ti-6Al-4V components fabricated by laser-beam deposition and shaped metal deposition

The microstructure and the mechanical properties of Ti-6Al-4V components, fabricated by two different wire based additive layer manufacturing techniques, namely laser-beam deposition and shaped metal deposition, are presented. Both techniques resulted in dense components with lamellar α/β microstructure. Large ultimate tensile strength values between 900 and 1000 MPa were observed. The strain at failure strongly depends on the orientation, where highest values up to 19% were obtained in direction of the building direction. Heat treatment increased the highest strain at failure up to 22%. The fatigue limit was observed to be higher than 770 MPa.     

Ti-6Al-4V合金高温氧化行为及显微组织研究

分析了Ti-6Al-4V合金在900 _oC,930 _oC,960 _oC温度下的氧化行为及表层显微组织变化。在0.5-24 h时间内,氧化层不断增厚,越靠近表面氧化层越疏松。氧含量在氧化层/富氧层界面的5 μm内发生急剧下降,进入富氧层后缓慢下降直到稳定。氧化层中以TiO₂为主,同时也出现了Al₂O₃。富氧层中的a相含量远远高于基体内部,其晶粒尺寸也发生长大。富氧层深度与热暴露时间的关系可用对数函数描述,通过线性回归分析计算出了O在富氧层中的扩散激活能为206 kJ/mol。     

B元素对Ti-46Al和Ti-46Al-5Nb合金柱状晶组织的影响

B元素对Ti-46Al和Ti-46A1-5Nb(原子分数,%)合金的柱状晶组织均有明显的细化作用,且对后者的细化效果更显著.这一现象可归结为:B元素在Ti-46Al-5Nb合金中的溶解度较低,硼化物析出量增加,柱状晶组织进一步细化.     

热循环对Ti-6Al-4V合金显微组织与疲劳性能的影响

对Ti-6Al-4V轧制板材依次进行了920_oC, 800_oC, 850_oC, 900_oC四次热循环,研究了材料在每次热循环后的显微组织及微观织构的演变,并对热循环前后的拉伸和旋转弯曲疲劳性能进行了比较。结果表明,原材料中存在的长条a相发生再结晶后趋于等轴化,其组织不均匀性在920_oC,800_oC两次热循环后得到根本性改善,再经历850_oC, 900_oC两次热循环后,初生a相进一步等轴化并稍有长大,其体积分数维持稳定。原材料具有较强的横向织构,有多个平行于轧制方向的宏观带存在,导致了轧向的疲劳性能优于横向,中值疲劳极限分别为497MPa/474MPa。热循环后横向织构强度有所减弱,并且出现了一定程度的(0001)基面织构。经历4次热循环后,材料的显微组织发生粗化,拉伸强度降低了约20MPa,轧向/横向的中值疲劳极限下降至441MPa/441MPa。     

基于模糊理论的Ti-22Al-25Nb合金高温本构关系模型

运用Gleeble1500热模拟实验机对Ti-22Al-25Nb钛合金试样进行热模拟压缩试验,针对该合金高温变形过程时复杂的流变行为,以实验所得数据(变形温度940～1030℃,应变速率0.001～10s-1)为基础,从模糊集理论的本质特征出发,提出了一种基于模糊动态线性原理的本构模型,并与实验结果进行了对比。结果表明:基于模糊集理论建立的Ti-22Al-25Nb合金的高温本构关系模型是切实可行的,拟合程度较高,弥补了传统回归模型不能反映变形全过程的局限性,是一种有广泛应用前景的表征工程材料本构关系的便捷有效的方法。     

Ti_2AlNb相合金Ti-22Al-25Nb的TLP扩散连接

以Ti-15Cu-15Ni合金薄带作中间层,用Gleeble 1500D热-力学模拟试验机对Ti2AlNb相合金Ti-22Al-25Nb进行TLP扩散连接。研究了连接参数对接头组织演变、元素分布、接头强度及其断裂特征的影响。结果表明,接头形成过程由5个阶段组成,Nb是接头成分均匀化的扩散主控元素。适当延长保温时间和适当提高连接温度有利于获得组织与成分均匀的高强接头。保温结束后接头快速冷却时,其连接区室温组织为B2相;而采用慢冷工艺有利于促进高温β相的相变从而改善连接区组织,室温组织为B2相基体和少量α2、O相。连接温度和保温时间分别为990℃和90min且采用慢冷工艺时,接头的室温和650℃抗拉伸强度分别为1041MPa和659MPa,分别达到原始母材强度的95％和81％,明显高于采用快冷工艺的接头强度。     

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.     

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…     

工艺参数设置和厚度对电子束熔融加工Ti-6Al-4V合金微观结构的影响

研究了试件尺寸和工艺参数(电子束强度,扫描速度,焦点偏移量和扫描长度)对电子束熔融(EBM)加工Ti-6Al-4V合金微观结构的影响。结果表明,可以观察到EBM加工的Ti-6Al-4V合金的微观结构由原始β相的柱状晶粒组成。在柱状晶粒内部观察到典型的(α+β)结构,即魏氏体α片和在细小的α晶粒的界面上形成的杆状β相。还发现沿原始β柱状晶粒的晶界形成的α层晶界。随着试件厚度、电子束能量密度和扫描长度的增加,先前的β柱状晶粒的直径增大,并且生长的方向与加工方向一致。同时,柱状晶粒直径随着试件高度的增加而减小。随着试件厚度和电子束能量密度的增加,α片会变得更粗大。     

用热扩散方法在Ti-6Al-4V合金表面获得铝化物和硅化物涂层

采用固体粉末包装热扩散方法,对Ti-6Al-4V合金分别进行表面渗铝和渗硅处理,以提高该合金的抗高温氧化性能。结果表明:Ti-6Al-4V合金表面形成的铝化物涂层的金相组织为单层结构,其上有少量贯穿裂纹存在;主要相结构是TiAl_3。而硅化物涂层的金相组织则为双层结构,外层较厚,呈柱状晶,由TiSi_2相组成;内层则较薄,由Ti_5Si_4相组成。表面渗铝和渗硅处理都可以大大提高Ti-6Al-4V合金的抗高温氧化性能。     

反应烧结Ti-22Al-25Nb合金的高温氧化行为

Ti-22Al-25Nb是一种高温结构材料,它的抗氧化性对今后的发展和应用具有重要意义。采用元素粉末和反应烧结法制备了Ti-22Al-25Nb烧结合金,研究了其在静态空气中的氧化行为(923~950℃温度范围内)。不同温度(650 °C, 750 °C, 850 °C, 950 °C)下的最大增重分别为0.15 mg﹒cm-2、0.41 mg·cm-2、1.68 mg·cm-2和6.9 mg·cm-2。研究发现Ti-22Al-25Nb烧结合金具有良好的抗氧化性,特别是在750°C以下（950°C时发生氧化分解）。根据氧化动力学分析,在750℃以下,氧化行为大致遵循抛物线规律,而在850℃以上,氧化行为符合线性规律。讨论了铌合金元素对氧化动力学的影响,通过对氧化形态和相的观察和分析,证明O相（有序Ti2AlNb相）的抗氧化性能优于其它相,其原因可以解释为不同相的Nb含量的差异导致抗氧化性的差异。     

Vacuum diffusion bonding of Ti2AlNb alloy and TC4 alloy

The Ti₂AlNb alloy was joined with TC4 alloy by vacuum diffusion bonding. The relationship between bonding parameters, and joint microstructure and shear strength was investigated. The results indicated that the diffusion of Al, Ti, Nb and V elements across bonding interface led to the formation of three reaction layers: B2/β layer and α₂ layer on the TC4 side, and α₂+B2/β layer on the Ti₂AlNb side. The bonding temperature determined the atomic activity, thus controlling the growth of reaction layers and influencing the shear strength of the joint. When the Ti₂AlNb alloy and TC4 alloy were bonded at 950 °C for 30 min under 10 MPa, the shear strength of the joint reached the maximum of 467 MPa. The analysis on the fracture morphology showed that the fracture occurred within the B2/β layer and the fracture model was ductile rupture. Meanwhile, the formation mechanism of the Ti₂AlNb/TC4 joint was discussed in depth.     

HIP diffusion bonding of P/M titanium alloy Ti-6Al-4V and stainless steel 1Cr18Ni9Ti

The HIP diffusion bonding of P/M titanium alloy Ti-6A1-4V and stainless steel 1Cr18Ni9Ti using pure Ni as intermediate layer was studied. Bonding joint with complex bonding interface was obtained by HIPing pre-alloyed Ti-6Al-4V powders and stainless steel 1Crl 8Ni9Ti in a vacuum canning. The joint strengths were examined and the characteristics of bonding joint were observed. The result shows that the maximized strength of HIP diffusion bonding between P/M titanium alloy Ti-6Al-4V and stainless steel 1Cr18Ni9Ti can be up to 388 MPa and the microstructure of bonding joint is acceptable.     

Diffusion bonding of Ti-2.5Al-2.5Mo-2.5Zr and Co-Cr-Mo alloys

A solid state diffusion bonding between two metallic biomaterials, Ti-2.5Al-2.5Mo-2.5Zr alloy and Co-Cr-Mo alloy (F75), has been investigated by using energy-dispersive spectrometer analysis, metallographic observation and bonding strength evaluation. The experiments indicate that bonded at 750 °C leads to insufficient atoms diffusion and weak bond. When bonded at 900 °C some intermetallics, CoTi₂, Co₂Ti, and Cr₂Ti, form in the diffusion zone, which significantly deteriorate the plasticity and lead to lower bonding strength. A high bonding strength can be achieved when bonding at 850 °C for 60 min. During the bonding process each element exhibits various diffusion velocity in the opposite alloy. The diffusion coefficients for those elements can be ranked in following sequence: D_Co > D_Cr > D_Mo in the Ti-2.5Al-2.5Mo-2.5Zr alloy and D_Ti > D_Al > D_Zr in the Co-Cr-Mo alloy.