胶接对Al-Li-S4铝合金织构的影响

将新一代Al-Li-S-4铝锂合金用砂纸打磨,用磷酸进行阳极化处理,用环氧320/322胶胶接,然后以12℃/min的速率升温至120℃,保温固化1 h。采用BrukerD8 Discover型X射线衍射仪测定胶接固化后的织构,并与未胶接的Al-Li-S-4合金进行比较。结果表明:胶接后合金主要织构的成分没有发生大的变化,但在胶接应力的作用下织构的位置发生变化。其中,黄铜织构与铜织构较稳定,而立方织构的取向密度变化较大,位置也有所改变。通过研究胶接对材料织构的影响,了解材料内部应力及晶粒取向上的变化,为胶接工艺的制定及改进提供参考。     

锻造方式对Ti-6Al-4V合金组织及取向分布的影响

在快锻液压机上对Ti-6Al-4V合金进行了锻造变形,采用扫描电镜、背散射电子衍射技术以及X射线衍射技术研究了不同锻造方式下合金组织及晶粒取向的变化规律.在单向镦拔和换向镦拔两种不同锻造方式下,难变形区、小变形区及大变形区中α相及β相的分布差别不大,组织均匀性基本一致,两种变形方式下锻坯不同区域的应变稍有差别.进一步对不同变形区域形变织构的定量分析可知:在应变较小的边缘区域,变形主要以{0001}基面滑移为主,形成基面织构;在应变较大的内部区域,织构明显转向{11相似文献   

热挤压工艺对Ti-6Al-4V钛合金组织与性能的影响

研究了挤压温度和挤压比对Ti-6Al-4V钛合金挤压型材显微组织、织构及力学性能的影响.挤压温度在相变点T_β以上150~350℃、挤压比λ为25~85范围内时,型材动态再结晶均已完成,形成均匀的魏氏组织.型材的晶粒随挤压温度的降低和挤压比的提高而细化.型材织构在挤压比较低(λ=25)时强度较弱且为随机分布;当挤压比增加时,织构增强并有形成(相似文献   

Ti-6Al-4V合金表面预处理研究

近年来,复合材料以其优异的结构强度和性能在新一代飞机上显示出巨大的应用前景。然而,碳纤维复合材料在与金属铝接触时易发生接触腐蚀,并向金属内部扩散。而金属钛表面可以迅速生成纳米级氧化层,并且即使该氧化层受到破坏,在有氧或水的情况下又可以重新生成新的氧化层,从而避免在与碳纤维复合材料接触时被腐蚀。由于复合材料具有较高的缺口敏感度,因此,碳纤维复合材料     

水基凝胶注Ti-6Al-4V合金坯体

将凝胶注模工艺应用于金属Ti6Al4V合金粉末的成形,研究了高固相含量的Ti6Al4V合金粉末的料浆的制备,比较了金属浆料与陶瓷浆料的不同。结果表明粉末的颗粒形状是影响浆料固相含量的重要因素,浆料的固相含量随分散剂的增加而增加。最后制备出了固相含量为54%(体积分数,下同)的钛合金粉末浆料和形状复杂的坯体。坯体的抗弯强度随气雾化(GA)Ti6Al4V含量增加先增大后减小,随着坯体的固相含量增大而减小。当GA-Ti6Al4V含量为80%,固相含量为50%时生坯抗弯强度最大,为18.5 MPa。     

Ti-6Al-4V合金加工

Ti-6Al-4V合金是用途最广泛的钛合金,在航空、汽车、能源、舰船、化工、医疗器械及体育用品等所有应用领域中,该合金占到50%以上。在航空业中,Ti-6Al-4V合金用作重要的零部件,从隔板、机翼、机架到压气机盘、发动机、叶片、气瓶。例如,Ti-6Al-4V在美国F22“猛禽”战斗机总重中占36%。因此,对Ti-6Al-4V零部件进行设计并改进热加工工艺有助于大大降低成本。1 Ti-6Al-4V合金的级别Ti-6Al-4V合金根据间隙元素含量被划分成两种级别,它们之间的主要差异是氧含量不同。工业级Ti-6Al-4V中氧的质量分数为0.16%~0.20%;超低间隙(ELI)…     

Ti-6Al-4V合金的时效组织与硬度研究

本文研究了明Ti-6Al-4V合金在510℃下不同时间时效后组织及硬度变化。结果发现该合金在940℃固溶、510℃时效时，先从亚稳定β相中析出近等轴状的α相；延长时效时间，α相向片状生长，形成α集团，在集团内片状α的取向趋于一致，而集团间的取向不一致，这导致合金的硬度增加；继续增加时效时间，发生马氏体的分解，片状α相向等轴状转变，合金硬度降低。538℃时效时，硬度比510℃时高。采用多弧离子镀在Ti-6Al-4V合金表面形成了一层很薄且致密的(Ti，Al)N层，镀层可提高合金的显微硬度。     

添加硼对铸造Ti-6Al-4V合金电火花加工性的影响

钛和钛合金具有高比强度和较高的刚度,广泛应用在航空领域。其中,Ti-6Al-4V合金的应用最为广泛。然而铸态下的β晶粒较大(约为2.5 mm),不利于改善合金的机械性能。为了提高合金的性能,通常采用热机械处理来获取较小晶粒,需要较高的     

电子束选区熔化技术制备Ti-6Al-4V合金的研究进展

钛及钛合金因比强度高、耐腐蚀、生物相容性好等特点被广泛应用于航空航天、生物医疗等领域。电子束选区熔化技术（Selective electron beam melting,SEBM）是近年来发展起来的一种粉末床熔融增材制造技术,具有能量密度高、生产效率快、成形应力低、真空环境下洁净度高等特点,利用该方法制备出的钛及钛合金成为学术界及工程界的研究热点。本文综述了国内外电子束选区熔化技术制备Ti-6Al-4V合金的研究进展,重点从缺陷、显微组织及力学性能进行了分析,最后对电子束选区熔化技术的发展及应用进行了展望。     

Ti-6Al-4V合金置氢动力学与氢分布规律

通过Ti-6Al-4V合金750℃条件下的置氢实验,分析了置氢过程的动力学规律,利用光学金相显微镜和二次离子质谱仪研究了保温时间对氢分布的影响规律.结果显示,Ti-6Al-4V合金置氢动力学遵循二维扩散机制,满足Valensi方程g(α)=α+(1-α)ln(1-α),氢在试样径向方向的二维扩散是置氢反应的控制步骤.置氢保温时间大于60min时,氢压趋于稳定,氢在试样径向方向的二维扩散停止,试样中心的微观组织和氢离子强度与边缘的相一致,氢均匀分布于试样当中.     

Superplastic deformation of Ti-6Al-4V alloy

The alloy Ti-6-Al-4V deforms superplastically in the temperature range 750 to 950° The most important factor which is responsible for superplastic behavior was found to be the very fine grain size. Strain rate has no direct effect on superplasticity, however when the strain rate is very low (approximately 2 × 10 s), prolonged exposure to high temperature causes grain growth and early failure. The strain rate sensitivity factorm = 0.5 and the apparent activation energyAH = 45,000 cal/mole, which is approximately the same as the activation energy for grain boundary self diffusion of titanium. Both values are independent of strain rate within the range 10 - 2.5 × 10 s. All the experimental points fall in a straight line when plotted as log (εkTd* ²/D_gbGb³) vs log (σ/G) with a slopen = l/m = 2. This is in excellent agreement with the theory of grain boundary sliding accommodated by dislocation motion.     

High-temperature mechanical behavior of Ti-6Al-4V alloy and TiC p /Ti-6Al-4V composite

Mechanical behaviors at 538 °C, including tensile and creep properties, were investigated for both the Ti-6Al-4V alloy and the Ti-6Al-4V composite reinforced with 10 wt pct TiC particulates fabricated by cold and hot isostatic pressing (CHIP). It was shown that the yield strength (YS) and ultimate tensile strength (UTS) of the composite were greater than those of the matrix alloy at the strain rates ranging from approximately 10⁻⁵ to 10⁻³ s⁻¹. However, the elongation of the composite material was substantially lower than that of the matrix alloy. The creep resistance of the composite was superior to that of the matrix alloy. The data of minimum creep strain rate vs applied stress for the composite can be fit to a power-law equation, and the stress exponent values of 5 and 8 were obtained for applied stress ranges of 103 to 232 MPa and 232 to 379 MPa, respectively. The damage mechanisms were different for the matrix alloy and the composite, as demonstrated by the scanning electron microscopy (SEM) observation of fracture surfaces and the optical microscopy examination of the regions adjacent to the fracture surface. The tensile-tested matrix alloy showed dimpled fracture, while the creep-tested matrix alloy exhibited preferentially interlath and intercolony cracking. The failure of the tensile-tested and creep-tested composite material was controlled by the cleavage failure of the particulates, which was followed by the ductile fracture of the matrix.     

Influence of texture on fatigue properties of Ti-6Al-4V

Tensile properties, high cycle fatigue strength, and fatigue crack propagation behavior were evaluated on highly textured Ti-6Al-4V material to investigate the influence of a preferred crystallographic orientation on mechanical properties. Thermomechanical treatments were used to develop three different textures: a basal, basal/transverse, and transverse type, all of which exhibited the same homogeneously equiaxed microstructure. The Young’s modulus was found to vary between 107 and 126 GNm^-2, and yield strength changed from 1055 to 1170 MNm^-2. Ductility was only slightly affected by texture. High cycle fatigue and fatigue crack growth measurements were performed in vacuum, laboratory air, and a 3.5 pct NaCl solution. It is shown that laboratory air can be regarded as a quite corrosive environment. In vacuum the highest fatigue strength values were measured whenever loads were perpendicular to basal planes. However, these conditions had the highest susceptibilities to air and 3.5 pct NaCl solution environments. Nearly no influence of texture on fatigue crack propagation was found in vacuum, but in a corrosive environment crack growth parallel to (0002)-planes was much faster than perpendicular to these planes. To explain the corrosive effect on the fatigue properties of the textured material hydrogen is thought to play a key role.     

Mechanochemical processing of nanocrystalline Ti-6Al-4V alloy

Synthesis of nanocrystalline Ti-6Al-4V was explored using mechanochemical processing. The reaction mixture was comprised of CaH₂, Mg powder, anhydrous AlCl₃, anhydrous VCl₃, and TiCl₄. The milled powder (reaction product) primarily consisted of nanocrystalline alloy hydride having a composition (Ti-6Al-4V)H_1.942, along with MgCl₂ and CaCl₂ as by-products. Aqueous solutions of nitric acid, sulfuric acid, and 1 pct sodium sulfite were found to be very effective in leaching of the chlorides from the milled powder. The (Ti-6Al-4V)H_1.942 on dehydrogenation at 375°C resulted in nanocrystalline Ti-6Al-4V alloy powder.     

Effect of hydrogen on the low-temperature creep of a submicrocrystalline Ti-6Al-4V alloy

The effect of alloying with 0.002–0.24 wt % H on the creep of the Ti-6Al-4V alloy at a temperature of ∼0.15T _m (T _m is the melting temperature) is studied. The formation of a submicrocrystalline structure in the alloy is found to increase the stress-rupture strength and the hydrogen embrittlement resistance. Possible causes of the increase in the deformation localization resistance of the alloy in the presence of hydrogen in a solid solution are discussed.     

Roll bonding behaviour of Ti-6Al-4V sheets during pack rolling

Low density, excellent corrosion resistance, moderate strengths at high temperatures make titanium based alloys candidate materials for advanced aerospace structures. Advanced joining techniques are emulating for fabrication of complex aerospace structures. Roll bonding is one such solid state joining technique where bonding between two rough and clean surfaces is obtained under high temperature and pressure. The work horse dual phase titanium alloy Ti-6Al-4V finds extensive structural application in aerospace and space industries. In the present study, two Ti-6Al-4V sheets are stacked together and encapsulated in a mild steel can followed by evacuation and hot crimping. The pack is extensively deformed to ∼84% reduction in thickness employing conventional hot rolling mill. Partially roll bonded 0.74mm thick sheets were obtained and microstructural evolution was studied using light microscopy and scanning electron microscopy. The incompletely bonded interface was analyzed through elemental mappings by Electron Probe Micro Analyzer and compared with completely bonded region. The partially bonded region revealed the presence of aluminium oxide at the interface which possibly could have hindered complete bonding at that region. The room temperature tensile properties of as- roll bonded Ti-6Al-4V nearly approaches the base material properties.     

Deformation kinetics of the Ti-6Al-4V alloy at low temperatures

The deformation kinetics of theα + β titanium alloy Ti-6 A1-4V were investigated over the temperature range of 4.2 to 760 K. It was found that the Gibbs free energy of activation AG at 0 K and zero effective stress is ∼ 1.3 eV (∼ 1.25 × 10⁵ J/mole) (∼0.17 μ_ob³), the maximum force for the dislocation-obstacle interaction is ∼ 80 × 10^-6 dyne (∼ 80 × 10^-11N) (∼ 0.19 μ_ob²) and the activation distance x₀ ^* at which the force first rises rapidly ∼ 1.5b. These quantities, and others, are the same as those for unalloyed titanium, where it was established that interstitial solutes are the obstacles controlling the dislocation motion. The results for the Ti-6A1-4V alloy are in slightly better accord with ρG being independent of temperature than proportional to the shear modulus, but the evidence is not conclusive. Former Graduate Student, Metallurgical Engineering and Materials Science Department, University of Kentucky. Formerly Research Associate, Metallurgical Engineering and Materials Science Department, University of Kentucky     

Thermal cycling behavior of as-quenched and aged Ti-6Al-4V alloy

Thermal cycling tests between 77 and 623 K were performed on Ti-6Al-4V alloy; the tensile properties were evaluated, and transmission electron microscopy (TEM) microstructural analysis was performed both before and after thermal cycling. Thermal cycling (1000 cycles) promptly increases the strength of the as-quenched alloy, induces a slight decrease in strength for the near-peak-aged alloy, and makes no change for that of the overaged alloy. The elongation of the alloy in all heat-treated conditions decreases after 1000 thermal cycles. The loss of fracture elongation of the asquenched alloy is the largest, but the residual ductility is the highest. The loss of fracture elongation for the near-peak-aged alloy is lower, and the residual plasticity is higher than those for the overaged alloy.     

Cavitation-Induced erosion of Ti-6Al-4V

Cavitation-induced erosion has been examined in Ti-6A1-4V in the mill annealed, solution-treat and aged, and beta annealed conditions. Weight loss data show only small differences between heat treatments with the solution-treat and aged microstructure exhibiting the lowest weight loss rates. Sequential micrographs of the same specimen area as a function of erosion time show that initial fracture occurs along the α-β interfaces and along crystallographic slip bands in the α-phase. The early stages of erosion are also dependent on the orientation of the Widmanstatten colonies in the beta annealed condition. These observations strongly suggest that fatigue fracture is important, at least in the early stages of the cavitation erosion process. Depression of the softer α- phase also occurs at short exposure times, and this facilitates fracture and removal of the exposed material;i.e., β-phase or tempered martensite. Examination of the eroded surfaces in the later stages where considerable material has been removed shows little evidence of the underlying microstructure, despite the distinct differences in the micro-structures of the samples tested. Formaly Undergraduate Students at Michigan Technological University