Superplastic Forming and Diffusion Bonding for Sandwich Structure of Ti-6Al-4V Alloy

Superplastic forming and diffusion bonding (SPF/DB) is a well-established process for the manufacture of components almost exclusively from Ti-6AI-4V sheet material. The sandwich structure of Ti-6AI-4V alloy is investigated. The effects of the microstructure on the SPF/DB process were discussed. The microstructure at the interfaces and the distribution of thickness were researched.     

Influences of processing parameters and heat treatment on microstructure and mechanical behavior of Ti-6Al-4V fabricated using selective laser melting

Selective laser melting (SLM) has provided an alternative to the conventional fabrication techniques for Ti-6Al-4V alloy parts because of its flexibility and ease in creating complex features. Therefore, this study investigated the effects of the process parameters and heat treatment on the microstructure and mechanical properties of Ti-6Al-4V fabricated using SLM. The influences of various process parameters on the relative density, tensile properties, impact toughness, and hardness of Ti-6Al-4V alloy parts were studied. By employing parameter optimization, a high-density high-strength Ti-6Al-4V alloy was fabricated by SLM. A relative density of 99.45%, a tensile strength of 1 188 MPa, and an elongation to failure of 9.5% were achieved for the SLM-fabricated Ti-6Al-4V alloy with optimized parameters. The effects of annealing and solution aging heat treatment on the mechanical properties, phase composition, and microstructure of the SLM-fabricated Ti-6Al-4V alloy were also studied. The ductility of the heat-treated Ti-6Al-4V alloy was improved. By applying a heat treatment at 850 ℃ for 2 h, followed by furnace cooling, the elongation to failure and impact toughness were found to be increased from 9.5% to 12.5%, and from 24.13 J/cm² to 47.51 J/cm², respectively.The full text can be downloaded at https://link.springer.com/article/10.1007/s40436-022-00389-y     

增材制造Ti-6Al-4V合金组织调控研究现状

增材制造技术可实现复杂钛合金零件的快速成形,制造的Ti-6Al-4V合金具有较高的强度以及优异的高温性能,被广泛应用于航空、医疗等各大领域。综述了金属增材制造的典型工艺,分析了Ti-6Al-4V合金的相变特征,总结了选区激光熔化制造Ti-6Al-4V的力学性能和组织调控方法,着重分析了热处理温度、冷却速率、变质处理以及超声冲击等对合金组织的影响;展望了增材制造Ti-6Al-4V合金的主要发展方向。     

Ti-6Al-4V合金表面超声振动滚压强化研究

采用超声振动滚压加工技术对Ti-6Al-4V合金表面进行处理,探究该项技术对Ti-6Al-4V合金表面质量的影响。通过对该工艺加工前后的Ti-6Al-4V合金进行表面粗糙度参数、XRD图谱、截面微观形貌、表层残余应力及显微硬度的对比分析,结果表明:经该工艺处理后的合金表面各项粗糙度参数皆有明显降低;加工后的合金表面XRD图谱的衍射峰减弱且宽化,衍射角向高角度方向偏移;加工后的合金表层β相组织相较加工前明显细化,且随着深度增加β相组织逐渐增大;在距离表面约50μm位置的残余应力值最大可达到-967 MPa;加工后的合金表面显微硬度可达到421HV,且在0~140μm的深度范围内,显微硬度随着深度的增加逐渐减小至与基体硬度一致。经超声振动滚压加工后的Ti-6Al-4V合金表面质量显著提高,有利于提高其零部件的使用性能。     

Improved properties of Ti-6Al-4V by combining isothermal equal-channel angular processing and hot-extrusion

The aim of this work was to study effects of hot extrusion on the microstructure of Ti-6Al-4V (wt-%) alloy processed by ECAP. Firstly, an isothermally Ti–6Al–4V alloy processed by Equal channel angular pressing(ECAP) was preheated at 950°C for 6?min and then hot extruded at 900°C. The hot extrusion minimised the grain size and maximised the mechanical strength. Therefore, it was demonstrated that hot extrusion of Ti-6Al-4V alloys that processed by ECAP could be performed without compromising any mechanical properties. Therefore, it is possible to use the ability to apply a reduced cross-section in hot extrusion for an Ti-6Al-4V processed by ECAP without concern about the reduction of properties.     

增材制造Ti-6Al-4V钛合金低周疲劳性能研究进展

金属增材制造技术可用于大型、复杂高性能钛合金结构件的制备,在航空航天等领域具有显著的优势和巨大的发展潜力。虽然增材制造Ti-6Al-4V合金构件的强度已经能够超过锻件,但它仍存在内部孔隙、熔合不良、粗大的柱状晶及残余拉应力等问题,使其在疲劳性能上与锻件具有一定的差距。本文在介绍直接能量沉积、选区激光熔化和电子束选区熔化3种代表性增材制造技术的原理及特点的基础上,简述了3种工艺制备Ti-6Al-4V合金构件的微观组织、静态力学性能及低周疲劳性能的研究进展,重点讨论了打印方向、缺陷、显微组织和表面处理对低周疲劳性能的影响。分析了增材制造Ti-6Al-4V合金构件低周疲劳性能、拉伸性能与微观组织之间的内在关系,并对提高构件低周疲劳性能的方法和推动其广泛应用的发展方向进行展望。     

Ti-SiC Composite and TiC Ceramic Layer Formation on Ti6Al4V Surface by Laser Alloying of Pre-Placed SiC Coating

The Ti-6Al-4V alloy pre-placed with SiC coating was laser alloyed using high power CO2 laser. The laser alloyed cross section shows dendrite and Ti-SiC composite layer microstructure and the respective hardness was 650–800 HV and 1500–2000 HV. The observed hardness was 2 to 7 times greater than that measured on the bulk Ti-6Al-4V substrate. The laser alloyed surface produced high temperature ceramic phases such as TiC, TiSi and Ti5Si3. The elemental analysis was qualitatively estimated using SIMS analysis.     

退火热处理对等径角挤压回收Ti-6Al-4V合金微观结构和显微硬度的影响

采用等径角挤压法回收Ti-6Al-4V合金切屑,并研究了回收样品和退火处理样品的微观结构和显微硬度。结果表明:在回收样品中,切屑之间的边界依然存在,而由于剧烈塑性变形,超细晶结构和较强的纤维织构得以形成。退火处理后,切屑边界部分消失,超细晶组织部分再结晶;而与此同时,退火处理样品展现出更宽泛的织构,再结晶晶粒并不存在择优取向。值得注意的是,退火处理样品的显微硬度较回收样品略有升高。     

Influence of various metal powder mixed dielectric on micro-EDM characteristics of Ti-6Al-4V

Ti-6Al-4V, an advanced engineering material is difficult-to-machine using conventional machining process due to its high strength. It has properties like low weight ratio, outstanding corrosion resistance along with high level of reliable performance in micro components. Micro-electro-discharge machining (Micro-EDM), a popular nontraditional machining process has been identified as the most appropriate machining process for such material. In this paper, the effect of various conducting powders such as copper, nickel and cobalt with different concentrations are mixed with deionized water dielectric, on various responses such as material removal rate (MRR), tool wear rate (TWR), overcut (OC) and taper has been presented. Also, principal component analysis (PCA) has been applied to select the optimal parametric combination of micro-EDM process to achieve optimal values of MRR, TWR, OC and taper during micro-through hole machining. The optimal process parametric setting obtained from the proposed approach is peak current (I_p) of 1.5 A and cobalt (Co) powder concentration of 4 g/L so as to obtain the desired responses. It is also observed from the SEM image that the machined profile and surface topography obtained through the multi-objective optimal parametric combination based on PCA is quite satisfactory and can be applied to achieve geometrically more accurate micro-through holes on Ti-6Al-4V.     

Impact of dressing infeed on SiC wheel for grinding Ti-6Al-4V

Present experimental investigation is directed toward the optimization of dressing infeed for silicon carbide (SiC) wheel to be employed for grinding difficult-to-machine super alloy Ti-6Al-4V. Grinding wheels are dressed using separate, however, identical 0.75 carat single point diamond dressers at 5, 10, 15, 20 and 25 µm infeed values. Differently dressed wheels are consequently, applied for grinding Ti-6Al-4V under different infeed values of 5, 10 and 15 µm. All the operations have been performed at a constant velocity of 1810 m/min. The performances of the differently dressed SiC wheels are evaluated based on the variations of grinding force components, average surface roughness values, grinding ratio, chip forms and based on the analyses of the micrographs of wheel topologies and also of the ground surfaces, obtained using scanning electron microscope. Following the performance evaluation, the optimized dressing infeed has been found to be 20 µm for the operation range considered herein.     

Superplastic deformation characteristics of two microduplex titanium alloys

A comparison of the superplastic deformation behaviour of Ti-6Al-4V (wt%) between 760 and 940‡ C and Ti-6Al-2Sn-4Zr-2Mo between 820 and 970‡ C has been carried out on sheet materials possessing similar as-received microstructures. High tensile elongations were obtained with maximum values being recorded at 880‡ C for Ti-6Al-4V (Ti-6/4) and at 940‡ C for Ti-6Al-2Sn-4Zr-2Mo (Ti-6/2/4/2), under which conditions both alloys possessed aΒ phase proportion of approximately 0.40. For a given deformation temperature the Ti-6/4 alloy had a slightly lower flow stress than the Ti-6/2/4/2, and this was attributed to the lowerΒ phase proportion in the latter alloy. However, at the respective optimum deformation temperatures the Ti-6/2/4/2 alloy had the lower flow stress. The results show that suitably processed Ti-6/2/4/2 alloy is capable of withstanding substantial superplastic strains at relatively low flow stresses, although the optimum deformation temperature is higher for this alloy than for Ti-6/4 material possessing a similar microstructure.     

TI-6Al-4V合金置氢-除氢组织与力学性能

为研究除氢处理对置氢钛合金组织与性能的影响,对Ti-6Al-4V合金在不同参数条件下进行了置氢与除氢处理,采用光学显微镜分析了置氢-除氢处理过程中Ti-6Al-4V合金微观组织的演化规律,通过室温拉伸试验研究了置氢-除氢处理后Ti-6Al-4V合金的力学性能,探讨了Ti-6Al-4V合金置氢-除氢组织与力学性能之间的相...     

Thermo-mechanical sheet metal forming of aero engine components in Ti-6Al-4V – PART 1: Material characterisation

Ti-6Al-4V is one of the most frequently used titanium alloy in aerospace applications such as for load carrying engine structures, due to their high strength to weight ratio in combination with favourable creep resistance at moderate operating temperatures. In the virtual development process of designing suitable thermo-mechanical forming processes for titanium sheet metal components in aero engine applications numerical finite element (FE) simulations are desirable to perform. The benefit is related to the ability of securing forming concepts with respect to shape deviation, thinning and strain localisation. The reliability of the numerical simulations depends on both models and methods used as well as on the accuracy and applicability of the material input data. The material model and related property data need to be consistent with the conditions of the material in the studied thermo-mechanical forming process. In the present work a set of material tests are performed on Ti-6Al-4V at temperatures ranging from room temperature up to 560°C. The purpose is to study the mechanical properties of the specific batch of alloy but foremost to identify necessary material model requirements and generate experimental reference data for model calibration in order to perform FE-analyses of sheet metal forming at elevated temperatures in Ti-6Al-4V.     

The effects of micro arc oxidation of gamma titanium aluminide surfaces on osteoblast adhesion and differentiation

The adhesion and proliferation of human fetal osteoblasts, hFOB 1.19, on micro arc oxidized (MAO) gamma titanium aluminide (γTiAl) surfaces were examined in vitro. Cells were seeded on MAO treated γTiAl disks and incubated for 3 days at 33.5 °C and subsequently for 7 days at 39.5 °C. Samples were then analyzed by scanning electron microscopy (SEM) and alkaline phosphatase assay (ALP) to evaluate cell adhesion and differentiation, respectively. Similar Ti-6Al-4V alloy samples were used for comparison. Untreated γTiAl and Ti-6Al-4V disks to study the effect of micro arc oxidation and glass coverslips as cell growth controls were also incubated concurrently. The ALP Assay results, at 10 days post seeding, showed significant differences in cell differentiation, with P values <0.05 between MAO γTiAl and MAO Ti-6Al-4V with respect to the corresponding untreated alloys. While SEM images showed that hFOB 1.19 cells adhered and proliferated on all MAO and untreated surfaces, as well as on glass coverslips at 10 days post seeding, cell differentiation, determined by the ALP assay, was significantly higher for the MAO alloys.     

基于气体捕捉法的泡沫Ti-6Al-4V等温发泡规律研究

为了确定气体捕捉法制备泡沫Ti-6Al-4V等温发泡过程中孔隙率和微观孔洞的变化规律,在不同发泡温度及发泡时间下制备了泡沫Ti-6Al-4V.运用阿基米德原理对泡沫Ti-6Al-4V的孔隙率进行测量,通过OM和SEM对其微观特征进行观察.研究表明:泡沫Ti-6Al-4V的孔隙率及孔径均随等温发泡温度升高而增加;但当发泡温度大于950℃时,孔隙率和孔径均减小,且孔洞形态由球形变成多边形,这是由于基体内生成大尺寸β相造成的.增加发泡时间能以促进孔洞长大的方式提高泡沫Ti-6Al-4V的孔隙率,球形孔洞数量随着发泡时间的增加逐渐增多.经950℃/10 h发泡得到了孔隙率34.2%、孔径平均值156μm、孔洞为球形且分布弥散的泡沫Ti-6Al-4V.     

选区激光熔化工艺参数对Ti-6Al-4V成形质量的影响

选区激光熔化是一种利用高能束选择性熔化金属粉末进而直接制造复杂几何形状产品的增材制造技术。采用选区激光熔化成形Ti-6Al-4V样品,分析影响选区激光熔化成形质量的主要因素,采用体式显微镜、金相显微镜、扫描电子显微镜(SEM)、显微硬度计系统研究了不同工艺参数对Ti-6Al-4V合金选区激光熔化成形样品的表面形貌、致密度、组织、显微硬度的影响规律。研究得出Ti-6Al-4V合金选区激光熔化成形的优选工艺参数为:扫描功率450W,扫描速度2 500mm/s,扫描间距0.07mm,该工艺参数下打印出的样品具有较为优良的成形质量,致密度高达97.8%,显微硬度平均值为446HV。     

Effect of hot rolling by screw mill on microstructure of a Ti-6Al-4V titanium alloy

The constitute analysis of stress–strain state by the finite element method was carried out by using LS-DYNA software for the axis and surface points of bars of titanium alloy Ti-6Al-4V with lamellar microstructure state, which were processed by screw rolling at a temperature of 940°C with reduction in area of 1.25 and 1.56. The features of screw rolling method that promoted workability of material were investigated. The rolling was performed with 6 passes. Rolling bar was reheated to rolling temperature between each passes for 5 min. The microstructure changes were assessed by light and scanning electron microscopy and quantitative microscopy analysis after each pass of rolling. The different types of deformations (monotonic and cyclic) having the strong influence on microstructures of considered points in the rolled bars are explained. The kinetic of globular structure formation during rolling to total reduction in area of 3.8 was clarified in cross section of bar.     

Surface hardness behaviour of Ti-Al-Mo alloys

The microhardness characteristics of various micro-constituents formed in the Ti-Al-Mo alloys have been investigated. Four alloys having compositions, Ti-40Al-2Mo, Ti-42Al-2Mo, Ti-40Al-6Mo and Ti-42Al-6Mo, have been chosen for this purpose. All of these were heat treated at 1300°C and 1400°C for 1 h and water quenched. All the specimens after above heat treatments have displayed load independent Vickers hardness values (VHN) around 300 g of applied load. The average surface hardness characteristic of the alloys is largely found to be dictated by the phases that are present. The microstructural specific VHN values vary between 600 and 750. The indentation behaviour, however, is governed by the morphologies and length scales of microstructures. The most remarkable finding of the present study pertains to the formation of shear bands around the periphery of the indenter for a finer basket weave microstructure in the Ti-40Al-2Mo. The cluster of finely located slip steps was clearly seen. Such a report is lacking in literature in this class of alloys.     

基于α''组织设计适于激光立体成形的新型高塑性Ti-4.13Al-9.36V合金

为了提高Ti-6Al-4V合金的加工硬化率和塑性,基于其团簇成分式12[Al-Ti₁₂](AlTi₂)+5[Al-Ti₁₄](V₂Ti)设计成分式为4[Al-Ti₁₂](AlTi₂)+12[Al-Ti₁₄](V₂Ti)的(Ti-4.13Al-9.36V, %)合金,采用激光立体成形工艺制备Ti-4.13Al-9.36V和Ti-6.05Al-3.94V(对比合金),研究了沉积态和固溶温度对其显微组织和力学性能的影响。结果表明,沉积态Ti-4.13Al-9.36V和Ti-6.05Al-3.94V合金的显微组织均由基体外延生长的初生β柱状晶和晶内细小的网篮α板条组成。Ti-6.05Al-3.94V合金的初生β柱状晶的宽度约为770 μm,α板条的宽度约为0.71 μm;而Ti-4.13Al-9.36V合金的初生β柱状晶的宽度显著减小到606 μm,α板条的宽度约为0.48 μm。经920℃固溶-淬火处理后Ti-6.05Al-3.94V样品的显微组织为α'+α相,其室温拉伸屈服强度约为893 MPa,抗拉强度约为1071 MPa,延伸率约为3%。经750℃固溶-淬火处理后Ti-4.13Al-9.36V样品的显微组织为α'+α相,与α'马氏体相比,应力诱发的α'马氏体能显著地提高合金的加工硬化能力,其室温拉伸屈服强度约为383 MPa,抗拉强度约为 989 MPa,延伸率达到了17%。这表明,根据团簇理论模型调控α'+α的显微组织能有效提高激光立体成形Ti合金的加工硬化能力和塑性。     

Surface characterization and mechanical property evaluation of thermally oxidized Ti-6Al-4V

The present study concerns development of a thin and adherent oxide film on the surface of Ti-6Al-4V by thermal oxidation. Thermal oxidation was carried out over a range of temperature between 400 to 600 °C and a time from 25 h to 60 h. A detailed characterization of the surface and cross section of the oxidized surface was carried out by optical/scanning electron microscopy and X-ray diffraction techniques. Finally, the mechanical properties of the oxidized surface in terms of microindentation hardness and wear resistance were evaluated as a function of oxidation parameters. Surface oxidation of Ti-6Al-4V at 600 °C for 36 h offered a defect free oxide scale with improved hardness and wear resistance.