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。     

激光冲击强化对Ti6Al4V合金表面完整性和四点弯曲疲劳性能的影响

采用扫描电镜、显微硬度仪、X射线应力测量仪及透射电镜等对激光冲击强化Ti6Al4V合金的表面完整性进行了分析,采用MTS疲劳试验机测试了疲劳性能,并采用扫描电镜分析了疲劳断口,探讨了激光冲击强化机制。结果表明:经功率密度为15.9 GW/cm^2的激光处理后,其四点弯曲中值疲劳寿命较未处理试样提高了4.2~23.5倍;激光功率密度越大,试样的中值疲劳寿命越长。激光冲击强化表现出比喷丸强化更优的疲劳寿命增益效果。经激光冲击强化后,Ti6Al4V合金表面形成了深度为600~1400μm的残余压应力场,表面硬度比未强化区域提高了约10%,且亚表层内部的位错密度也有显著提高。     

Ti6Al4V合金热浸铝研究

采用热浸镀法在Ti6Al4V合金表面制备出TiAl3金属间化合物涂层,并在不同温度下对浸镀后的试样进行热扩散处理.通过XRD、SEM等分析手段对涂层结构和成分进行测试分析,探讨涂层形成机理.结果表明:Ti6Al4V合金经750℃ 5 min热浸铝后,在其表面形成了由纯铝和TiAl3组成的涂层,TiAl3合金层厚约1.5 μm;经550℃退火5h后,TiAl3含量增多而纯铝层含量则相应减少,纯铝层几近消失,合金层厚度约为40μm,涂层致密;经930℃退火5h后,表面的涂层转化为单相的TiAl3,产物纯净,但涂层中出现了较多的孔洞,自涂层表面到钛合金基体,孔洞浓度呈梯度变化.     

激光冲击强化对Ti6Al4V钛合金表面完整性和四点弯曲疲劳性能的影响

研究了激光冲击强化对Ti6Al4V合金表面完整性和四点弯曲疲劳性能的影响,采用扫描电镜、显微硬度仪、X射线应力测量仪及透射电镜等仪器对材料表面完整性进行了分析,采用MTS疲劳试验机对试样进行了疲劳性能测试,并采用扫描电镜分析了疲劳断口,并探讨了激光冲击强化机制。结果表明：采用功率密度为15.9 GW/cm2的激光处理试样后,其四点弯曲疲劳中值寿命较未强化试样提高了4.2～23.5倍;且激光功率密度越大,试样的疲劳中值寿命越长。激光冲击强化表现出比喷丸强化更优的疲劳寿命增益效果。分析发现：经激光冲击强化后,Ti6Al4V合金表面形成了深度约为600~1400 μm的残余压应力场,表面硬度比未强化区域提高了约10%,而亚表层内部的位错密度比未强化试样显著提高,以上表层性能和微观组织的变化对四点弯曲疲劳寿命的提高具有重要作用。     

Multi-dimensional Effect of Heat Treatment on Microstructure and Property of Ti6Al4V Alloy Fabricated by Selective Electron Beam Melting

Metallurgical and Materials Transactions A - The as-built Ti6Al4V component was subjected to a heat treatment of solid solution at 1020 °C for 2 hours and followed by aging at...     

Mechanism of Microarc Oxidation Treated Ti6Al4V Alloy in a Magnetic Field

Metallurgical and Materials Transactions A - The growth kinetics mechanism of microarc oxidation (MAO) coatings on Ti6Al4V alloy in a magnetic field with a low current density of 2 A/dm2...     

Effect of Heat Treatment on the Electrochemical and Mechanical Behavior of the Ti6Al4V Alloy

Metallurgical and Materials Transactions A - The effects of heat treatment on the hardness and electrochemical behavior of the Ti6Al4V alloy were studied. Two heat treatments were performed: one...     

Evidence of Homogeneous Microstructures in Ti6Al4V Alloy During Shear Deformation

Metallurgical and Materials Transactions A - Free-end torsion tests were conducted for Ti6Al4V (Ti64) alloy at temperatures of 298 K, 673 K, and 873 K for different strains ranging from 0.22 to...     

Effect of Nanosecond Laser-Textured Ablation on Performance of Ti6Al4V Alloy Prepared by Composite Nitriding Process

As a widely used orthopedic implant, titanium alloy will face the corrosion of body fluid in human body. In addition, the wear of implants and bones in human body will also reduce the service life of implants. To improve the wear resistance and corrosion resistance of biological titanium alloy, Ti6Al4V alloy was modified by plasma nitriding and plasma-enhanced chemical vapor deposition (PN + PECVD) composite process, and then samples were ablated by nanosecond laser to form a regular surface texture. The textured Ti6Al4V and PN + PECVD samples marked as Ti6Al4V-T and PN + PECVD-T samples. The microstructure and phase composition of the samples before and after modification were observed by scanning electron microscope (SEM), energy-dispersive spectrometer (EDS) and X-ray diffraction (XRD). It was found that after PN + PECVD process, a TiN film with a thickness of 2 μm was formed on the surface of Ti6Al4V. The surface texture of Ti6Al4V-T sample was regular, but the PN + PECVD-T sample texture was wide and shallow irregular after nanosecond laser ablation. The Ti–O and Ti–N–O non-stoichiometric compounds appeared on the samples after nanosecond laser ablation. Through the wear and electrochemical corrosion test in SBF, it was found that PN + PECVD sample had the best wear resistance and corrosion resistance. The wear resistance and corrosion resistance of Ti6Al4V-T and PN + PECVD-T samples were much better than that of Ti6Al4V substrate. The results show that, nitrogen oxides formed on the surface had higher microhardness and surface density, which was beneficial to improve the wear resistance and corrosion resistance of implants.

     

Correlation Between Plasma Electrolytic Oxidation Coating on Ti6Al4V Alloy and Cathode Current

Metallurgical and Materials Transactions A - Plasma electrolytic oxidation (PEO) is a common surface treatment method to improve the properties of titanium alloys. Here, the structure, composition...     

Studies on Characteristics of Ti6Al4V/AA2024 Dissimilar Weld Joint Using Laser Beam Focusing from AA2024 Side

Laser beam welding is based on interaction between the laser beam and parent metals. Methods have been developed in recent years to produce joints of most light metals and their combinations. It provides good weld joint to simplify the structure and reduce the weight and cost to meet the main concerns of the aircraft industry. To achieve these, Ti6Al4V and AA2024 alloy sheets with a thickness of 1.0 mm have been welded with butt joint configuration using pulsed Nd:YAG laser beam welding without groove and filler metal. The weldment has been subjected to testings such as surface roughness, microstructure, hardness, tensile strength and distortion. Test results reveal that laser beam welding is very much suitable for joining Ti6Al4V/AA2024 alloys, while focusing from aluminium side.     

Effect of HIP post-treatment on the HIPed Ti6Al4V powder compacts

Hot isostatic pressing (HIP) is an ideal fabrication technique for products with complex structure, but also a reliable post-treatment method. The individual effect of the HIP or HIP post-treatment (HIPPT) on the mechanical properties of powder compacts have been investigated, but little attention has been paid to their combined effect. In this study, the effect of HIPPT on the densification, microstructure and mechanical properties of HIPed powder compacts were investigated. The relative density shows a regional increase after HIPPT. The interlayer spacing of lamellar α phase is increased, equiaxial grains are coarsened and high-angle grains are decreased. Moreover, an obvious increase in elongation is detected, which demonstrates that HIPPT is beneficial to improve the properties of HIPed powder compacts.     

Ti6Al4V合金表面火焰喷焊W_xC涂层耐磨性分析

采用"一步法"火焰喷焊技术在Ti6Al4V合金表面制备出由Ni60过渡层和W_xC+Ni60强化层组成的喷焊层。喷焊层在氩气气氛中冷却,避免了涂层的氧化。过渡层与基体结合良好,没有孔洞等缺陷;强化层中碳化钨颗粒呈弥散分布,与过渡层界面处存在大量的孔洞。喷焊层硬度为12. 3 GPa,相比基材,硬度提高了近3倍,摩擦系数降低60%以上。喷焊层与GCr15和Si_3N_4对磨后,对磨副GCr15和Si_3N_4磨损严重,而喷焊层无明显磨损,表现出优异的耐磨性。     

氢化钛粉烧结Ti-6Al-4V性能研究

研究了以氢化钛粉与铝钒合金粉为原料,在冷等静压机压制成型后分别采用真空烧结和气氛烧结制备Ti-6Al-4V合金,并对制备的Ti-6Al-4V合金进行相对密度、微观组织及力学性能进行分析。结果表明:在真空条件或气氛条件下烧结制备Ti-6Al-4V合金的相对密度均大于98%,力学性能满足ASTM B348要求;与真空烧结相比,气氛烧结制备的Ti-6Al-4V合金晶粒尺寸较小,力学性能在真空烧结的基础上提高了8%~10%。     

倾斜角度对激光选区熔化成形Ti6Al4V合金的影响

利用自主研发的Di Metal-100型激光选区熔化设备制备与基板平面成不同倾斜角的Ti6Al4V非标准拉伸试样,研究熔化成形后合金的显微组织、物理和力学性能。结果表明,Ti6Al4V合金粉末熔化成形后的组织为针状α′马氏体和(α+β)相,随倾斜角度变化,试样中α/α′相与β相的相对含量也发生变化,倾斜角为45°试样中β相含量最高;α′马氏体呈柱状分布于(α+β)相中,并且方向始终平行于成形方向(Z轴方向)。随SLM成形试样的倾斜角从0°增加到90°,其相对密度先减小后增大,并在90°时达到最大值96.1%;试样的硬度和抗拉强度均先升高后降低,在45°时达到最大值,硬度为393 HV,抗拉强度为1 288 MPa;试样表面粗糙度Ra也呈先增大后减小的趋势,在0°时达到最小值8.77μm,在30°时达到最大值19.55μm。     

Influence of Microstructure on High Temperature Solid Particle Erosion Behaviour of Ti–6Al–4V Alloy

The present article describes the influence of microstructure i.e. lamellar, bimodal and equiaxed on solid particle erosion behaviour of Ti–6AL–4V alloy at service exposed temperature i.e. 400 °C. Erosion tests have been carried out using an air jet type test rig and Taguchi’s experimental design. From erosion test, it has been observed that impact velocity is the most significant controlling factor influencing the erosion of Ti–6Al–4V alloy followed by impingement angle, size of erodent and microstructural variation.The results indicated that erosion rate of Ti–6Al–4V alloy was less in bimodal microstructure followed by equiaxed and lamellar microstructure.     

Effects of Solidification Conditions on Grain Refinement Capacity of TiC in Directionally Solidified Ti6Al4V Alloy

In this study, the effects of solidification conditions on the grain refinement capacity of heterogeneous nuclei TiC in directionally solidified Ti6Al4V alloy were investigated using experimental and numerical approaches. Ti6Al4V powder with and without TiC particles in a Ti6Al4V sheath was melted and directionally solidified at various solidification rates via the floating zone melting method. In addition, by using the phase field method, the microstructural evolution of directionally solidified Ti6Al4V was simulated by varying the temperature gradient G and solidification rate V. As the solidification rate increased, the increment of the prior β grain number by TiC addition also increased. There are two reasons for this: first, the amount of residual potent heterogeneous nuclei TiC is larger. Second, the amount of TiC particles that can nucleate becomes larger. This is because increasing the constitutional undercooling ΔT_c leads to the activation of a smaller radius of heterogeneous nuclei and a higher nucleation probability from each radius. At a cooling rate R higher than that in the floating zone melting experiment (R = 3 to 1000 K/s), the maximum degree of constitutional undercooling ΔT_c,Max has a peak value, which suggests that constitutional undercooling ΔT_c has a smaller contribution at higher cooling rates, such as those that occur during electron beam melting (EBM), including laser powder bed fusion (LPBF).

     

粉末冶金Ti6Al4V合金的研究

采用Ti粉、AlV中间合金粉,通过模压和真空烧结制备了Ti6Al4V合金,并通过随后的锻造和热处理来改变其组织和性能.通过金相显微镜、X射线衍射(XRD)仪、扫描电镜(SEM)及力学性能检测等分析手段,系统研究了压制压力对Ti6Al4V烧结体密度的影响,以及试样状态(烧结态及烧结淬火态)、锻造温度、淬火温度及时效温度等工艺参数对粉末冶金Ti6Al4V合金组织和性能的影响.结果表明:通过模压和烧结可制备出相对密度达97.4%的Ti6Al4V合金;Ti6Al4V烧结态及烧结淬火态合金经过锻造后,相对密度接近100%;通过不同热处理工艺得到不同组织和性能,能获得等轴组织,其α晶粒尺寸在5μm左右.     

线性回归法建立Ti6Al4V合金超塑变形本构关系

材料的本构关系是描述材料变形的基本信息,是联系材料塑性变形过程中流动应力和变形工艺参数的桥梁.本文通过在Gleeble1500热模拟试验机上,在温度860～950 ℃、应变速率0.0005～0.05 s-1范围内对Ti6Al4V(w[Al]=6%,w[V]=4%)合金进行超塑性等温压缩变形试验,分析了压缩变形过程中的变形行为.结果表明,Ti6Al4V合金在超塑性压缩变形中,随着温度的升高或应变速率的降低,材料的流变应力显著降低,动态再结晶是其主要的软化机制.在实验数据的基础上采用多元线性回归方法建立了反映流动应力与各影响因素间关系的本构方程.     

基体梯度降温对钛合金表面沉积金刚石薄膜的影响

采用热丝化学气相沉积法(HFCVD)在钛合金(Ti6Al4V)表面沉积金刚石薄膜,研究基体温度对金刚石形核的影响,及梯度降温CVD技术(即高温梯度降温形核-低温生长)对所得金刚石薄膜样品的物相组成、表面形貌和附着性能的影响。利用扫描电镜(SEM)、激光拉曼光谱(Raman)和维氏硬度仪分析薄膜的形貌、结构、成分和附着性能。结果表明:基体温度较高时,基体表面钛原子和活性碳原子具有更高的能量,更利于活性碳原子向基体的扩散,促进碳化钛的形成,最终延长金刚石的孵化期;采用高温形核-低温生长的梯度降温法可以在550~600℃下沉积质量良好的金刚石薄膜;基体温度在30 min内从800℃逐渐降温至550℃后再生长7 h,所得金刚石薄膜样品具有较好的附着性能。