A yttrium-containing high-temperature titanium alloy additively manufactured by selective electron beam melting

A yttrium-containing high-temperature titanium alloy(Ti-6Al-2.7Sn-4Zr-0.4Mo-0.45Si-0.1Y, mass fraction, %) has been additively manufactured using selective electron beam melting(SEBM). The resulting microstructure and textures were studied using scanning electron microscopy(SEM), transmission electron microscopy(TEM), X-ray diffraction(XRD) and electron backscattered diffraction(EBSD) and compared with the conventionally manufactured form. A notable distinct difference of microstructures is that additive manufacturing by SEBM enables homogeneous precipitation of fine Y2O3 dispersoids in the size range of 50-250 nm throughout the as-fabricated alloy, despite the presence of just trace levels of oxygen(7×10-4, mass fraction) and yttrium(10-3, mass fraction) in the alloy. In contrast, the conventionally manufactured alloy shows inhomogeneously distributed coarse Y2O3 precipitates, including cracked or debonded Y2O3 particles.

Mechanical properties of TiAl fabricated by electron beam melting-A review

As a typical intermetallic material,TiAl is inevitably difficult to process by conventional methods.Additive manufacturing(AM)has recently become a new option for making net-shape TiAl components.Among all AM methods,electron beam melting(EBM)shows the potential to make TiAl components with good mechanical properties and is used for low pressure turbine blades.The mechanical properties,including tensile and compression properties,fracture toughness,fatigue and creep properties of EBM TiAl are reviewed and compared to the conventionally fabricated alloys.Results show that the tensile strength of EBM alloys is higher than cast alloys,and other properties are comparable to the cast/forged alloys.The sensitivity of mechanical properties and microstructure to EBM processing parameters is presented.Issues including layered microstructure,anisotropy in mechanical properties,and fatigue failure from defects are also reviewed.Finally,some opportunities and challenges of EBM TiAl are identified.

Influence of multiple laser shock peening treatments on the microstructure and mechanical properties of Ti-6Al-4V alloy fabricated by electron beam melting

Laser shock peening(LSP)is an attractive post-processing method to tailor surface microstructure and enhance mechanical performances of additive manufactured(AM)components.The effects of multiple LSP treatments on the microstructure and mechanical properties of Ti-6Al-4V part produced by electron beam melting(EBM),as a mature AM process,were studied in this work.Microstructure,surface topography,residual stress,and tensile performance of EBM-manufactured Ti-6Al-4V specimens were systematically analyzed subjected to different LSP treatments.The distribution of porosities in EBM sample was assessed via X-ray computed tomography.The results showed that EBM samples with two LSP treatments possessed a lower porosity value of 0.05%compared to the value of 0.08%for the untreated samples.The strength of EBM samples with two LSP treatments was remarkably raised by 12%as compared with the as-built samples.The grains ofαphase were refined in near-surface layer,and a dramatic increase in the depth and magnitude of compressive residual stress(CRS)was achieved in EBM sample with multiple LSP treatments.The grain refinement ofαphase and CRS with larger depth were responsible for the strength enhancement of EBM samples with two LSP treatments.

Effect of Melt Scan Rate on Microstructure and Macrostructure for Electron Beam Melting of Ti-6Al-4V

Microstructure and variations in porosity in Ti-6Al-4V samples built with electron beam melting (EBM) over a range of melt scan speeds, ranging from 100 mm·s-1 to 1000 mm·s-1 were examined. Microstructure was characterized by refinement of α-phase and transformation to α′-martensite. Light optical microscopy, scanning electron microscopy, and transmission electron microscopy were used to observe these phenomena, while corresponding tensile testing and associated macro and microindentation hardness measurements were used to define the microstructural variations. Relative stiffness was observed to be linearly log-log related to relative density, corresponding to ideal porosity associated with open-cellular structures.

Influence of powder oxidation on powder properties and formability in H13 hot-work steels processed by electron beam melting

The oxygen content of metal powder is decisive for the recyclability of powder.The research on the effect of oxygen content on powder properties and material formability has practical significance for economical production with additive manufacturing while preventing the waste of resources.Here,we deliberately oxidized the powder by baking at high temperature to increase the oxygen content in the powder and gave the calculation method of the oxygen content in the powder oxidation film.The majority of oxygen element was found in the oxide particles in the powder and the oxide flm on the powder surface,which did affect the flowability of the powder.It is worth noting that the increase in the oxygen content does not change the phase of H13 steel,but it can promote the molten pool flow and obtain a smoother surface.The increase in the oxygen content in the powder is not the decisive factor for the formability and defects of the printed samples.It is the combined effect of the powder deformation,the increase in the oxygen content,and the impurity pollution after repeated use,which leads to the limitation of repeated utilization of the powder.

Metal Fabrication by Additive Manufacturing Using Laser and Electron Beam Melting Technologies

Lawrence E. Murr is Mr.J Mrs. Macintosh Murehison Professor and Chairman of the Department of Metallurgical and Materials Engineering and Ph.D. Program Director in the Materials Research Technology Institute at The University of Texas at El Paso. Dr. Murr received his B.Sc. in physical science from Albright College, and his B.S.E.E. in electronics, his M.S. in engineering mechanics, and his Ph.D. in solidstate science, all from the Pennsylvania State University. Dr. Murr has published 20 books, over 750 scientific and technical articles in a wide range of research areas in materials science and engineering, environmental science and engineering, manufacturing science and engineering （especially rapid prototype/layered manufacturing）,

Microstructure and Mechanical Performance of Ti-6Al-4V Lattice Structures Manufactured via Electron Beam Melting(EBM):A Review

Electron beam melting(EBM) process is an additive manufacturing process largely used to produce complex metallic components made of high-performance materials for aerospace and medical applications.Especially,lattice structures made by Ti-6A1-4V have represented a hot topic for the industrial sectors because of having a great potential to combine lower weights and higher performances that can also be tailored by subsequent heat treatments.However,the little knowledge about the mechanical behaviour of the lattice structures is limiting their applications.The present work aims to provide a comprehensive review of the studies on the mechanical behaviour of the lattice structures made of Ti-6A1-4V.The main steps to produce an EBM part were considered as guidelines to review the literature on the lattice performance:(1) design,(2) process and(3) post-heat treatment.Thereafter,the correlation between the geometrical features of the lattice structure and their mechanical behaviour is discussed.In addition,the correlation among the mechanical performance of the lattice structures and the process precision,surface roughness and working temperature are also reviewed.An investigation on the studies about the properties of heat-treated lattice structure is also conducted.

Dynamic compressive behaviour of Ti-6Al-4V alloy processed by electron beam melting under high strain rate loading

This paper documents an investigation into the compressive deformation behaviour of electron beam melting （EBM） processing titanium alloy （Ti-6A1-4V） parts under high strain loading conditions. The dynamic compression tests were carried out at a high strain rate of over 1 × 10^3/S using the split Hopkinson pressure bar （SHPB） test system and for comparison the quasi-static tests were performed at a low strain rate of 1×10^-3/s using a numerically controlled hydraulic materials test system （MTS） testing machine at an ambient temperature. Furthermore, microstructure analysis was carried out to study the failure mechanisms on the deformed samples. The Vickers micro-hardness values of the samples were measured before and after the compression tests. The microstructures of the compressed samples were also characterized using optical microscopy. The particle size distribution and chemical composition of powder material, which might affect the mechanical properties of the specimens, were investigated. In addition, the numerical simulation using commercial explicit finite element software was employed to verify the experimental results from SHPB test system.

电子束选区熔化成形316L不锈钢的工艺研究

电子束选区熔化是一种利用电子束逐层熔化金属粉末制造三维实体零件的增材制造技术,在航空航天、医学植入体等领域有很好的应用前景。利用316L不锈钢粉末为材料,研究粉末熔化阶段电子束功率恒定、单遍扫描对成形件上表面粗糙度的影响。发现电子束功率P与扫描速度v的比值是影响上表面形貌的关键因素,随着P/v值的增加,上表面形貌由网结状变化为沟壑状,同时粉末材料的飞溅增加。研究上表面形貌随成形高度增加而演变的过程,发现形貌随高度增加不断恶化,并解释了形貌恶化的原因。提出电子束功率递增、多遍扫描的方法,先用低功率电子束使粉末材料熔化聚球但不飞溅,再用大功率电子束使材料重新熔化并充分流动、浸润。这种方法改善了成形件上表面的形貌,表面粗糙度Ra小于8μm,获得的组织均匀细密,致密度高达99.96%。相对于单遍扫描,多遍扫描不会造成主要元素的额外烧损。

电子束选区熔化成形技术研究进展

电子束选区熔化成形技术(Selective Electron Beam Melting,SEBM),是20世纪90年代中期发展起来的一类新型增材制造技术,具有能量利用率高、无反射、功率密度高、扫描速度快、真空环境无污染、低残余应力等优点,特别适合活性、难熔、脆性金属材料的直接成形,在航空航天、生物医疗、汽车、模具等领域具有广阔的应用前景。10年来,作者团队主要开展SEBM成形钛合金的研究,合金包括TC4、TA7、Ti600、Ti Ta Nb Zr、Ti Al金属间化合物等;零件包括复杂薄壁、桁架/多孔及多孔/致密复合结构零件;并且搭建了从粉末制备、设备研发到技术服务的全产业链SEBM技术平台,通过科技成果转化成立了从事SEBM技术的专业化企业——西安赛隆金属材料有限责任公司。从成形装备、成形过程缺陷形成与控制、材料组织性能和主要应用4个方面,对国内外SEBM技术的发展现状进行了综述,最后对SEBM技术的发展前景进行了展望。

线能量密度对电子束增材制造W-Ni-Fe合金致密化过程的影响

采用粉床型电子束增材制造技术制备了90W-7Ni-3Fe高比重钨基合金,研究了不同的线能量密度对合金的显微组织及致密化过程的影响。结果表明:电子束增材制造成形的90W-7Ni-3Fe合金的组织由W颗粒和Ni-Fe固溶体粘结相组成,粘结相内溶解了一定量的W,随着线能量密度的增大,粘结相的含量及其内部W的含量增大;在不同的线能量密度下合金的致密化过程略有不同:在低的线能量密度下(0. 24 J/mm),合金的致密化过程主要是钨颗粒的粘结,随着线能量密度的升高(0. 3~0. 75 J/mm),出现了W颗粒的重排和W在Ni-Fe固溶体里的溶解-析出,随着能量密度继续增大(1. 0 J/mm),出现了一定量的钨颗粒的熔化和低熔点元素Ni、Fe的挥发,且随着钨在粘结相中的含量升高,合金的固溶强化作用增强,显微硬度相应提高。

电子束选区熔化(SEBM)增材制造高温合金研究进展

高温合金具有优异的抗氧化、耐腐蚀等性能,被广泛应用于航空发动机热端部件。以激光、电子束等高能束流为热源的增材制造(additive manufacturing,AM)技术在制备复杂结构高温合金部件方面具有显著优势:不仅能缩短生产制造周期、降低研发成本,而且能够细化合金组织,提高合金力学性能。但随着高温合金中铝、钛含量的增加,γ′相体积占比增大,合金高温力学性能提升的同时也造成其可焊性差,给增材制造该类高温合金带来挑战。与激光选区熔化(selective laser melting,SLM)技术相比,电子束选区熔化(selective electron beam melting,SEBM)技术可通过粉末床预热缓解合金凝固热应力,有利于降低增材制造时的热裂倾向。针对近年来国内外SEBM技术制备镍基高温合金、钴基高温合金等合金所涉及的工艺参数、微观组织、力学性能及应用等方面进行了综述,包括作者课题组新近的成果,并指出该领域的未来发展方向。

TC4钛合金薄壁件电子束熔丝增材修复熔覆组织及性能研究

本文利用电子束熔丝增材制造系统对TC4钛合金薄壁件进行了修复试验,分析了熔覆组织及硬度分布特征。结果表明:堆积层宏观组织是由α晶粒充当晶界包裹不规则的原始β柱状晶粒组成,柱状晶贯穿了堆积层横截面,存在明显的分层现象;层带结构“明亮”部分为粗大无规则的板条马氏体,“灰暗”部分为网篮编织的细长针状马氏体;堆积层自基体向上的硬度分布呈下降趋势,“明亮”部分对应硬度有明显升跳。

粉床型电子束增材制造W-Nb合金的缺陷及显微组织

采用粉床型电子束增材制造技术(Selective electron beam melting,SEBM)制备了W-3.5Nb合金,分析了在电子束低速扫描、高速扫描、两次熔化三种熔化条件下W-3.5Nb合金的成形缺陷和显微组织。研究结果表明:W-3.5Nb合金的成形缺陷主要包括熔合不良和微裂纹,低速扫描可有效降低缺陷含量。熔合不良主要由熔池的球化和扰动导致,微裂纹主要是由凝固过程中枝晶间液相的凝固收缩引起。不同扫描速度下,熔池的凝固过程不同,合金呈现出不同的组织特点。在高速扫描时,由于扫描层间熔合不充分,合金外延生长不明显,形成细小等轴晶,没有明显的择优取向;低速扫描时,在外延生长的作用下,形成粗大的柱状晶组织,沿成形方向形成(001)方向择优取向;在单层两次熔化条件下,柱状晶特性和晶粒的择优取向减弱。

高铌TiAl合金复杂构件制造技术研究进展

受材料本征脆性的限制,高铌TiAl合金复杂构件不适于通过机械加工获得,目前主要通过近净成形制备。分析了高铌TiAl合金的强化机制,并主要从铸造和增材制造2个方面介绍了高铌TiAl合金复杂构件加工技术的发展现状。熔模铸造TiAl合金技术成熟,已经可以实现批量化生产,但目前仍存在工艺复杂、模具制作难度大、成本高的问题。增材制造技术尤其是EBM技术取得了较快发展,高铌TiAl合金复杂构件的加工问题在一定程度上得到了解决,但产品依然存在表面粗糙度大、成形精度低等问题。

国外高能束增材制造技术应用现状与最新发展

介绍了国外以激光束、电子束为热源的高能束增材制造技术研究应用现状以及最新发展,重点介绍了高能束增材制造技术在国外航空航天的应用案例,对高能束增材制造技术的未来发展进行了展望。

增材制造TiAl基合金的研究进展

TiAl基合金具有优异的高温性能,是一种极具竞争力的新型轻质高温结构材料,在汽车、军工、航空航天等领域具有广阔的发展潜力和应用前景。然而,TiAl基合金室温脆性较大,成形困难,是阻碍其发展与应用的主要瓶颈之一。增材制造基于“离散+堆积”的成形思想,以激光、电子束、电弧等作为高能热源,通过熔化丝材或者粉末,逐层堆积实现零件的近净成形,是TiAl基合金最前沿、最具潜力的成形技术。本文主要概述了激光增材制造、电子束选区熔化、电弧增材制造TiAl基合金的研究进展,并展望了增材制造TiAl基合金的研究方向。

电子束增材制造聚焦消像散控制技术研究

为解决电子束增材制造设备加工范围受限、大尺寸工件边缘加工精度下降等问题,对大偏角下电子束的散焦和像散进行研究。采用像差理论对电子束偏转过程中出现的束径增大、形状畸变现象进行分析。本研究搭建控制系统,动态调整聚焦线圈和消像散线圈的电流,即动态聚焦消像散。制作聚焦消像散校正表,使电子束在整个扫描区域内保持小束径。采用二次电子成像方法和EOG(能量梯度函数)评价函数验证校正效果。实验结果表明,动态聚焦消像散能够有效改善束斑质量,校正后电子束在12°偏转以内清晰成像,电子图像EOG值由0.81提升至1。

电子束选区熔化增材制造技术研究现状分析

增材制造(3D打印)作为一种新兴的材料成形方法,在航空航天、生物医学等领域有着广泛的应用前景。综述了电子束增材制造(3D打印)技术国内外研究现状,简述了利用电子束选区熔化技术增材制造的基本原理和国内外研究学者已经取得的部分研究成果,并展望了电子束增材制造技术的发展方向。

电子束增材制造设备及应用进展

电子束增材制造是增材制造技术的主要方向之一,它在真空中进行,具有能量利用率高、零件残余应力低等优势,在航空航天、医疗领域获得较为广泛的应用。介绍了两种电子束增材制造方法——电子束选区熔化和电子束熔丝沉积,总结了设备、电子枪、工艺、材料组织调控等方面的研究与应用进展,并对电子束增材制造技术的发展进行了展望。