熔炼功率对EIGA制备Ti-6Al-4V合金粉末特性的影响

基于电极感应熔炼惰性气体雾化(EIGA)技术制备Ti-6Al-4V钛合金粉末,采用激光粒度仪、扫描电镜(SEM)等测试分析手段研究熔炼功率对粉末粒径分布及形貌的影响规律。结果表明:在实验参数范围内,EIGA技术制备的Ti-6Al-4V钛合金粉末,具有粒径细小、流动性好、松装密度大、球形度高等特点,适用于3D打印技术;随着熔炼功率的增大,粉末的中值粒径存在细化的趋势,但当功率增大到33 kW时,粉末中值粒径相对增大;球形度下降,并且粉末中卫星球比例也明显增大。从粉末松装密度、流动性、球形度、粒度、形貌等综合因素考虑,适合Ti-6Al-4V钛合金粉末制备的熔炼功率为30 kW。     

EIGA法制备激光3D打印用TA15钛合金粉末

采用电极感应熔炼气雾化(EIGA)法制备了激光3D打印用TA15钛合金粉末,研究了熔炼功率对粉末收得率、粒径分布、粉末形貌、松装密度和流动性等特征的影响。结果表明,随着感应熔炼功率增大,粉末收得率和平均粒径减小,当熔炼功率为65kW时,粉末收得率超过62%,中值粒径D_(50)小于100μm,松装密度为2.731g/cm3,流动性为22.46s/50g。对粒径50~180μm的粉末采用激光3D打印,激光直接沉积成形的TA15钛合金样品表面无宏观裂纹和气孔等缺陷,金相组织为细晶网篮组织,制备的TA15钛合金粉末具有良好的可打印性。     

EIGA法制备TA17合金粉末的激光增材适应性研究

TA17合金是一种已在核电领域实现工程应用的高性能钛合金,而关于TA17合金粉末性能及其增材制造样件性能相关的研究报道均较为匮乏.本文利用电极感应熔炼气雾化法(EIGA)法制备了10 ～ 61 μm和106 ～160μm两种粒度规格的TA17合金粉末,并分别对其在激光选区熔化(SLM)和激光立体成型(LSF)两种技术下的成形组织与力学性能进行了研究,对该粉末在不同工艺条件下的激光增材适应性进行了分析.结果 表明:EIGA法制备的TA17合金粉末具有良好的表面形貌和球形度;利用10 ～61 μm粒度规格粉末制备的SLM试件以及利用106 ～160 μm粒度规格粉末制备的LSF试件均具有均匀的微观组织,未见孔洞等明显缺陷,且其室温拉伸强度超过680 MPa,冲击吸收功KU2超过71 J,激光增材试验件的组织及力学性能均满足TA17合金锻件标准要求.本研究为TA17合金增材制造技术在核动力领域的应用奠定了基础.     

电极感应熔炼气雾化法制备粉末冶金增材制造原材料金属粉末的研究综述

电极感应熔炼气雾化(Electrode induction melting gas atomization, EIGA)是一种制备超洁净无夹杂物金属粉末的先进制粉技术，由于其工艺过程中不使用耐火材料并且所制备粉体具有粒径小、球形度高、无夹杂物等特点，目前已成为大规模制备粉末冶金增材制造用超洁净金属粉末的重要方法。但国内对于EIGA技术引进较晚，对其工艺设计研究还未达到德国等先进国家的水平，因此，本文综述了自1991年德国ALD公司申请专利30年以来EIGA技术的发展及工艺研究现状，对EIGA技术的优点进行了汇总，归纳了EIGA技术的机理研究脉络与技术要点，并通过纵观气雾化制粉的发展历程对EIGA技术的未来发展做了展望，为粉末冶金和增材制造原材料粉末的制备提供了参考。     

等离子旋转电极雾化法制备高品质Ti-6.5Al-1.4Si-2Zr-0.5Mo-2Sn合金粉末

旨在制备高品质Ti-6.5Al-1.4Si-2Zr-0.5Mo-2Sn粉末,为后续粉末高温钛合金构件的制备奠定基础。首先采用真空自耗电弧熔炼(VAR)技术制备Ti-6.5Al-1.4Si-2Zr-0.5Mo-2Sn合金铸锭,对铸锭进行化学成分检测,并分析其合金元素损耗、成分均匀性以及显微组织和物相组成。利用制得棒料,采用等离子旋转电极雾化法(PREP),选取不同转速制备得到钛合金粉末,将粉末筛分成不同粒度范围。研究了棒料转速与粉末理化性能间的关系。采用X射线衍射分析仪(XRD)、扫描电镜(SEM)、金相显微镜(OM)分别分析了粉末的物相组成、形貌和微观组织。研究表明:通过独特的压制电极设计,可制得成分均匀、元素损耗小的钛合金铸锭,且各合金元素含量满足国标的要求。铸锭微观组织为层片状结构,基体中存在少量大小不均的Ti5Si3硅化物相。PREP法制得的钛合金粉末呈正态分布,且球形度好,无空心球和卫星球。随着转速增加,小颗粒粉末占比增加,大颗粒粉末占比大幅度降低。粉末颗粒以胞状组织为主,存在少量的枝晶。合金粉末主要由α′马氏体相组成。相比合金铸锭,粉末中各合金元素略有损耗,O元素质量分数小于0.1%,有利于制得高性能的粉末钛合金。     

选区激光熔化用高强合金钢粉末制备及其成形性研究

目的 研究真空感应熔炼气雾化法(VIGA)制备球形24CrNiMoY高强钢粉末并验证其激光3D打印性能。方法 阐明不同雾化气压对粉末形貌、流动性等粉体特征的影响,分析选区激光熔化技术快速成形合金钢样品的微观组织和力学性能。结果 在9.0 MPa雾化气压下制备的粉末球形度最佳,粉末松装密度达到4.89 g/cm³,流动性能为21.4 s/(50 g),粉末含氧量0.023%,空心球率＜3%,粉末的微观组织主要是马氏体。经过激光工艺参数调控,SLM成形合金钢试样的激光熔池内存在两个明显不同的微区:激光熔化区(LMZ)和热影响区(HAZ)。LMZ主要是马氏体组织,HAZ主要为下贝氏体组织。合金钢试样的平均显微硬度为(402±5.7)HV0.2,其抗拉强度达到(1 246±12) MPa,断后伸长率为(11.6±0.5)%。结论 VIGA方法制备的 24CrNiMoY高强钢粉末满足SLM技术使用要求,具有良好的激光3D打印成形性。     

高温钛合金Ti-60粉末的制备和表征

采用感应熔炼气体雾化法制备了掺杂稀土Nd的高温钛合金Ti-60粉末。结果表明,在制备过程中合金元素几乎没有烧损,增氧量小于100×10~(-6);粉末的平均粒度(d_(50))约为100μm,满足正态分布,雾化气体的压力增大则粉末的粒度减小;粉末的形貌大多呈球形,只有少量的形状不规则;部分粉末是空心的,其比例随着粉末粒度的增加而增大;粉末表面有明显的凝固特征,具有清晰的二次枝晶;随着Nd含量的增加,粉末表面富Nd稀土相的析出增加;粉末由针状α′马氏体组织构成,当真空退火温度超过700℃时马氏体开始微量分解,当温度升高到850℃时马氏体大量分解。     

一种新型的雾化方法

固体雾化是一种新型的制粉方法 ,通过改变雾化介质可以改善雾化效果。本文介绍固体雾化的理论依据及总结固体雾化的主要特征 ,研究表明在同等气体压力和流量的条件下 ,采用含有固体颗粒盐的高速气流对金属液体和合金进行雾化破碎 ,所得粉末比不含固体颗粒盐的高速气流制得的粉末 ,粒度细的多 ,粉末粒度分布窄 ,粉末冷却速度较大     

等离子旋转雾化制备航空用3D打印金属粉体材料研究

正获得高品质、低成本的球形粉体材料是满足金属3D打印技术及制备高性能金属构件的关键环节。现阶段,快速凝固制粉工艺是制备金属3D打印粉体材料的核心技术之一~([1,2])。快速凝固技术是将金属、合金熔体直接雾化制得球形粉末,或通过高压雾化介质(水或气体)的强烈冲击,或通过离心力使之破碎,高速冷却凝固实现的~([3])。目前,应用于金属3D打印粉体材料制备的快速凝固技术主要有惰性气体雾化法(AA法)、真空感应气雾化法(VIGA法)、无坩埚电极感应     

TiAl基合金感应熔炼自由液面的变化规律研究

冷坩埚感应熔炼技术提高了钛铝基合金的熔体质量.对合金熔体在该熔炼中自由液面变化的认识,增强了对熔炼过程的控制优化.对Ti48Al(原子分数)进行了冷坩埚感应熔炼实验研究,采用十字钢板烧痕法测试了自由液面形状,计算了熔体自由液面高度,获得了Ti48Al自由液面形状随功率、炉料质量或者密度的经验公式.结果表明:增加功率或减少炉料质量均使自由液面高度增大;Ti48Al比相同熔体体积纯Ti的自由液面高度增加.与纯Ti比较,TiAl基合金的密度小、电导率大,增加功率、减少炉料质量不利于TiAl基合金获得稳定的熔体自由液面.     

高温钛合金Ti-60粉末的制备和表征

采用感应熔炼气体雾化法制备了掺杂稀土Nd的高温钛合金Ti--60粉末。 结果表明, 在制备过程中合金元素几乎没有烧损, 增氧量小于100×10^-6; 粉末的平均粒度(d₅₀)约为100 μm, 满足正态分布, 雾化气体的压力增大则粉末的粒度减小; 粉末的形貌大多呈球形, 只有少量的形状不规则; 部分粉末是空心的, 其比例随着粉末粒度的增加而增大; 粉末表面有明显的凝固特征, 具有清晰的二次枝晶; 随着Nd含量的增加, 粉末表面富Nd稀土相的析出增加; 粉末由针状 α' 马氏体组织构成, 当真空退火温度超过700℃时马氏体开始微量分解, 当温度升高到850℃时马氏体大量分解。     

液体金属和合金的固-气两相流雾化的研究

采用铁粉作为固体雾化介质,研究固-气两相法的雾化工艺。通过对Al-30％Si的研究,结果表明:固-气两相流雾化制粉与普通气体雾化相比,能有效减小雾化粉末的粒度,提高细粉收得率,普通气体雾化制粉得到的粉末平均颗粒尺寸为150μm,固-气两相流雾化粉末的平均颗粒尺寸为50μm;使冷却速度显著提高,达到10~4～10~5K/s,相比普通气体雾化提高了10～100倍,使Al-30％粉末的微观组织明显细化,固-气两相流能量利用率增加。     

Modification of metal surfaces by the laser melt-particle injection process

The laser melt-particle injection process was used to accomplish diverse modifications in the structure and chemistry of metal surfaces. This process consists in melting a shallow pool on the surface of a metal with a high power laser beam and injecting fine particles into the melt. In this paper we discuss wear-resisting surfaces produced by injecting TiC particles into the surfaces of 5052 aluminum and by surface alloying the same base metal with silicon. The operating conditions employed in the surface-alloying experiments were very similar to those used for carbide injection, but nearly complete dissolution of the injected silicon particles occurred during alloying while the injected carbide particles did not dissolve to any detectable degree.Previous experiments with this process have all been conducted at reduced pressure in an inert gas. The surface alloying and some of the carbide injection work described here were done at atmospheric pressure using a powder injection nozzle with inert gas shielding.     

Undercooling and supersaturation of alloying elements in rapidly solidified Al-8.5% Fe-1.2% V-1.7% Si alloy

Dispersion-strengthened Al-8.5% Fe-1.2% V-1.7% Si alloy was produced by inert gas atomization and atomized melt deposition processes. Differential scanning calorimetry was used to estimate the extent of undercooling in the alloy powders as a function of powder size and in the atomized melt-deposited alloy as a function of process parameters. The estimated undercooling was found to be a strong function of powder size and processing conditions and varied from 380–200 °C. Alloy powders of diameter greater than 180 jam did not experience any undercooling during solidification. X-ray diffraction analysis was performed to study the dependence of supersaturation of alloying elements and metastable phase formation on the extent of undercooling. When the undercooled alloy was heated to about 400 dgC, formation of Al₁₂(Fe, V)₃Si phase with b c c crystal structure from the supersaturated matrix was observed.     

Increasing the amorphous yield of {(Fe0.6Co0.4)0.75B0.2Si0.05}96Nb4 powders by hot gas atomization

The synthesis of metallic glasses requires high cooling rates leading to product size limitations of a few millimeters when using conventional casting techniques. One way to overcome these size limitations is powder metallurgy. Melt atomization and the subsequent powder processing can result in larger, amorphous components as long as no crystallization takes place during powder consolidation.An iron-based glass-forming alloy {(Fe_0.6Co_0.4)_0.75B_0.2Si_0.05}₉₆Nb₄ was formed through both ambient room and high temperature inert gas atomization at various melt flow rates (close-coupled atomization). The use of hot gas generally decreases the droplet size and hence leads to an increased cooling rate and amorphous fraction of the atomized powders.Hot gas atomization results in a lower gas consumption, a smaller gas-to-melt mass flow ratio (GMR), smaller particles and a smaller geometric standard deviation.Particles atomized in ambient temperature were fully amorphous up to a particle size fraction of 90?µm. Larger particle size fractions resulted in a higher crystalline fraction. According to the XRD and DSC analyses, hot gas atomization has only a very small influence on the cooling rate and the amorphous fraction. However, the amorphous yield is significantly increased using hot gas atomization.     

CoCrFeMnNi high‐entropy alloy powder with excellent corrosion resistance and soft magnetic property prepared by gas atomization method

To successfully fabricate high‐entropy alloys by powder metallurgy, laser cladding, or thermal sprayed method, the high‐entropy alloy powders possessing good homogeneous microstructure are very important. However, the study on the properties of the high‐entropy alloy powder has still been lacking. In this work, an equiatomic CoCrFeMnNi high‐entropy alloy powder with spherical shape was synthesized by gas atomization method. The as‐atomized CoCrFeMnNi high‐entropy alloy powder is composed of a single face‐centered cubic solid solution phase with the particle size of 34.0 μm. Furthermore, the as‐atomized powder exhibits excellent corrosion resistance in 10 % hydrochloric acid solution to 304 L stainless steel powder, and also shows an excellent soft magnetic behavior. Therefore, the gas atomization method can be used to generate other kinds of high‐entropy alloy powders for many challenging industrial applications.     

Microstructures and Mechanical Properties of Rapidly Solidified Mg-Al-Zn-MM Alloys

Mg-Al-Zn-M M （misch metal） alloy powders were manufactured by inert gas atomization and the characteristics of alloy powders were investigated.In spite of the low fluidity and easy oxidation of the magnesium melt,the spherical powder was made successfully with the improved three piece nozzle systems of gas atomization unit. It was found that most of the solidified powders with particles size of less than 50μm in diameter were single crystal and the solidification structure of rapidly solidified powders showed a typical dendritic morphology because of supercooling prior to nucleation.The spacing of secondary denrite arms was deceasing as the size of powders was decreasing.The rapidly solidified powders were consolidated by vacuum hot extrusion and the effects of misch metal addition to AZ91 on mechanical properties of extruded bars were also examined.During extrusion of the rapidly solidified powders,their dendritic structure was broken into fragments and remained as grains of about 3μm in size.The Mg-Al-Ce intermetallic compounds formed in the interdendritic regions of powders were finely broken,too.The tensile strength and ductility obtained in as-extruded Mg-9 wt pct Al-1 wt pct Zn-3 wt pct MM alloy wereσ-（T.S.） =383 MPa andε=10.6%,respectively.All of these improvements on mechanical properties were resulted from the refined microstructure and second-phase dispersions.     

Selective Laser Melting of Duplex Stainless Steel Powders: An Investigation

Selective laser melting gained substantial momentum in the recent past and quite a few alloy systems have been researched and made available for commercial use; titanium, aluminum, stainless and tool steels, cobalt chrome, and Inconel being the most popular examples. Despite the application potential, and the successful processing of powder forms by traditional powder metallurgy methods, selective laser melting of duplex stainless steels was not attempted so far. The response of a duplex stainless steel alloy to processing by selective laser melting with varying process conditions is evaluated in the current research. Experimental results ascertained that the complete cycle starting from duplex powders, consolidating into 3D forms by selective laser melting and then post-process heat treatment to bring the microstructures back to duplex forms is feasible. Within the current experimental domain, the multi-layer samples are close to 90% density and showed a maximum dimensional variation of 2–3%, while the austenite to ferrite ratio is 45:55 after the post-process heat treatment.