放电等离子烧结对TiB_2/AlCoCrFeNi复合材料组织与性能的影响

采用放电等离子烧结方法(SPS),制备体积分数5%TiB_2的等摩尔AlCoCrFeNi高熵合金基复合材料。通过密度测试、X射线衍射、扫描电镜及力学性能测试等方法,研究SPS烧结温度及烧结压力对复合材料的微结构演变与力学性能影响。结果表明:随着SPS烧结温度及烧结压力的增加,复合材料的硬度及抗压强度得到明显提高。在1200℃/30MPa进行SPS烧结后,复合材料的致密度达99.6%,抗压强度达2416MPa,屈服强度达1474MPa,硬度超过470HB。烧结过程中,复合材料的基体高熵合金发生相变,1200℃及30~45MPa烧结时,复合材料由BCC,B_2,FCC,σ及TiB_2相组成。     

粉末冶金TiVNbTa难熔高熵合金的组织和力学性能

将机械合金化(MA)与放电等离子烧结(SPS)相结合制备了难熔TiVNbTa高熵合金,研究了这种合金的机械合金化过程、相组成和显微组织,以及烧结温度和O、N含量对其力学性能的影响。结果表明:机械合金化后高熵合金粉末为BCC结构,放电等离子烧结成的块体高熵合金由BCC基体和FCC析出相组成,其析出相为TiN+TiC+TiO的复合物。烧结温度为1100℃的高熵合金具有良好的综合力学性能,压缩屈服强度达到1506.3 MPa,塑性应变为33.2%。随着烧结温度的提高,合金发生了从准脆性到塑性再到脆性断裂的转变。O和N含量的提高对高熵合金强度的影响较小,但是使其塑性显著降低。     

热压烧结(FeNiCoCr)100-x Al x (x=0、5)高熵合金的微观组织及力学性能

采用低能球磨-热压烧结制备了(FeNiCoCr)_100-x Al _x (x=0、5)高熵合金,并对其进行时效处理,研究了合金的组织结构与力学性能。结果表明：烧结态及时效态合金的微观组织均由FCC相和少量BCC相构成,其中FCC相中均存在孪晶,且未添加Al的合金中孪晶比例相对较高;添加Al的合金中BCC相较高,且时效处理后出现了大量小角度晶界。时效态FeNiCoCr合金具有最佳的综合性能,其压缩真屈服强度达545 MPa,弯曲强度和断裂韧性分别为1342±20 MPa和32.5±2.0 MPa·m^1/2,优异的力学性能归因于FCC相中退火孪晶的形成以及BCC相的析出。     

SPS烧结参数对Ti3Al2Mo5Nb室温及低温力学性能的影响

目的 研究SPS烧结温度、保温时间等工艺参数对Ti3Al2Mo5Nb在不同温度下力学性能的影响规律.方法 利用放电等离子烧结(SPS)技术快速烧结,得到致密度较高的Ti3Al2Mo5Nb低温钛合金,通过设置不同的烧结温度及保温时间,结合室温及77 K低温力学性能测试,对不同参数得到的合金的室温及低温性能进行表征,探究SPS烧结过程中工艺参数对Ti3Al2Mo5Nb合金室温及低温力学性能的影响规律.结果 随着烧结温度的升高,合金的致密度、硬度逐渐提高,室温条件下的抗拉强度逐渐提高,伸长率逐渐降低,而77 K条件下合金的抗拉强度逐渐增加,伸长率先增加后减少.随着保温时间的增加,合金的致密度及硬度变化不大,无论在室温还是在77 K低温条件下,合金的强度均先减小后增加,伸长率逐渐减少.微观组织显示,随着烧结温度的增加,β相含量逐渐减少,与伸长率的变化相同,这可能是由于β相的存在促进了室温变形过程中晶界滑移及低温条件下产生孪晶;随着保温时间的增加,析出的强化相含量先减少后增加,这可能是导致合金强度变化的原因,同时β相含量减少,从而导致合金在273 K及77 K条件下的塑性均降低.结论 对低温条件下使用的钛合金而言,在50 MPa压力下,当温度为1050℃时,保温5 min得到的样品力学性能最好,过高的烧结温度及保温时间会减少合金中β相含量,降低低温塑性.     

内氧化-高速压制法制备Al_2O_3弥散强化铜合金的性能研究

以Cu-0.18%(质量分数)Al合金粉末为原料、Cu2O为氧化剂,采用内氧化法制备Al2O3弥散铜合金粉末,采用高速压制(HVC)对粉末进行成形,经氢气中960~1 080℃烧结制备弥散强化铜合金,研究合金粉末的HVC成形效果和烧结温度对合金致密度、硬度、导电率和压缩强度等性能的影响。结果表明,HVC成形Al2O3弥散铜合金粉能获得良好的成形效果,压坯密度达到8.71 g/cm3(98.4%致密度)。与压坯相比,烧结后合金的致密度并无明显变化,但其导电率显著提升,硬度有所降低,压缩强度升高。随烧结温度的升高,合金的导电率有所升高,硬度略有降低,压缩强度基本保持恒定。经1 040~1 080℃烧结制备合金的导电率、硬度分别达到80%IACS和77 HRB以上,压缩强度达到450 MPa,能基本满足点焊电极的实际应用需求。     

氢化辅助Ti-Zr-Ta合金的制备及其性能EI

Ti-Zr-Ta难熔合金具有优良的力学性能和冲击释能特性,在含能结构材料领域展现出良好的应用前景。Ti-Zr-Ta合金目前主要通过熔炼工艺制备,但其组元均为高熔点金属,熔铸成形的方法难以制备出组织结构均匀的大尺寸部件。基于此,本工作采用氢化脱氢法预先制备Ti-Zr-Ta难熔合金粉末,并利用真空热压工艺烧结成型,在此基础上,对烧结态Ti-Zr-Ta合金的组织结构、力学性能和冲击释能特性进行了研究。结果表明:氢化脱氢法制得的Ti-Zr-Ta合金粉末平均粒径为9.4μm,由BCC1,BCC2,HCP三相组成;在1300℃的烧结温度下制备得到的Ti-Zr-Ta合金密度为7.34 g/cm^(3),基本实现了全致密化,合金主要由BCC1和BCC2两相组成,准静态压缩强度和断裂应变分别为1637 MPa和6.4%,呈脆性断裂特征。在弹道枪实验中,5.6 g烧结态Ti-Zr-Ta合金以1493 m/s的速度击穿靶板后,在27 L密闭靶箱内产生的峰值超压达到0.195 MPa,显示出较为优异的冲击释能特性,其释能主要来源于合金弹丸高速撞击产生细小碎片的氧化反应。     

氢化辅助Ti-Zr-Ta合金的制备及其性能EI北大核心

Ti-Zr-Ta难熔合金具有优良的力学性能和冲击释能特性,在含能结构材料领域展现出良好的应用前景。Ti-Zr-Ta合金目前主要通过熔炼工艺制备,但其组元均为高熔点金属,熔铸成形的方法难以制备出组织结构均匀的大尺寸部件。基于此,本工作采用氢化脱氢法预先制备Ti-Zr-Ta难熔合金粉末,并利用真空热压工艺烧结成型,在此基础上,对烧结态Ti-Zr-Ta合金的组织结构、力学性能和冲击释能特性进行了研究。结果表明:氢化脱氢法制得的Ti-Zr-Ta合金粉末平均粒径为9.4μm,由BCC1,BCC2,HCP三相组成;在1300℃的烧结温度下制备得到的Ti-Zr-Ta合金密度为7.34 g/cm^(3),基本实现了全致密化,合金主要由BCC1和BCC2两相组成,准静态压缩强度和断裂应变分别为1637 MPa和6.4%,呈脆性断裂特征。在弹道枪实验中,5.6 g烧结态Ti-Zr-Ta合金以1493 m/s的速度击穿靶板后,在27 L密闭靶箱内产生的峰值超压达到0.195 MPa,显示出较为优异的冲击释能特性,其释能主要来源于合金弹丸高速撞击产生细小碎片的氧化反应。     

3D打印CoCrFeMnNi高熵合金的微观组织、室温及低温力学性能

高熵合金由于其独特的微观结构、优异的性能及潜在的应用价值,近年来受到广泛关注,是一种重要的新型金属材料。本研究通过选区激光熔化技术制备CoCrFeMnNi高熵合金,并对所打印试样的物相组成、显微组织、常温及低温力学性能进行了系统分析与表征。通过优化打印参数,最终得到了具有高相对致密度、优异的常温及低温拉伸性能的试样,其抗拉强度分别达到647 MPa (298 K)和893.8 MPa (77 K)。本研究验证了选区激光熔化制备的CoCrFeMnNi高熵合金的强度和塑性均随着温度的降低而升高。     

氢化辅助Ti-Zr-Ta合金的制备及其性能

Ti-Zr-Ta难熔合金具有优良的力学性能和冲击释能特性，在含能结构材料领域展现出良好的应用前景。Ti-Zr-Ta合金目前主要通过熔炼工艺制备，但其组元均为高熔点金属，熔铸成形的方法难以制备出组织结构均匀的大尺寸部件。基于此，本工作采用氢化脱氢法预先制备Ti-Zr-Ta难熔合金粉末，并利用真空热压工艺烧结成型，在此基础上，对烧结态Ti-Zr-Ta合金的组织结构、力学性能和冲击释能特性进行了研究。结果表明：氢化脱氢法制得的Ti-Zr-Ta合金粉末平均粒径为9.4μm,由BCC1,BCC2,HCP三相组成；在1300℃的烧结温度下制备得到的Ti-Zr-Ta合金密度为7.34 g/cm³,基本实现了全致密化，合金主要由BCC1和BCC2两相组成，准静态压缩强度和断裂应变分别为1637 MPa和6.4%,呈脆性断裂特征。在弹道枪实验中，5.6 g烧结态Ti-Zr-Ta合金以1493 m/s的速度击穿靶板后，在27 L密闭靶箱内产生的峰值超压达到0.195 MPa,显示出较为优异的冲击释能特性，其释能主要来源于合金弹丸高速撞击产生细小碎片的氧化反应。     

机械合金化方法制备AlxCoCrCu0.5FeNi高熵合金组织结构和性能研究

采用机械合金化和真空热压烧结方法制备了Al_xCoCrCu_(0.5)FeNi高熵合金,研究Al含量对合金系的晶体结构、显微组织、硬度、压缩性能以及摩擦磨损行为的影响。球磨60h和真空热压烧结后的晶体结构均为FCC和BCC双相结构,但相对含量发生变化。Al含量的增加使合金塑性降低,硬度和强度增大,低Al含量的Al_0、Al_(0.5)合金塑性好,强度低,压缩量高达30%和25.6%;高Al含量的Al_(1.0)、Al_(1.5)合金塑性较差,强度高,压缩强度达到1855MPa和2083 MPa,原子半径大的Al含量增加造成严重的晶格畸变,使固溶强化效应增加是合金硬度和强度升高的主要原因。随着Al含量的增加,合金的断裂方式由韧性断裂向脆性断裂转变。合金的耐磨性与硬度呈正相关关系,Al_0、Al_(0.5)、Al_(1.0)的磨损机制为黏着磨损与磨粒磨损,Al_(1.5)合金则为磨粒磨损。     

Microstructure and mechanical properties of ultra-fine grained MoNbTaTiV refractory high-entropy alloy fabricated by spark plasma sintering

The MoNbTaTiV refractory high-entropy alloy(RHEA) with ultra-fine grains and homogeneous microstructure was successfully fabricated by mechanical alloying(MA) and spark plasma sintering(SPS).The microstructural evolutions,mechanical properties and strengthening mechanisms of the alloys were systematically investigated.The nanocrystalline mechanically alloyed powders with simple bodycentered cubic(BCC) phase were obtained after 40 h MA process.Afterward,the powders were sintered using SPS in the temperature range from 1500 ℃ to 1700 ℃.The bulk alloys were consisted of submicron scale BCC matrix and face-centered cubic(FCC) precipitation phases.The bulk alloy sintered at 1600℃ had an average grain size of 0.58 μm and an FCC precipitation phase of 0.18 μm,exhibiting outstanding micro-hardness of 542 HV,compressive yield strength of 2208 MPa,fracture strength of 3238 MPa and acceptable plastic strain of 24.9% at room temperature.The enhanced mechanical properties of the MoNbTaTiV RHEA fabricated by MA and SPS were mainly attributed to the grain boundary strengthening and the interstitial solid solution strengthening.It is expectable that the MA and SPS processes are the promising methods to synthesize ultra-fine grains and homogenous microstructural RHEA with excellent mechanical properties.     

Fabrication and properties of nanocrystalline Co0.5FeNiCrTi0.5 high entropy alloy by MA–SPS technique

Most of multi-component high entropy alloys were designed as equi-atomic or near equi-atomic and were mainly prepared by vacuum arc melting. The present paper reports synthesis of inequi-atomic Co_0.5FeNiCrTi_0.5 high entropy alloy by mechanical alloying and spark plasma sintering (MA–SPS). Alloying behavior, microstructure and properties of Co_0.5FeNiCrTi_0.5 alloy are investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and instron testing system, respectively. Both BCC and FCC crystal structure phases are observed after MA, while a FCC phase and additional sigma phase are noticed after SPS. Moreover, numerous nanostructured phases are founded in the alloy after consolidated by SPS. The alloy with a density of 99.15% after SPS exhibits excellent comprehensive mechanical properties. The yield stress, compressive strength, compression ratio and Vickers hardness of the alloy are 2.65 GPa, 2.69 GPa, 10.0% and 846 HV, respectively. The fracture mechanism of this alloy is observed as cleavage fracture and intergranular fracture.     

Superhard nanodisperse tungsten heavy alloys obtained using the methods of mechanical activation and spark plasma sintering

We have studied the structure and mechanical properties of nanodisperse tungsten-based heavy alloys of the W-Ni-Fe system. The temperature dependence of the density of compacted alloys exhibits a nonmonotonic character with a maximum that corresponds to the optimum temperature of sintering. The effect of the regime of solid-state pulsed spark plasma sintering (SPS) on the structure and mechanical properties of mechanically activated W-Ni-Fe heavy alloys has been studied. It is established that, using preliminary mechanical activation in a planetary ball mill and the subsequent high-rate SPS, it is possible to obtain superhard tungsten-based heavy alloys with mechanical properties that substantially exceed those of the analogous standard alloys.     

Excellent mechanical properties and large magnetocaloric effect of spark plasma sintered Ni-Mn-In-Co alloy

The Ni43.75Mn37.5In12.5Co6.25 alloy was obtained by using the spark plasma sintering (SPS) technique.The martensitic transformation,magnetic and mechanical properties of the SPS alloy were investigated.Key findings demonstrate that the martensitic transformation temperature of this alloy is about 10 K lower than that of the as-cast one.Both SPS and as-cast alloys show a 7 layered modulated martensite (7M) at room temperature.The compressive fracture strength and strain of the SPS alloy increase by 176.92％ and 33.33％ compared with the as-cast alloy,achieving 1440 MPa and 14％,respectively.The maximum magnetic entropy change △Sm is 17.1 J kg-1 K-1 for the SPS alloy at the magnetic field of 5 T.     

A novel high-entropy alloy with multi-scale precipitates and excellent mechanical properties fabricated by spark plasma sintering

Body-centered-cubic (BCC) high entropy alloys (HEAs) usually exhibit high strength but poor ductility. To overcome such strength-ductility trade-off, a novel (FeCr)₄₅(AlNi)₅₀Co₅ HEA was presented in this paper, which was designed and fabricated with mechanical alloying (MA) followed by spark plasma sintering (SPS), and has a heterogeneous microstructure with multi-scale precipitates. Electron microscopy characterization revealed that the sizes of the precipitates range from nano (<300 nm), sub-micron (300～800 nm) to micron (>1 μm). The bulk HEA exhibits excellent mechanical properties, of which the compressive yield strength, fracture strength, and plasticity at room temperature can reach 1508 MPa, 3106 MPa and 30.4 %, respectively, which are much higher than that of most HEAs prepared by Powder Metallurgy reported in the literatures, suggesting that the HEA developed is highly promising for engineering applications. The excellent mechanical properties of the bulk HEA can be attributed to that the multi-scale precipitates are fully coherent with the matrix, which could reduce the misfit strain at the interface, and relieve the stress concentration during deformation.     

基于制备钨钼复合靶材的SPS烧结连接EI北大核心CSCD

采用放电等离子烧结(SPS)制备钨(W)和钛锆钼(TZM)连接件。通过高能球磨和调节温度烧结出高致密度纯W块体,相对密度可达97.0%以上。在制备的纯W块体表面铺置TZM合金粉末,烧结TZM的同时对W和TZM进行连接,实现了异种金属块体与粉末的一步烧结连接。研究烧结温度和降温速率对W/TZM合金接头的微观组织和力学性能的影响。结果表明:W与TZM结合良好,烧结温度在1400~1600℃范围内时,W/TZM接头的剪切强度随烧结温度的升高而增大;在相同烧结温度下,采用快速冷却方式获得的接头剪切强度高于缓慢冷却接头的;当烧结温度为1600℃并采取快速冷却降温时,W/TZM接头的剪切强度达到最大,为159.7 MPa。     

制备工艺对n型Bi_2Te_3基材料热电性能和抗压强度的影响

以商用区熔(ZM)n型Bi2Te3基材料为原料,采用简单研磨结合放电等离子烧结技术(ZM+SPS)和熔体旋甩(MS)结合放电等离子烧结技术(MS+SPS)制备了n型Bi2Te3基块体热电材料.对三种不同工艺制备出样品的微结构、热电性能和力学性能进行了研究.FESEM微结构表征结果表明:区熔样品的晶粒粗大,有较强的取向性;经SPS烧结后,晶粒细化,取向性大为降低;而区熔样品经MS+SPS后,晶粒得到进一步细化,且没有明显的取向性.对三组样品进行的热电性能和抗压强度测试,结果表明:区熔原料最大ZT值为0.72(430K),抗压强度仅为40MPa;经SPS后,样品的最大ZT值为0.68(440K),抗压强度为110MPa,相比区熔样品提高了175%;MS+SPS样品的最大ZT值为0.96(320K),其室温ZT值相比区熔样品提高了64%,抗压强度相比区熔样品提高了400%,达到200MPa.     

Microstructure characteristic, mechanical properties and sintering mechanism of nanocrystalline copper obtained by SPS process

Nano-sized copper powder with an average size of 50 nm fabricated by chemical reduction method of hydrazine hydrate was consolidated using spark plasma sintering (SPS) method. The relationship between the sintering temperature and relative density of the nanocrystalline bulk copper was studied, the microstructure and the mechanical properties were examined, and the sintering mechanism was discussed. It was concluded that the nanocrystalline copper with a relative density greater than 99% and the yield strength of nearly 650 MPa could be fabricated by SPS process with the holding pressure of 600 MPa, sintering temperature of 350 °C, holding time of 5 min, and heating rate of 100 °C/min. Both refinement of the grains and formation of the extensive nanoscale twins in the NC bulk copper are the main factors to strengthen the metal.