机械合金化及热压烧结制备Fe-Cr-Mn基超细晶奥氏体不锈钢研究

采用高能研磨诱导的机械合金化方法制备了Fe-Cr-Mn基不锈钢合金粉末;对机械合金化粉末分别进行了退火和热压烧结,分析了退火过程中的相变规律,并对热压烧结获得的奥氏体不锈钢进行了组织和耐蚀性能研究。结果表明:机械合金化获得的不锈钢合金粉由亚稳态的纳米晶铁素体构成;退火/热压烧结处理后,铁素体逐渐转变为热力学上更加稳定的奥氏体,相变温度介于498℃到730℃之间;对机械合金化16 h的合金粉末在900℃、200 MPa条件下热压烧结1h获得了Fe-Cr-Mn基奥氏体不锈钢,其平均晶粒尺寸为亚微米级且表现出高硬度和良好的耐蚀性能,其HV硬度值约为5350 MPa、自腐蚀电位和自腐蚀电流密度分别为–0.28 V和1.43×10-9 A·cm-2。     

机械合金化与热压烧结法制备Cu-Cr-Zr合金

以Cu、Cr和Zr粉末为原料,采用机械合金化法活化Cu-Cr-Zr复合粉末,然后对机械合金化后的粉末进行真空热压烧结制备Cu-Cr-Zr合金材料。利用X射线衍射仪分析机械合金化过程中粉末的物相;通过对合金抗弯强度、相对密度、导电率、显微硬度的测试和金相观察,研究了合金力学性能随温度的变化。结果表明,球磨促进了Cr和Zr在Cu中的固溶,并细化了各粉末的晶粒;随热压烧结温度的升高,其固溶度降低,提高了材料导电性,导致合金力学性能下降。     

机械合金化及放电等离子烧结制备高氮奥氏体不锈钢

采用机械合金化技术和放电等离子烧结(SPS)制备了无镍高氮奥氏体钢(0Cr17Mn11Mo3N),研究了机械合金化粉末及其SPS烧结块体的氮含量、组织结构及性能的变化规律。研究表明:随着机械合金化时间的延长,粉末的氮含量显著增加,颗粒不断细化,球磨48 h和60 h能获得氮含量高、颗粒细小、成分均匀的不锈钢粉末;经过SPS烧结后粉末中的大部分氮能够在块体中保留下来,随着烧结温度的提高,烧结块体中的氮含量降低,致密度增加,球磨48 h和60 h的高氮不锈钢粉末在1000℃烧结都能获得完全奥氏体的高氮不锈钢块体,其氮含量分别为0.98%和1.06%,致密度达到97.44%和96.79%,硬度值高达458 HV10和471 HV10,且烧结体的断口主要呈现出撕裂型的韧窝延性断裂特征。     

热压烧结工艺制备Fe3Al金属间化合物块材的显微结构和力学性能研究

采用机械合金化结合热处理工艺制备Fe3Al金属间化合物粉末,并通过热压烧结工艺制备Fe3Al金属间化合物块材.研究机械合金化和热处理工艺对所制备Fe3Al金属间化合物粉末的物相组成和显微结构的影响.并对Fe3Al金属间化合物块材的物相组成、显微结构和力学性能进行研究.采用机械合金化工艺球磨60h制备Fe-Al金属间化合物粉末;Fe-Al合金粉末经800、1000℃热处理工艺转变成Fe3Al金属间化合物粉末.研究表明,随着球磨时间的增加,Fe-Al金属间化合物粉末的颗粒尺寸逐渐减小.球磨60h得到的Fe-Al金属间化合物粉末的平均粒度为4～5 μm.经800、1000℃热处理得到的Fe3Al金属间化合物粉末的平均粒度为4～5 μm;热压烧结块材为Fe3Al金属间化合物相;热压烧结制备的Fe3Al金属间化合物块材的显微结构均匀致密;热压烧结工艺制备的Fe3Al金属间化合物块材的相对密度较高且具有较高力学性能.     

金刚石抛光用钨合金的热压烧结

为了获得适用于摩擦化学抛光单晶金刚石用的高性能W-Mo-Cr合金抛光材料,采用机械合金化法制备的微细W-Mo-Cr合金粉末为原料,研究热压烧结参数(烧结温度、压力和保温时间)对材料致密度和硬度的影响,并采用扫描电镜(SEM)对材料的显微组织进行观察。结果表明:采用机械合金化和热压固相烧结相结合的方法可以制备出高致密度、高硬度的合金材料,合金材料组织致密,平行精度良好;在烧结温度为1400℃、压力为30 MPa、保温时间为30 min的工艺条件下,所制备的W-Mo-Cr合金材料相对密度为96.49%,硬度为777.78HV。     

β-FeSi_2基热电材料的制备及其研究进展

概述了β-FeSi_2的制备方法,包括机械合金化、粉末烧结、热压烧结、激光烧结、快速凝固和自蔓延合成等,分析了各自的优缺点,并结合国内外的研究现状进行展望。     

纳米Mg2Sn增强镁基复合材料组织与性能

利用纳米Sn粉高的表面活性,通过微米Mg粉与纳米Sn粉的机械合金化高效合成了含原位纳米Mg₂Sn相的复合粉末,将所得复合粉末热压烧结,获得高性能纳米Mg₂Sn增强镁基复合材料。对比研究了不同机械合金化时间对镁基复合材料组织、性能的影响,结果表明：随着机械合金化时间的延长,由纳米Mg₂Sn相组成的团簇尺寸不断减小,分布更加均匀,烧结态Mg₂Sn/Mg复合材料的各项力学性能也得到不断提高。     

机械合金化制备304不锈钢显微组织与性能研究

通过机械合金化制备了304不锈钢粉末并在高温高压下烧结成块,对比研究了块材在固溶热处理前后的力学性能和耐腐蚀性能演化。结果表明,经过8 h棒磨之后的Fe、Cr、Ni混合粉末实现固溶并获得BCC亚稳结构,经过烧结后发生BCC向FCC转变,最终获得接近FCC单相的纳米晶结构;由于细晶强化作用,抗拉强度高达900 MPa左右。经过固溶处理后,机械合金化的304不锈钢的抗点蚀性能大幅度提高,超过了标准304不锈钢。     

纳米Mg_2Sn增强镁基复合材料的组织与性能

利用纳米Sn粉高的表面活性,通过微米Mg粉与纳米Sn粉的机械合金化高效合成了含原位纳米Mg_2Sn相的复合粉末,将所得复合粉末热压烧结,获得高性能纳米Mg_2Sn增强镁基复合材料。对比研究了不同机械合金化时间对镁基复合材料组织、性能的影响。结果表明:随着机械合金化时间的延长,由纳米Mg_2Sn相组成的团簇尺寸不断减小,分布更加均匀,烧结态Mg_2Sn/Mg复合材料的各项力学性能也得到不断提高。     

机械合金化和真空热压烧结FeCoCrNiMn高熵合金的显微组织和力学性能（英文）

采用机械合金化和热压烧结制备FeCoCrNiMn高熵合金。结果表明,采用机械合金化得到纳米晶合金粉末,粉末相结构由面心立方结构(FCC)相以及少量的体心立方结构(BCC)相和非晶相组成。热压烧结后,合金中BCC相基本消失,同时伴随着σ相和M23C6相的析出;烧结温度的升高导致析出相颗粒明显长大。随着热压烧结温度从700℃升高到1000℃,合金塑性应变从4.4%增加到38.2%,而屈服强度从1682 MPa下降到774 MPa。经800℃和900℃烧结1 h的FeCoCrNiMn高熵合金具有较好的综合力学性能。     

Formation of Fe-19 wt%Cr-9 wt%Ni Nanocrystalline Alloy with Excellent Corrosion Resistance: Phase Transition and Microstructure

In this paper, microstructure characteristics and phase transitions of Fe-19 wt%Cr-9 wt%Ni nanocrystalline alloy are comprehensively studied during the mechanical alloying and hot pressing sintering processes. Corrosion resistance of the sintered Fe-19 wt%Cr-9 wt%Ni nanocrystalline alloy samples is further analyzed. During the mechanical alloying process, Fe-19 wt%Cr-9 wt%Ni nanocrystalline alloy powders mainly composed of metastable ferrite phase are obtained after mechanical alloying for 8, 16 and 24 h, respectively. In the subsequent hot pressing sintering process, the phase transitions(from ferrite to austenite) occur from 650 to 750 °C for Fe-19 wt%Cr-9 wt%Ni alloy powders milled for 24 h. When the sintering temperature is raised to 1050 °C for 1 h, the ferrite phase has transformed into austenite phase completely, and the obtained grain size of sintered Fe-19 wt%Cr-9 wt%Ni alloy is around 40 nm. Electrochemistry test of the sintered Fe-19 wt%Cr-9 wt%Ni alloy has been operated in 0.5 mol L~(-1) H_2SO_4 solution to show the corrosion resistance properties. Results show that the sintered Fe-19 wt%Cr-9 wt%Ni alloy exhibits excellent corrosion resistance, which is proved by higher self-corrosion potential, lower self-corrosion current density and larger capacitive reactance, compared with that of commercial 304 stainless steel.     

Synthesis and Characterization of CrCuFeMnMo0.5Ti Multicomponent Alloy Bulks by Powder Metallurgy

In this study, CrCuFeMnMo_0.5Ti multicomponent alloy bulks were prepared by powder metallurgy of mechanical alloying and sintering. A simple body-centered cubic (bcc) solid solution was prepared after 40 h ball milling of the raw CrCuFeMnMo_0.5Ti metallic powder. Particles of the alloyed powder are in microsized structures, which are actually a soft agglomeration of lamellar grains with thicknesses less than 1 μm. Meanwhile, the lamellar granules are consisted of nanosized grains under rigid cold welding. The 80-h ball-milled powder was consolidated by cold pressing and subsequent sintering at 800°C. The observed main phase in the consolidated sample after milling for 80 h is still a bcc solid solution. The solidified sample of 80-h ball-milled powder exhibits a Vickers hardness of 468 HV, which is much higher than 171 HV of the counterpart prepared from the raw metallic powder.     

Microstructure and mechanical properties of FeCoCrNiMn high-entropy alloy produced by mechanical alloying and vacuum hot pressing sintering

FeCoCrNiMn high-entropy alloys were produced by mechanical alloying (MA) and vacuum hot pressing sintering (VHPS). Results showed that the nano-crystalline alloy powders were obtained by MA and the corresponding phase structures were composed of FCC matrices and low amounts of BCC and amorphous phases. After VHPS, the BCC phases almost disappeared, simultaneously with the precipitation of σ phases and M₂₃C₆ carbides. An increase of sintering temperature resulted in grain growth of the precipitated phases. As the sintering temperature was increased from 700 to 1000 °C, the strain-to-failure of the alloys rose from 4.4% to 38.2%, whereas the yield strength decreased from 1682 to 774 MPa. The bulk FeCoCrNiMn HEAs, consolidated by VHPS at 800 °C and 900 °C for 1 h, showed relatively good combination of strength and ductility.     

机械合金化联合真空热压烧结工艺制备CoCrFeNi高熵合金的力学性能和耐腐蚀性能

采用机械合金化和真空热压烧结工艺制备了CoCrFeNi高熵合金。采用X射线衍射仪、扫描电子显微镜、电感耦合等离子体发射光谱和光学显微镜对产物的相结构和微观结构进行了表征,并采用万能试验机、维氏硬度计和电化学工作站对其力学性能和耐腐蚀性能进行了研究。结果表明：与电化学还原联合热压烧结工艺以及电弧熔炼法制备的CoCrFeNi高熵合金性能相比,机械合金化联合真空热压烧结工艺制备的CoCrFeNi高熵合金具有良好的抗拉伸强度和断裂伸长率,其合金硬度是电弧熔炼法制备合金的2倍,在0.5 mol/L H₂SO₄、1 mol/L KOH和3.5%（质量分数）NaCl水溶液中,该合金具有与304不锈钢及电化学还原联合热压烧结工艺或电弧熔炼法制备的合金相当的耐腐蚀性能。     

Sintering of Al2O3–TiB2 nano-composite derived from milling assisted sol–gel method

Synthesis and sintering of an alumina /titanium diboride nano-composite have been studied as an alternative for pure titanium diboride for ceramic armor applications. Addition of TiB₂ particles to an Al₂O₃ matrix can improve its fracture toughness, hardness and flexural strength and offer advantages with respect to wear and fracture behavior. This contribution, for the first time, reports the sintering, microstructure, and properties of Al₂O₃–TiB₂ nano-composite densified with no sintering aids. Nano-composite powder was produced by combination of sol–gel and mechano-chemical methods. The densification experiments were carried out using both hot pressing and pressureless sintering routes. In the pressureless sintering route, a maximum of 92.3% of the theoretical density was achieved after sintering at 1850 °C for 2 h under vacuum. However, hot pressing at 1500 °C for 2 h under the same condition led to achieving a 99% of the theoretical density. The hot pressed Al₂O₃–TiB₂ nano-composites exhibit high Vickers hardness (16.1 GPa) and a modest indentation toughness (~ 4.2 MPa.m^1/2).     

Thermoelectric properties of the 0.05 wt.% SbI3-Doped n-Type Bi2(Te0. 95Se0. 05)3 alloy fabricated by the hot pressing method

Thermoelectric properties of the 0.05 wt.% SbI₃-doped n-type Bi₂(Te_o.95Se_o.o5)₃ alloy, fabricated by hot pressing at temperatures ranging from 350°C to 550°C, were characterized. The electron concentration of the alloy decreased as the hot pressing temperature increased due to the annealing-out of the excess Te vacancies. When hot pressed at 350°C, a figure-of-merit of 0.75x10^-3/K was obtained due to the low Seebeck coefficient of -145 μV/K and relatively high electrical resistivity of 2.05 mΩ-cm. Upon increasing the hot pressing temperature, however, the figure-of-merit was improved mainly due to the increase of the Seebeck coefficient. A maximum figure-of-merit of 2.1x10^-3/K was obtained by hot pressing at 550°C.     

Bulk amorphous Ni59Zr20Ti16Sn5 alloy fabricated by powder compaction

The possibility of fabrication of bulk amorphous Ni₅₉Zr₂₀Ti₁₆Sn₅ alloy by hot isostatic pressing of powders was investigated. The amorphous powders were obtained by ball milling of amorphous melt spun ribbon and by mechanical alloying of a mixture of powders of pure crystalline elements. Fully amorphous bulk samples were successfully obtained by hot isostatic pressing of both types of powders. However, at least 10% porosity of the sample fabricated from the ball milled ribbon was observed. Further optimisation of the compaction process needs to be performed.     

Thermoelectric properties of p-type (Bi,Sb)2Te3 alloys fabricated by the hot pressing method

P-type (Bi_0.25Sb_0.75)₂Te₃ powders were fabricated by melting/grinding and mechanical alloying processes. Thermoelectric properties of the hot-pressed (Bi_0.25Sb_0.75)₂Te₃ were characterized with the powder processing method, powder size, hot pressing temperature, and the amount of excess-Te dopant. Specimens fabricated by melting/grinding exhibited lower Seebeck coefficient, lower electrical resistivity and higher thermal conductivity, compared to the specimens prepared by mechanical alloying. 3 wt.% excess Te-doped (Bi_0.25Sb_0.75)₂ Te₃, fabricated by melting/grinding and hot pressing at 550°C, exhibited a figure-merit of 3.2 x 10^-3/K. For 1 wt.% excess Te-doped specimen prepared by mechanical alloying and hot pressing at 550°C, a figure-merit of 3.05 x 10^-3/K was obtained.     

Effect of short carbon fiber addition on pressureless densification and mechanical properties of ZrB2–SiC–Csf nanocomposite

In the present paper, ZrB₂–SiC–C_sf composites were produced by pressureless sintering method. Carbon fiber and SiC nanoparticles with different weight percentages were added to the milled ZrB₂ powder. The mixed powders were formed by hot pressing and cold isostatic press (CIP) and after the pyrolysis, were sintered at 2100 °C and 2150 °C. In order to compare the microstructure and mechanical properties of samples scanning electron microscopy (SEM) equipped with EDS spectroscopy, XRD analysis, hardness and toughness tests were used. The results show that with the increase in weight percentage of carbon fiber, the porosity increases but the hardness, fracture toughness and density decrease. On the other hand, with the increase in weight percentage of SiC nano-particles, the porosity decreases and fracture toughness, hardness and density increase. The results indicate that in an optimal percentage of both additives, the hardness and toughness increase. Additionally, with the increase in sintering temperature, the values of hardness and fracture toughness increase and porosity decreases.     

Bulk amorphous Al85Fe15 alloy and Al85Fe15-B composites with amorphous or nanocrystalline-matrix produced by consolidation of mechanically alloyed powders

An Al80Fe14B6 powder mixture was subjected to mechanical alloying. Presence of an amorphous structure in the milling product was revealed by XRD investigations. The calorimetric study showed that the amorphous phase crystallised above 370 °C. The milled Al₈₀Fe₁₄B₆ powder was consolidated under a pressure of 7.7 GPa in different conditions: at 350 °C and at 1000 °C. Besides, the mechanically alloyed amorphous Al₈₅Fe₁₅ powder was consolidated at 360 °C. The amorphous structure was retained after consolidation applied at 350 °C and 360 °C. Compaction at 1000 °C caused crystallisation of the amorphous phase and appearance of metastable nanocrystalline phases. Structural investigations revealed that both bulk Al₈₀Fe₁₄B₆ samples are composites with boron particles embedded in amorphous or nanocrystalline matrix. The hardness of the nanocrystalline-matrix composite and of the amorphous-matrix one is equal to 707 HV1 and 641 HV1 respectively, whereas that of bulk amorphous Al₈₅Fe₁₅ alloy is 504 HV1. The specific yield strength of amorphous-matrix and nanocrystalline-matrix composites, estimated using the Tabor relationship, is 625 and 650 kNm/kg respectively, while that of amorphous Al₈₅Fe₁₅ alloy is 492 kNm/kg. We also suppose that application of high pressure affected crystallisation of amorphous phase, influencing the phase composition of the products of this process.