放电等离子烧结的钛铝合金组织及氧化性能研究

研究了TiH2-45Al-0.2Si-5Nb未球磨和球磨两种粉末的放电等离子烧结组织特征以及经1000℃、100h高温氧化后的氧化性能.结果表明,未经球磨粉末的烧结组织由层片状TiAl和Ti3Al相组成,而经球磨粉末的烧结组织由细小的颗粒状TiAJ和Ti3Al相组成.球磨粉末的烧结组织氧化速度低于未球磨粉末的烧结组织,形成了连续的Al2O3和TiO2混合氧化物层,具有良好的高温抗氧化性.     

球磨时间对粉末冶金制备Ti35Nb2.5Sn/10HA生物复合材料微观组织的影响(英文)

采用高能机械球磨和脉冲电流活化烧结方法制备了一种新型的β-钛合金基体的Ti35Nb2.5Sn/10HA生物复合材料。研究了机械球磨不同时间的Ti35Nb2.5Sn10HA粉体以及烧结样品的微观组织。结果表明:经机械球磨8h后,粉体中的α-钛开始向β-钛转化。当球磨时间达到12h时,球磨粉体中的α-钛相完全转化为β-钛相,而且得到超细尺寸的复合粉体。用球磨12h的粉末烧结制备的复合材料具有超细晶粒结构,烧结得到的复合材料的硬度和相对密度都随着球磨时间的延长而增加。     

Microstructural control of and mechanical properties of mechanically alloyed tungsten heavy alloys

93W-5.6Ni-l.4Fe tungsten heavy alloys with controlled microstructures were fabricated by mechanically alloying of elemental powders of tungsten, nickel and iron by two different process routes. One was the full mechanical alloying of blended powders with a composition of 93W-5.6Ni-l.4Fe, and the other was the partial mechanical alloying of blended powders with a composition of 30W-56Ni-14Fe followed by blending with tungsten powders to form a final composition of 93W-5.6Ni-l.4Fe. The raw powders were consolidated by die compaction followed by solid state sintering at 1300°C for 1 hour in a hydrogen atmosphere. The solid state sintered tungsten heavy alloys were subsequently liquid phase sintered at 1445∼1485°C for 4-90 min. The two-step sintered tungsten heavy alloy using mechanically alloyed 93W-5.6Ni-l.4Fe powders showed tungsten particles of about 6-15 μm much finer than those of 40 um in a conventional liquid phase sintered tungsten heavy alloy. An inhomogeneous distribution of the solid solution matrix phase was obtained in the two-step sintered tungsten heavy alloy using partially mechanically alloyed powders. The two-step sintered tungsten heavy alloy using mechanically alloyed 93W-5.6Ni-l.4Fe powders showed larger elongation of 16% than that of 1% in the solid state sintered tungsten heavy alloy due to the increase in matrix volume fraction and decrease in W/W contiguity. Dynamic torsional tests of the two-step sintered tungsten heavy alloys showed reduced shear strain at maximum shear stress than did the sintered tungsten heavy alloys using the conventional liquid phase sintering.     

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.     

超细WC-Co硬质合金的制备与性能研究

利用高能球磨法制备纳米级WC-Co混合粉末,采用脉冲电流烧结技术进行烧结。用能谱分析仪(EDX)对球磨后的粉末进行成分分析,用X射线衍射(XRD)对比分析球磨前后WC-Co混合粉末的衍射峰变化,用透射电子显微镜(TEM)和扫描电子显微镜(SEM)对所制备的粉末及烧结材料进行了组织形貌观察,并测定了烧结试样的硬度。结果表明:随着球磨时间的延长,WC-Co纳米粉末的粒度逐渐变小,当球磨时间超过30h后获得了粒度为100nm以下的WC-Co纳米粉末。脉冲电流烧结后获得超细WC-Co硬质合金,与传统的WC-Co硬质合金相比,超细WC-Co硬质合金具有更高的硬度(HRA92.5～94)和耐磨性。另外通过实验获得了最佳的烧结工艺参数。     

Solid state and liquid phase sintering of mechanically activated W–20 wt.% Cu powder mixture

W–20 wt.% Cu powder mixture was mechanically alloyed by high-energy ball milling for various times and the effect of mechanical alloying (MA) on the sintering response of the composite compacts was investigated. The densification, microstructure, hardness and electrical conductivity after solid phase sintering (SPS) and liquid phase sintering (LPS) were examined. It was shown that the microstructure of mechanically alloyed powder profoundly influence the sintering response, i.e. a meaningful relationship between the sintering kinetics and the milling time was observed. It is suggested that MA disintegrates the W–W particle networks and increases the contribution of solid phase sintering (SPS) of nanostructured Cu and W particles on the densification. Higher hardness and conductivity were achieved by prolonged MA and SPS, indicating a lower W–W contiguity of the milled powders compared with the conventionally prepared W–Cu composite. On the other hand, depression of the melting temperature of copper up to 145 °C was noticed by affording a prolonged MA. The lower melting temperature and finer distribution of the Cu particles in the W matrix enhanced the densification during LPS and improved the homogeneity and properties of the final product.     

粉末冶金碳化物强化铌合金组织演变及其力学行为

采用机械球磨与热压烧结相结合的粉末冶金法对不同球磨时间Nb-35Ti-6Al-5Cr-8V-5C合金的粉末变形行为,微观组织结构和力学行为进行研究。结果表明:随着球磨时间的增加,Nb-35Ti-6Al-5Cr-8V-5C复合粉末中的块状金属颗粒首先变形为片状后在碰撞挤压作用下破碎成絮状,TiC粉末均匀的分布于片状金属粉末表面;Nb-35Ti-6Al-5Cr-8V-5C合金由Nbss和(Nb,Ti)C两相构成,各合金碳化物体积分数均为11%左右,Ti元素主要分布于Nbss晶界和碳化物内,Al、Cr、V元素主要分布于Nbss晶粒内,Nbss和(Nb,Ti)C相尺寸均随球磨时间增加而尺寸减小;Nbss晶粒细化及强化相碳化物弥散化导致合金的室温压缩力学性能和塑性变形能力显著提高,压缩变形后合金Nbss与碳化物具有良好的界面结合能力,但是碳化物内部存在明显的近似平行分布的裂纹;数据对比表明,粉末冶金法制备Nb-35Ti-6Al-5Cr-8V-5C合金的力学性能优于电弧熔炼法。     

双步球磨与放电等离子烧结制备细晶TiAl合金

采用双步球磨法和放电等离子烧结(SPS)技术制备细晶Ti-47Al(at%)合金,利用扫描电子显微镜(SEM)、X射线衍射(XRD)仪以及透射电子显微镜(TEM)等分析测试手段对球磨后的粉末形貌结构、相组成以及烧结块体的显微组织结构进行观察和分析。结果表明:双步球磨粉末的颗粒形状较规则,其颗粒尺寸在20~40μm之间,内部结构均匀,主要由TiAl和Ti3Al相组成。放电等离子烧结后的块体主要由主相TiAl和少量的Ti3Al相及Ti2Al相组成,随着烧结温度的升高,Ti3Al相含量有所增加。当烧结温度为1000℃时,烧结块体获得的主要是等轴晶组织,等轴晶粒尺寸大多数在100~250nm之间。当烧结温度为1100℃时,烧结块体致密、无孔洞,等轴晶粒有明显长大的现象,显微组织主要由等轴状的TiAl相和片层状的Ti3Al相组成。     

机械合金化制备N型Si80Ge20块体热电材料的微观结构与电性能的研究

本文采用球磨工艺合成了SiGe合金粉末,结合放电等离子烧结制备出了掺杂GaP与P的N型Si<,80>Ge<,20>块体合金.利用XRD、SEM等手段对球磨粉末与烧结体进行了表征,并对烧结体进行了电性能的测试.结果表明:Si、Ge粉末经球磨后可完全形成单相的SiGe合金;通过谢乐公式的计算,机械合金化的合金粉末的平均品粒...     

Impact and dynamic deformation behavior of mechanically alloyed tungsten heavy alloy

93W-5.6Ni-l.4Fe tungsten heavy alloy was fabricated by mechanical alloying process using elemental powders of tungsten, nickel and iron, followed by sintering at temperatures of 1445~1485°C under hydrogen atmosphere. The tungsten heavy alloy sintered using mechanically alloyed powders showed finer tungsten particles about 5~18 μm with high density above 99% at shorter sintering time than that fabricated by conventional liquid-phase sintering process. Charpy impact energy of mechanically alloyed tungsten heavy alloy increased with increasing the matrix volume fraction and with decreasing the W/W contiguity. The high strain rate dynamic deformation behavior of tungsten heavy alloys using torsional Kolsky bar test exhibited different fracture modes dependent on microstructure. While the brittle intergranular fracture mode was dominant when the tungsten particles were contiguously interconnected in tungsten heavy alloys solid-state sintered below 1460°C, the ductile shear fracture mode was dominant when the tungsten particles were surrounded by ductile matrix phase in tungsten heavy alloys liquid-phase sintered above 1460°C.     

粉末冶金Nb-35Ti-6Al-5Cr-8V合金组织演变及其力学行为

采用粉末冶金法对不同球磨时间的Nb-35Ti-6Al-5Cr-8V合金机械合金化粉末塑变行为,热压烧结材料的微观组织结构和力学行为进行了研究。研究结果表明：塑性良好的Nb-35Ti-6Al-5Cr-8V粉末随着球磨时间增加首先变形为大尺寸的片状、后经持续的加工硬化破碎成絮状;热压烧结能够制备微观组织可控晶粒细化的Nb-35Ti-6Al-5Cr-8V合金,合金由单一的Nbss相构成,Ti、Al、Cr、V元素固溶引起Nb晶格尺寸减小0.0685 ?;随着球磨时间增加合金晶粒明显细化进而显著提高了合金的维氏硬度和室温压缩强度,其变化符合材料硬度和强度的Hall-Petch规律。粉末冶金制备Nb-35Ti-6Al-5Cr-8V合金的各项力学性能明显优于熔铸法制备合金。     

Microstructures and mechanical properties of biocompatible Ti-42 wt.%Nb P/M alloy

Ti-42 wt. %Nb powder was prepared by high-energy mechanical milling (HEMM). The particle size distribution (PSD) of the as-milled powder has been investigated using a particle size distribution analyzer. The morphology and microstructure of the as-milled powder have been investigated by scanning electron microscopy (SEM), X-ray diffractometry (XRD), transmission electron microscopy (TEM), and differential thermal analysis (DTA). Also, the corrosion property and biocompatibility of sintered specimens comprising mixed and milled powders have been investigated. The milled powders were sintered using pulse current activated sintering (PCAS). PCAS was employed in order to provide more refined grain size and full density to Ti-42 %Nb alloy on the basis of short sintering time with pressure. The density of the sintered Ti-42 %Nb specimen fabricated using the milled powder increased with increased milling time due to high free surface area and defect density. The density of the sintered Ti-42 %Nb specimen fabricated using as-mixed powder increased with increased sintering temperature up to 950 °C. The microstructure of the sintered Ti-42 %Nb specimen fabricated using 4h-milled powder was composed of Nb-rich and Nb-poor phases that are more refined and homogeneously distributed. The mechanical properties and biocompatibility of the sintered Ti-42 %Nb specimen fabricated using milled powder were superior to those of a commercial, Ti-6wt.%Al-4wt.%V alloy.     

不同SPS烧结温度Ti-45Al-5.5(Cr,Nb,B,Ta)合金的显微组织及力学性能(英文)

采用高能球磨和放电等离子烧结(SPS)技术,制备成分为Ti-45Al-5.5(Cr,Nb,B,Ta)的TiAl合金块体,随后对TiAl合金进行热处理。研究在不同SPS烧结温度下制备的TiAl合金经过热处理后的显微组织和力学性能。结果表明:高能球磨后的合金粉末形状不规则,粉末颗粒尺寸大约为几十微米。XRD分析表明,机械球磨后的粉末由TiAl和Ti3Al两相组成;烧结后的Ti-45Al-5.5(Cr,Nb,B,Ta)合金块体主要是TiAl相,以及少量的Ti3Al和TiB2相。当烧结温度为900°C和1000°C时,合金的显微组织为双相结构,并伴随有一些细小的等轴γ晶粒和细小的针状TiB2相。当烧结温度从900°C上升到1000°C时,Ti-45Al-5.5(Cr,Nb,B,Ta)合金的显微硬度变化不大,抗压强度从1812MPa提高到2275MPa,压缩率从22.66%增加到25.59%,合金的断裂方式为穿晶断裂。     

高能球磨工艺对Ni-Cr-P粉末性能的影响

采用机械合金化方法将Ni-Cr-P粉末用行星式高能球磨机进行球磨,利用SEM、DSC、硬度仪及万能实验机分析了不同球磨时间的粉末和烧结后的试样性能。结果表明:随着球磨时间的延长,粉末的能量在球磨20h达到最高,粉末的形貌图与粉末的能量曲线形成相对应的关系。球磨20h后的试样,在800℃进行烧结,可获得与原始粉末在920℃下烧结时性能相同的试样。     

Effects of sintering conditions on mechanical properties of mechanically alloyed tungsten heavy alloys

The effects of sintering conditions on the microstructural evolution and mechanical properties of mechanically alloyed tungsten heavy alloys were investigated. W, Ni and Fe powders were mechanically alloyed in a tumbler ball mill at a milling speed of 75 rpm, ball-to-powder ratio of 20∶1 and ball filling ratio of 15%. The mechanically alloyed powders were compacted and solid-state sintered at a temperature of 1300°C for 1 hour in a hydrogen atmosphere. The solid-state sintered tungsten heavy alloy was subsequently liquid-phase sintered at 1470°C with varying sintering times from 4 min to 90 min. The solid-state sintered tungsten heavy alloy showed fine tungsten particles of 3 μm in diameter and high relative density above 99%. The volume fraction of the W-Ni-Fe matrix phase was measured, as 11% and tungsten/tungsten contiguity was 0.74 in solid-state sintered tungsten heavy alloys. Mechanically alloyed and two-step sintered tungsten heavy alloys showed tungsten particles of 6–15 μm and a volume fraction of the W-Ni-Fe matrix phase of 16% and tungsten/tungsten contiguity of 0.40. The solid-state sintered tungsten heavy alloy exhibited a yield strength of about 1100 MPa due to its finer tungsten particles, while it showed low elongation and impact energy due to its large tungsten/tungsten contiguity. The yield strength of two-step sintered tungsten heavy alloys increased with the decreasing of tungsten particle size and volume fraction of the W-Ni-Fe matrix. This article is based on a presentation made in “The 4th International Conference on Fracture and Strength of Solid”, held at POSTECH, Pohang, Korea, August 16–18, 2000 under the auspices of Far East and Ocean Fracture Society (FEOFS)et al.     

机械合金化W-Ti粉末的烧结特性

用高能球磨法制备了W-Ti预合金粉末,研究了纳米晶W-Ti粉末的真空烧结致密化和显微组织演化现象以及热处理时组织形貌的变化,并与未球磨粉末的烧结试样进行了比较。结果表明,提高烧结温度有利于提高相对密度;1500℃,2 h为最佳烧结工艺。机械合金化导致粉末内晶粒纳米化,形成成分不均的固溶体W-Ti粉末,使真空烧结后的显微组织结构明显细化,相对密度显著提高;扩散退火后能够形成成分较均匀的W-Ti固溶体。     

Influence of Mixing Technique on the Mechanical Properties and Structural Evolution of Al-NiAl Composites

Fabrication and processing of 99.7% purity aluminum powder reinforced with 0, 5, 10% volume fractions NiAl intermetallic metal matrix composites were conducted. The mechanically alloyed nanostructured NiAl was mixed by both regular and high energy ball milling techniques. Powders of NiAl employed for reinforcement were milled for 18 and 31 h, and therefore denoted as NiAl18 and NiAl31, respectively. The mixed powders were consolidated via a combination of cold pressing followed by hot extrusion at 480 °C for 1 h at a reduction ratio 4:1. Hardness, tensile properties, and fracture behavior of the extruded composite powders were evaluated. Structural evolution of the milled composite powders was investigated before and after extrusion using optical microscopy, field emission scanning, and transmission electron microscopy. In addition, particle type identification was carried out via energy dispersive x-ray analysis. Introducing NiAl31 (0.8 µm) enhanced the mechanical properties of the composites compared to NiAl18 (1.0 µm). Moreover, powders milling enhanced the tensile properties post hot extrusion compared to the mixed conditions due to the enhanced reinforcement distribution and bonding with the Al matrices. Hot extruded milled composite powders of Al reinforced with 10% NiAl31 produced nanostructured high-angle grain boundary structure <200 nm.     

机械合金化制备Fe-10%Ni合金研究

采用纯Fe粉和Ni粉利用高能卧式搅拌球磨机制备了Fe-10%Ni(质量分数,下同)合金,利用X射线衍射(XRD)、扫描电子显微镜(SEM)、差热分析(DTA)研究了球磨粉末的相组成、形貌和热稳定性,并对其热压烧结的块材进行了组织分析与性能测试。结果表明,在球磨机转速400 r/min,球料比20:1条件下,球磨8 h后,Ni原子完全固溶在Fe原子晶格中,形成体心立方结构Fe(Ni)过饱和固溶体,延长时间到16 h,球磨粉末颗粒尺寸更均匀细小,但仍为体心立方Fe(Ni)固溶体。对球磨16 h的合金粉末在500~800℃进行退火处理,发现粉末结构稳定,仍为体心立方Fe(Ni)固溶体。对球磨16 h的合金粉末进行热压烧结,发现950℃下烧结块材中出现少量fcc结构的Fe(Ni)固溶体相,而继续在970℃复烧后则完全转变为面心立方结构的Fe(Ni),但950℃热压烧结块材的强度和延伸率高于970℃复烧的块材,原因在于无压复烧块材中产生氧化物和孔洞。     

Fabrication of mechanically alloyed Ti-Ni-Cu powders and damping properties of Al/Ti-Ni-cu sintered materials

The microstructure and phase transformation of mechanically alloyed Ti-(50-x)Ni-xCu powders added to an aluminium matrix to enhance their damping properties were studied. Four compositions between 5 and 20 at.%Cu intermetallic compounds were selected to control the fraction of the martensite phase of Ti-Ni-Cu. Mechanically alloyed Ti-Ni-Cu powders were heat-treated in a vacuum of 10⁶ torr for crystallization. Mechanically alloyed Ti-Ni-Cu powders were milled with Al, swaged at room temperature and rolled at 450°C. After mechanical alloying for 10 hours. The Ti, Ni and Cu elements were completely alloyed and an amorphous phase was formed. The amorphous phase was crystallized to martensite (B19’) and austenite (B2) after heat treatment for 1 hour at a temperature of 850°C, and a Fe₂Ti intermetallic compound was partially formed. As the Cu contents increased the austenite phase fraction increased. The specific damping capacity (SDC) of Al/TiNiCu composite was higher than that of the Al/TiNi composite or native aluminium.     

Sintering of a nano-crystalline tungsten heavy alloy powder

A nano-crystalline Tungsten heavy alloy powder was obtained by mechanical alloying of elemental powders in a jar mill with a high ball to powder ratio. The chemical composition of the primary powder was 93 W-4.9Ni-2.1Fe (wt%). The mechanically alloyed powder had 22 nm sized tungsten crystallites distributed in an amorphous nickel base phase. Mechanical alloying reduced particle size of powders and also yielded to more uniform particles size distribution. Sintering behavior and microstructural development of that powder were studied and compared with a conventionally mixed powder. Mechanically stored energy and better distribution of primary elements in Nano-crystalline powder had decreased motivation energy of sintering and that powders showed more densification at relatively lower sintering temperatures. Sintering at low temperatures can depress grain growth during sintering and provide desirable properties. A transient intermetallic phase was formed in the nano-crystalline powder during sintering that has not been seen in conventionally mixed powders.