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1.
A surface composite layer reinforced with TiB2 particles was produced on copper by use of the laser remelting in situ synthesis. The microstructure, electrical conductivity,
and sliding wear behavior of the in situ Cu-TiB2 composite were investigated. The experimental results show that the size of reinforcing TiB2 particles is about 800 nm and the microhardness of composite layer reaches HV 210. Although the electrical conductivity of
the composite layer is reduced with increasing TiB2 volume fraction, the decrease of the integrated conductivity of the samples containing composite layer and copper substrate
is insignificant. The wear resistance of composite layer is 10 times better than that of the copper sample. 相似文献
2.
The Oxidation of TiB2 Ceramics Containing Cr and Fe 总被引:5,自引:0,他引:5
The oxidation behavior of TiB2, TiB2–0.5 wt.% Cr–0.5 wt.% Fe and TiB2–1 wt.% Cr–1 wt.% Fe was studied at 800, 900, and 1000°C in static air. These ceramics oxidized rather rapidly and formed thick oxide scales. The oxidation rates of TiB2-base ceramics were comparable to TiO2 formation on pure titanium. The scale formed on TiB2 consisted of TiO2 and B2O3. For TiB–Cr–Fe ceramics, a small amount of Cr- and Fe-oxides was additionally formed. B2O3 formed during oxidation tended to evaporate because of its high vapor pressure, making oxide scales porous and fragile. The oxidation of the TiB2-base ceramics appeared to be governed by the inward transport of oxygen via the highly porous oxide scale. The oxidation resistance of TiB2–Cr–Fe ceramics was similar to or better than that of TiB2. 相似文献
3.
In the present study, the densification of Ti/TiB composites, the growth behavior ofin-situ formed TiB reinforcement, the effects of processing variables — such as reactant powder (TiB2, B4C), sintering temperature and time — on the microstructures and the mechanical properties ofin-situ processed Ti/TiB composites have been investigated. Mixtures of TiB2 or B4C powder with pure titanium powder were compacted and presintered at 700°C for 1 hr followed by sintering at 900, 1000, 1100,
1200, and 1300°C, respectively, for 3hrs. Some specimens were sintered at 1000°C for various times in order to study the formation
behavior of TiB reinforcementin-situ formed within the pure Ti matrix. TiB reinforcements were formed through different mechanisms, such as the formation of fine
TiB and the formation of coarse TiB by Ostwald ripening or the coalescence of fine TiB. There was no crystallographic relationship
between TiB reinforcement and the matrix. There were voids at the interface between the TiB reinforcement and the Ti matrix
due to the preferential growth of coarse TiB without a particular crystallographic relationship with pure Ti matrix and the
surface energy between the Ti matrix and TiB reinforcements. Therefore, the densification of Ti/TiB2 compacts was hindered by the preferential growth of coarse TiB reinforcements. The mechanical properties ofin-situ processed composites were evaluated by measuring the compressive yield strength at ambient and high temperatures. The compressive
yield strength of thein situ processed composites was higher than that of the Ti-6A1-4V alloy. It was also found that the compressive yield strength of
the composite made from TiB2 reactant powder was higher than that of the composite made from B4C at the same volume fraction of reinforcement. A crack path examination suggested that the bonding nature of interface between
matrix and reinforcement made from TiB2 reactant powder was better than that made from B4C. 相似文献
4.
Lee D. B. Kim M. H. Yang C. W. Lee S. H. Yang M. H. Kim Y. J. 《Oxidation of Metals》2001,56(3-4):215-229
The oxidation kinetics of TiAl alloys with and without (3, 5, 10 wt.%) TiB2 dispersoids were studied between 1073 and 1273 K in atmospheric air. The inert TiB2 dispersoids effectively increased the oxidation resistance of TiAl alloys. The higher the TiB2 dispersoids content, the more pronounced the effect. The oxide scale formed on TiAl–TiB2 composites was triple-layered, consisting mainly of an outer TiO2 layer, an intermediate Al2O3 layer, and an inner (TiO2+Al2O3) mixed layer. No B2O3 was observed within the oxide scale because of its high vapor pressure. A thin Ti3Al sublayer and discrete TiN particles were found at the oxide–substrate interface. During the oxidation of TiAl alloys with and without TiB2 dispersoids, titanium ions diffused outwardly to form the outer TiO2 layer, while oxygen ions transported inwardly to form the inner (TiO2+Al2O3) mixed layer. The increased oxidation resistance by the addition of TiB2 was attributed to the enhanced alumina-forming tendency and thin and dense scale formation. 相似文献
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6.
燃烧合成TiB2-Al2O3陶瓷复合粉体及其表征 总被引:3,自引:0,他引:3
采用TiB2-Al2O3-Al还原体系,通过燃烧还原技术制备了TiB2-Al2O3陶瓷复合粉体。利用XRD,XPS和SEM技术对合成粉体的相组成、化学组成及宏观组织结构进行了分析。复合粉的显微结构由TEM和HREM进行表征。结果表明,用燃烧合成法在420℃~700℃之间可制得TiB2-Al2O3陶瓷复合粉体。该粉体仅由TiB2和Al2O3两相组成,颗粒分布较均匀。由于TiB2与Al2O3间形成了结合良好的界面,颗粒间彼此能有效地抑制晶粒长大,从而使TlB2-Al2O3陶瓷复合粉的粒径减小,颗粒平均粒度在3μm~5μm之间。 相似文献
7.
Dong-Bok Lee 《Metals and Materials International》2002,8(1):69-75
The oxidation behavior of TiAl alloys containing dispersed particles of (5, 10, 15 wt.%) SiC, (3,5 wt.%) Si3N4 or (3, 5, 10 wt.%) TiB2 was studied between 800 and 1200°C in atmospheric air. The TiAl−(SiC, Si3N4) alloys oxidized to TiO2, Al2O3, and SiO2. The TiAl−TiB2 alloys oxidized to TiO2, Al2O3, and B2O3 which evaporated during oxidation. Improvement in oxidation resistance accompanied by thin, dense scale formation due to
the addition of dispersoids originated primarily from the enhanced alumina-forming tendency, improved scale adhesion by oxide
grain refinement owing to the beneficial effect of dispersoids, and the incorporation of SiO2 within the oxide scale in the case of TiAl−(SiC, Si3N4) alloys. 相似文献
8.
A relatively new generation of cermet materials, based on TiB2-Ni, has been investigated. These borides currently are being examined for industrial applications with the aim of exploiting
their excellent wear resistance. Optimization of the liquid-phase sintering process for a TilB2-Ni composition was studied. The mechanical properties of cermet materials prepared using vacuum and pressure sintering techniques
were determined. Criteria for optimal sintering conditions were established according to hardness, strength, and fracture
toughness properties. 相似文献
9.
D. B. Lee M. H. Kim S. E. Kim J. Y. Lee K. B. Park J. J. Moon S. C. Choi C. W. Yang 《Metals and Materials International》2001,7(2):143-149
TiAl alloys incorporated in (0,3,5,10) wt.% TiB2 dispersoids were manufactured via mechanical alloyingspark plasma sintering (MA-SPS), and their cyclic oxidation characteristics
were studied at 800, 900 and 1000°C in air. The cyclic oxidation resistance of the prepared TiAl-TiB2 composites effectively increased with increases in TiB2 content. The oxide scale formed consisted of an outer TiO2 layer, an intermediate Al2O3 layer, and an inner (Al2O3+TiO2) mixed layer. The scale adherence was relatively good, and much thinner oxide scales, when compared to TiB2-free TiAl alloys, were formed on the prepared composites. The incorporated TiB2 dispersoids oxidized to TiO2 and B2O3 which evaporated during oxidation. 相似文献
10.
机械合金化制备TiB2-Ni(Al)复合粉末组织结构研究 总被引:2,自引:2,他引:0
目的通过原位合成技术获得TiB_2-Ni(Al)复合粉末。方法采用机械合金化方法在不同球磨时间的条件下,制备不同体积含量的TiB_2陶瓷相增强Ni(Al)基复合粉末,其中Ni粉和Al粉的摩尔比为1:1。采用扫描电子显微镜(SEM)以及X-射线衍射仪(XRD)分析球磨后粉末的显微组织结构及物相,研究不同球磨时间对制备TiB_2-Ni(Al)复合粉末物相演变、组织结构及粒子间界面结合状态的影响。结果在球磨过程中,球磨时间越长,Ni/Al间的塑变有利于原子之间的扩散,TiB_2陶瓷相颗粒逐渐变小。当球磨时间增长到一定程度时,延展性好的Al粉颗粒发生扁平化且其表面积不断增大,使得碎化后的Ni粉颗粒不断嵌入Al粉颗粒中,最终形成Ni(Al)固溶体。同时根据XRD分析发现,随着球磨时间的延长,TiB_2-Ni(Al)复合粉末中的Al峰逐渐减小,说明Al不断固溶到Ni中,形成了一定量的Ni(Al)固溶体。结论通过机械球磨技术在球磨一定时间后可原位合成Ni(Al)固溶体,这说明随着Ni与Al之间的相互扩散有利于形成Ni(Al)固溶体。 相似文献
11.
《International Journal of Cast Metals Research》2013,26(6):358-363
AbstractEffects of trace TiB2 on solidification microstructure of Ti–6Al–4V alloy were investigated. The result shows that the microstructure of the ingot was refined by the added TiB2. The grain size and α lath size were reduced gradually with the increase in TiB2. The grain size is reduced by about an order of magnitude with an addition of 0·96 wt-%TiB2, and the dendrite appears in the ingot. Such a tendency is similar to the change of the microstructure with boron addition. Ti–6Al–4V–B phase diagram and growth restriction factor Q are applied to analyse the influence mechanism of trace TiB2 on the microstructure. 相似文献
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利用等离子熔覆技术以Q235低碳钢为基体制备了TiB_2-TiC强化Ni基复合材料涂层,涂层中的主要物相为TiB_2、TiC和γ-Ni,硬度达1 050 HV0.5,涂层与基体呈冶金结合状态。分别采用Al2O3陶瓷球和不锈钢球为对摩副,在30、60和120 N磨损载荷下进行往复干滑动摩擦磨损试验。结果表明:Al2O3陶瓷球为对摩副时,低载荷下(30 N)表现为微切削磨损形式;60 N载荷时,出现压实层的结构,降低了摩擦因数,磨损机理转变为粘着磨损的形式;当载荷增加到120 N时,磨损机理为氧化磨损和剥层磨损。而采用不锈钢磨球时,涂层硬度大于对摩不锈钢球硬度,磨球发生剪切破坏,部分转移到涂层表面,相对于Al2O3陶瓷磨副时具有更大的粘着效应,且随着载荷的增大转移量增加,粘着磨损加剧,所以摩擦因数呈现出随着载荷加大一直上升的趋势。 相似文献
15.
对25vol% B4Cp2009/Al复合材料进行等温压缩实验,采用的温度范围为300℃—500℃,应变速率范围为0.001s-1—1s-1。结果表明,B4Cp2009/Al复合材料的高温流变曲线随着变形温度的升高和应变速率的降低而下降。对流变曲线进行了摩擦修正,修正后的流变应力值低于实验结果。摩擦力的影响随着温度的降低和应变速率的增大而更明显。随后构建了基于Arrhenius形式的本构方程,求解了不同应变量下的材料常数(α,n,Q和A)。与实验结果进行对比,利用构建的本构方程计算得到的流变应力值具有很高的计算精度,相关系数达到0.992。研究发现,较高的温度和较低的应变速率有助于B4Cp2009/Al复合材料的高温热变形。 相似文献
16.
研究了添加晶种的碳热还原SiO2法制取Si3N4/SiC复合粉末的工艺。发现反应温度的升高、反应时间的延长、原料SiO2粉比表面的增大、添加Si3N4晶种以及提高N2流速,均有利于Si3N4、SiC相含量的增加。当SiO2:C为1:2,加入10Wt%Si3N4品种时,在1350℃下于N2流速为0.4m3·h-1气氛下反应4h,可得到平均粒度为0.46m,含N23.9wt%、C6.25Wt%、O2.90wt%的Si3N4/SiC超细复合粉末。 相似文献
17.
采用粉末液相模锻技术制备出近全致密Al-5.3%Cu-3.0%h-BN(质量分数,下同)复合材料,研究了该技术制备的复合材料的致密化及界面结合状况。采用SEM、XRD、TEM等分析手段对球磨前后粉末形貌、复合材料显微结构及物相组成进行表征,利用布氏硬度计对复合材料硬度进行测试。结果表明:在大量液相存在的情况下,施加外力可有效促进复合材料的致密化。粗铝粉(35μm)制备的复合材料晶粒呈细条状,具有方向性,T6热处理后发生原位再结晶;细铝粉(2μm)制备的复合材料晶粒细小,晶粒形貌不明显。复合材料界面由Al/Al2O3/BN组成,清晰可见,结合紧密。复合材料与基体合金相比,硬度提高近15%,细铝粉制备的复合材料硬度比粗铝粉略高。 相似文献
18.
WuBian Tian Hideki KitaHideki Hyuga Naoki Kondo 《Journal of Alloys and Compounds》2011,509(5):1819-1823
TiB2-C preforms formed with different compositions and processing parameters were reactively infiltrated by Si melts at 1450 °C to fabricate TiB2-SiC-Si composites. Phase constituent and microstructure of these composites were analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The resulting composites are generally composed of TiB2 and reaction-formed β-SiC major phases, together with a quantity of residual Si. Unreacted carbon is detected in the samples with a starting composition of 2TiB2 + 1C formed at higher pressure and in all of the ones at the composition of 1TiB2 + 1C. The distribution of these phases is fairly homogeneous in microstructure. TiB2-SiC-Si composites show good mechanical properties, with representative values of 19.9 GPa in hardness, 395 GPa in elastic modulus, 3.5 MPa m1/2 in fracture toughness and 604 MPa in bending strength. The primary toughening and strengthening mechanism is attributed to the crack deflection of TiB2 particles. 相似文献
19.
碳化硼-硼化钛复合陶瓷的制备 总被引:2,自引:1,他引:2
研究了TiB2、TiC、Ti三种添加剂对超细B4C粉末的无压烧结(2 200℃×1 h)密度的影响.结果表明,加入Ti粉末对B4C的烧结没有产生明显的影响,最高密度不超过86%理论密度;而TiB2对B4C的烧结致密化有明显的促进作用,当TiB2含量达到50%时,复合陶瓷的烧结密度达到92%理论密度;TiC对B4C的烧结致密化影响比较复杂,过少或过多时均不能获得最高的烧结密度,当TiC含量为30%时,密度达到最高值(94.5%理论密度).B4C-TiC反应烧结陶瓷由B4C、TiB2、C三相组成. 相似文献
20.
Sheng Li Biao Cai Ranxi Duan Lei Tang Zihan Song Dominic White Oxana V. Magdysyuk Moataz M. Attallah 《金属学报(英文版)》2022,35(1):78
Isotropy in microstructure and mechanical properties remains a challenge for laser powder bed fusion (LPBF) processed materials due to the epitaxial growth and rapid cooling in LPBF. In this study, a high-strength TiB2/Al-Cu composite with random texture was successfully fabricated by laser powder bed fusion (LPBF) using pre-doped TiB2/Al-Cu composite powder. A series of advanced characterisation techniques, including synchrotron X-ray tomography, correlative focussed ion beam-scanning electron microscopy (FIB-SEM), scanning transmission electron microscopy (STEM), and synchrotron in situ X-ray diffraction, were applied to investigate the defects and microstructure of the as-fabricated TiB2/Al-Cu composite across multiple length scales. The study showed ultra-fine grains with an average grain size of about 0.86 μm, and a random texture was formed in the as-fabricated condition due to rapid solidification and the TiB2 particles promoting heterogeneous nucleation. The yield strength and total elongation of the as-fabricated composite were 317 MPa and 10%, respectively. The contributions of fine grains, solid solutions, dislocations, particles, and Guinier-Preston (GP) zones were calculated. Failure was found to be initiated from the largest lack-of-fusion pore, as revealed by in situ synchrotron tomography during tensile loading. In situ synchrotron diffraction was used to characterise the lattice strain evolution during tensile loading, providing important data for the development of crystal-plasticity models. 相似文献