共查询到20条相似文献,搜索用时 31 毫秒
1.
Bulk WC-Al2O3 composites prepared by spark plasma sintering 总被引:1,自引:0,他引:1
Donghai ZhengXiaoqiang Li Xuan AiChao Yang Yuanyuan Li 《International Journal of Refractory Metals and Hard Materials》2012,30(1):51-56
WC and WC-Al2O3 materials without metallic binder addition were densified by spark plasma sintering in the range of 1800-1900 °C. The densification behavior, phase constitution, microstructure and mechanical properties of pure WC and WC-Al2O3 composite were investigated. The addition of Al2O3 facilitates sintering and increases the fracture toughness of the composites to a certain extent. An interesting phenomenon is found that a proper content of Al2O3 additive helps to limit the formation of W2C phase in sintered WC materials. The pure WC specimen possesses a hardness (HV10) of 25.71 GPa, fracture toughness of 4.54 MPa·m1/2, and transverse fracture strength of 862 MPa, while those of WC-6.8 vol.% Al2O3 composites are 24.48 GPa, 6.01 MPa·m1/2, and 1245 MPa respectively. The higher fracture toughness and transverse fracture strength of WC-6.8 vol.% Al2O3 are thought to result from the reduction of W2C phase, the crack-bridging by Al2O3 particles and the local change in fracture mode from intergranular to transgranular. 相似文献
2.
Shuigen Huang Omer Van der Biest Jef Vleugels 《International Journal of Refractory Metals and Hard Materials》2009,27(6):1019-1023
WC based composites with 5, 10 and 20 vol.% Fe3Al binder were consolidated via pulsed electric current sintering (PECS) in the solid state for 4 min at 1200 °C under a pressure of 90 MPa. Microstructural analysis revealed a homogeneous Fe3Al binder distribution, ultrafine WC grains and dispersed Al2O3 particle clusters. The WC-5 vol.% Fe3Al composite combines an excellent Vickers hardness of 25.6 GPa with very high Young’s modulus of 693 GPa, a fracture toughness of 7.6 MPa m1/2 and flexural strength of 1000 MPa. With increasing Fe3Al binder content, the hardness and stiffness decreased linearly to 19.9 and 539 GPa, respectively with increasing binder content up to 20 vol.%, while the fracture toughness and flexural strength were hardly influenced by the binder content. Compared to WC–Co cemented carbides processed under exactly the same conditions, the WC–Fe3Al composites exhibit a substantially higher hardness and Young’s modulus. 相似文献
3.
R. Anandkumar A. Almeida R. Vilar J. Th. M. De Hosson 《Surface & coatings technology》2007,201(24):9497-9505
Coatings of a composite material consisting of an Al-Si matrix reinforced with SiC particles were produced by laser cladding on UNS A03560 cast Al-alloy substrates from mixtures of powders of Al-12 wt.% Si alloy and SiC. The influence of the processing parameters on the microstructure and abrasive wear resistance of the coatings was studied. For an interaction time of 0.08 s and a power density of 330 MW/m2, corresponding to a specific energy of 26 MJ/m2, the interaction between SiC and liquid Al is limited and the reinforcement particles remain essentially undissolved. The coating's microstructure is formed of SiC particles dispersed in a matrix consisting of primary α-Al dendrites and interdendritic α-Al + Si eutectic. For interaction times of 0.3 and 0.45 s and a power density of 193 MW/m2, corresponding to specific energies of 58 and 87 MJ/m2, SiC reacts with molten Al and partially dissolves. The resulting microstructure consists of undissolved SiC particles, found mainly at the bottom of the clad tracks, where the maximum temperature reached during processing is lower, and Al4SiC4 and Si particles dispersed in a matrix of α-Al + Si eutectic. The coatings prepared with higher specific energy (58 MJ/m2) present a hardness of 250 V and an abrasive wear rate in three-body abrasion tests with SiC as abrasive of 1.7 × 10− 4 mm3/m, while those produced with 26 MJ/m2 present a hardness of 120 V and a wear rate of 0.43 × 10− 4 mm3/m. These results show that Al4SiC4 and Si increase the hardness of the material by dispersion hardening but do not contribute to its abrasive wear resistance, because they are softer than the abrasive particles, and confirm that the parameters used to prepare Al-Si-SiC composite coatings by laser cladding must be selected so that only minimal reactions occur between SiC and molten Al. 相似文献
4.
Dongdong Gu Yves-Christian HagedornWilhelm Meiners Konrad WissenbachReinhart Poprawe 《Surface & coatings technology》2011,205(10):3285-3292
A novel Selective Laser Melting (SLM) process was applied to prepare bulk-form TiC/Ti5Si3 in-situ composites starting from Ti/SiC powder system. The influence of the applied laser energy density on densification, microstructure, and mechanical performance of SLM-processed composite parts was studied. It showed that the uniformly dispersed TiC reinforcing phase having a unique network distribution and a submicron-scale dendritic morphology was formed as a laser energy density of 0.4 kJ/m was properly settled. The 96.9% dense SLM-processed TiC/Ti5Si3 composites had a high microhardness of 980.3HV0.2, showing more than a 3-fold increase upon that of the unreinforced Ti part. The dry sliding wear tests revealed that the TiC/Ti5Si3 composites possessed a considerably low friction coefficient of 0.2 and a reduced wear rate of 1.42 × 10− 4 mm3/Nm. The scanning electron microscope (SEM) characterization of the worn surface morphology indicated that the high wear resistance was due to the formation of adherent and strain-hardened tribolayer. The densification rate, microhardness, and wear performance generally decreased at a higher laser energy density of 0.8 kJ/m, due to the formation of thermal cracks and the significant coarsening of TiC dendritic reinforcing phase. 相似文献
5.
Densification, microstructure and tribomechanical properties of spark plasma sintering (SPS) processed β-SiAlON (20–40 wt%) bonded WC matrix composites have been reported. All the specimens achieved almost their theoretical density values after SPS at 1750 °C for 25 min under 40 MPa. Incorporation of β-SiAlON in WC significantly altered the densification trend of the composites resembling that of pure β-SiAlON. Microstructural investigations using scanning and transmission electron microscopy revealed formation of principally equiaxed, micron sized WC grains surrounded by the sub-micron to micron sized β-SiAlON phase. The interface region between WC and β-SiAlON was found to be free of any reaction product. Energy dispersive X-ray spectrum confirmed presence of characteristics elements in both WC and β-SiAlON phases in the composite. The maximum Vickers hardness (~18 GPa) and fracture toughness (~6.8 MPa-m0.5) under 10 kgf were obtained for the 30 wt% β-SiAlON/WC composite. These were almost 6% and 50% higher, respectively, than those obtained for pure WC. Indentation size effect (ISE) analyses of some selected specimens indicated moderate sensitivity towards ISE (Meyer's exponent = 1.802) of the 30 wt% β-SiAlON/WC composite and higher true hardness (~15.4 GPa) than those obtained for both the constituent phases. The load dependence of fracture toughness of some selected specimens has also been reported. Unlubricated wear studies under 30 N up to 250 m using ball-on-disc configuration indicated ~46–55 times higher specific wear rate of the β-Si3N4 ball when rubbed against the composites compared to that (~8 × 10−6 mm3/N-m) obtained against pure WC. Formation of compacted flaky tribo-layer within the wear track of the composites was evidenced. 相似文献
6.
J. Lin J.J. Moore W.C. Moerbe M. Pinkas B. Mishra G.L. Doll W.D. Sproul 《International Journal of Refractory Metals and Hard Materials》2010
The paper will present the state-of-art in the process, structure and properties of nanostructured multifunctional tribological coatings used in different industrial applications that require high hardness, toughness, wear resistance and thermal stability. The optimization of these coating systems by means of tailoring the structure (graded, superlattice and nanocomposite systems), composition optimization, and energetic ion bombardment from substrate bias voltage control to provide improved mechanical and tribological properties will be assessed for a range of coating systems, including nanocrystalline graded Cr1−xAlxN coatings, superlattice CrN/AlN coatings and nanocomposite Cr–B–N and TiC/a-C coatings. The results showed that the superlattice CrN/AlN coating exhibited a super hardness of 45 GPa when the bilayer period Λ was about 3.0 nm. Improved toughness and wear resistance have been achieved in the CrN/AlN multilayer and graded CrAlN coatings as compared to the homogeneous CrAlN coating. For the TiC/a-C coatings, increasing the substrate bias increased the hardness of TiC/a-C coatings up to 34 GPa (at −150 V) but also led to a decrease in the coating toughness and wear resistance. The TiC/a-C coating deposited at a −50 V bias voltage exhibited an optimized high hardness of 28 GPa, a low coefficient of friction of 0.19 and a wear rate of 2.37 × 10−7 mm3 N−1 m−1. The Cr–B–N coating system consists of nanocrystalline CrB2 embedded in an amorphous BN phase when the N content is low. With an increase in the N content, a decrease in the CrB2 phase and an increase in the amorphous BN phase were identified. The resulting structure changes led to both decreases in the hardness and wear resistance of Cr–B–N coatings. 相似文献
7.
Jianliang Lin William D. Sproul John J. MooreSabrina Lee Sterling Myers 《Surface & coatings technology》2011,205(10):3226-3234
As a variation of high power pulsed magnetron sputtering technique, modulated pulse power (MPP) magnetron sputtering can achieve a high deposition rate while at the same time achieving a high degree of ionization of the sputtered material with low ion energies. These advantages of the MPP technique can be utilized to obtain dense coatings with a small incorporation of the residual stress and defect density for the thick coating growth. In this study, the MPP technique has been utilized to reactively deposit thick Cr2N and CrN coatings (up to 55 μm) on AISI 440C steel and cemented carbide substrates in a closed field unbalanced magnetron sputtering system. High deposition rates of 15 and 10 μm per hour have been measured for the Cr2N and CrN coating depositions, respectively, using a 3 kW average target power (16.7 W/cm2 average target power density), a 50 mm substrate to target distance and an Ar/N2 gas flow ratio of 3:1 and 1:1. The CrN coatings showed a denser microstructure than the Cr2N coatings, whereas the Cr2N coatings exhibited a smaller grain size and surface roughness than those of the CrN coatings for the same coating thickness. The compressive residual stresses in the CrN and Cr2N coatings increased as the coating thickness increased to 30 μm and 20 μm, respectively, but for thicker coatings, the stress gradually decreased as the coating thickness increased. The CrN coatings exhibited an increase in the scratch test critical load as the thickness was increased. Both CrN and Cr2N coatings showed a decrease in the hardness and an increase in the sliding coefficient of friction as the coating thickness increased from 2.5 to 55 μm. However, the wear rate of the CrN coatings decreased significantly as the coating thickness was increased to 10 μm or higher. The 10-55 μm CrN coating exhibited low wear rates in the range of 3.5-5 × 10−7 mm3 N−1 m−1. To the contrary, the Cr2N coating exhibited relatively low wear resistance in that high wear rates in the range of 3.5 to 7.5 × 10−6 mm3 N−1 m−1 were observed for different thicknesses. 相似文献
8.
Microstructure, mechanical and wear properties of laser processed SiC particle reinforced coatings on titanium 总被引:1,自引:0,他引:1
Mitun DasSandip Bysakh Debabrata Basu T.S. Sampath KumarVamsi Krishna Balla Susmita BoseAmit Bandyopadhyay 《Surface & coatings technology》2011,205(19):4366-4373
Laser processing of Ti-SiC composite coating on titanium was carried out to improve wear resistance using Laser Engineered Net Shaping (LENS™) — a commercial rapid prototyping technology. During the coating process a Nd:YAG laser was used to create small liquid metal pool on the surface of Ti substrate in to which SiC powder was injected to create Ti-SiC metal matrix composite layer. The composite layers were characterized using X-ray diffraction, scanning and transmission electron microscopy equipped with fine probe chemical analysis. Laser parameters were found to have strong influence on the dissolution of SiC, leading to the formation of TiSi2, Ti5Si3 and TiC with a large amount of SiC on the surface. Detailed matrix microstructural analysis showed the formation of non-stoichiometric compounds and TiSi2 in the matrix due to non-equilibrium rapid solidification during laser processing. The average Young's modulus of the composite coatings was found to be in the range of 602 and 757 GPa. Under dry sliding conditions, a considerable increase in wear resistance was observed, i.e., 5.91 × 10− 4 mm3/Nm for the SiC reinforced coatings and 1.3 × 10−3 mm3/Nm for the Ti substrate at identical test conditions. 相似文献
9.
a-CNx/TiN multilayer films were deposited onto high-speed steel substrates by pulsed laser ablation of graphite and Ti target alternately in nitrogen gas. The composition, morphology and microstructure of the films were characterized by energy dispersive X-ray spectroscopy (EDS), scanning electron microscopy (SEM), X-ray diffraction (XRD) and Raman spectroscopy. The tribological properties of the films in humid air were investigated using a ball-on-disk tribometer. The multilayer films consist of crystalline TiN, metallic Ti and amorphous CNx (a-CNx). With an increase in thickness ratio of CNx to bilayer, the hardness of multilayer film decreases, friction coefficient decreases from 0.26 to 0.135, and wear rate increases. The film with thickness ratio of CNx to bilayer of 0.47 exhibits a maximum hardness of 30 GPa and excellent wear rate of 2.5 × 10− 7 mm3 N− 1 m− 1. The formation of tribo-layer was observed at contact area of Si3N4 ball. The film undergoes the combined wear mechanism of abrasion wear and adhesion wear. 相似文献
10.
Alumina-based nanocomposites reinforced with niobium and/or carbon nanotubes (CNT) were fabricated by advanced powder processing techniques and consolidated by spark plasma sintering. Raman spectroscopy revealed that single-walled carbon nanotubes (SWCNT) begin to break down at sintering temperatures >1150 °C. Nuclear magnetic resonance showed that, although thermodynamically unlikely, no Al4C3 formed in the CNT-alumina nanocomposites, such that the nanocomposite can be considered as purely a physical mixture with no chemical bond formed between the nanotubes and ceramic matrix. In addition, in situ single-edge notched bend tests were conducted on niobium and/or CNT-reinforced alumina nanocomposites to assess their toughness. Despite the absence of subcritical crack growth, average fracture toughness values of 6.1 and 3.3 MPa m1/2 were measured for 10 vol.% Nb and 10 vol.% Nb-5 vol.% SWCNT-alumina, respectively. Corresponding tests for the alumina nanocomposites containing 5 vol.% SWCNT, 10 vol.% SWCNT, 5 vol.% double-walled-CNT and 10 vol.% Nb yielded average fracture toughnesses of 3.0, 2.8, 3.3 and 4.0 MPa m1/2, respectively. It appears that the reason for not observing improvement in fracture toughness of CNT-reinforced samples is because of either damage to CNTs or possibly non-optimal interfacial bonding between CNT-alumina. 相似文献
11.
Xin Sun Wenbo HanPing Hu Zhi WangXinghong Zhang 《International Journal of Refractory Metals and Hard Materials》2010
The high relative density of the ZrB2-based composite toughened by 25 vol.%Nb (ZN) was hot-pressed at reduced temperatures with low pressure of 30 MPa. Compared with the toughness of 2.3–3.5 MPa m1/2 and strength of 350 MPa of the monolithic ZrB2, the toughness and strength of the ZN composite were improved to 6.7 MPa m1/2 and 773 MPa, respectively, due to the addition of ductile Nb. The toughening mechanisms are crack deflection and branching as well as stress relaxation near the crack tip. Furthermore, the densification mechanism was analyzed and discussed. The results here pointed to a potential method for improving fracture toughness and strength of ZrB2-based ceramics. 相似文献
12.
D.H. Xiao Y.H. HeM. Song N. LinR.F. Zhang 《International Journal of Refractory Metals and Hard Materials》2010
The nanocomposite WC–10Co powders were prepared through planetary ball milling method. The effects of minor Y2O3 and NbC additions on structure, hardness and fracture toughness of ultrafine WC–10Co alloys were investigated using X-ray diffraction, optical microscope, scanning electron microscope and mechanical properties tests. The results show that minor NbC additions refine the WC grains and increase the hardness of the base alloys. The additions of Y2O3 decrease the volume fraction of Co3W3C phase in ultrafine WC–10Co alloys after low pressure sintering, and thus increase the fracture toughness of the base alloys from 6.2 MN m−3/2 to 9.8 MN m−3/2. 相似文献
13.
Nanocrystallized Cr1−xAlxN films with various Al contents (0 to 68 at.%) were deposited by pulsed closed field unbalanced magnetron sputtering (P-CFUBMS). The effects of aluminum content on the microstructure, mechanical and tribological properties of the Cr1−xAlxN films have been investigated. It was found that the hardness and elastic modulus of Cr1−xAlxN films increased with increasing Al contents in the films and reached the highest value of 36 GPa and 370 GPa, respectively, at an Al content of 58.5 at.%. Addition of Al beyond 64.0 at.% resulted in a change in crystal structure from B1 cubic to B4 hexagonal phase. The wear resistance improved gradually with the increase of Al in the Cr1−xAlxN films. A combination of the abrasive and adhesive wear mechanism was proposed based on the SEM and EDS analysis of the wear track. The steady state dry coefficient of friction measured against a WC ball for the Cr1−xAlxN films were in the range of 0.36-0.55, and the wear rate was in the 10− 6 mm3 N− 1 m− 1 range. 相似文献
14.
X.Q. OuM. Song T.T. ShenD.H. Xiao Y.H. He 《International Journal of Refractory Metals and Hard Materials》2011,29(2):260-267
The ultrafine grained WC-10Co-0.45Cr3C2-0.25VC alloys were fabricated through planetary ball milling and low pressure sintering. The effects of the cobalt particle size, milling speed and sintering temperature on the microstructure, hardness and fracture toughness of the ultrafine grained alloys were investigated using optical microscopy, scanning electron microscopy and mechanical testing. The results showed that the mechanical properties of the low pressure-sintered alloys substantially depend on the milling speed and sintering temperature. At the same time, the hardness and fracture toughness of the samples can be increased from 1703 MPa and 8.90 MN m−3/2 to 1789 MPa and 11.21 MN m−3/2, respectively, when the cobalt particle size is reduced from 17 μm to 1.4 μm. 相似文献
15.
Graphene nanosheets/poly(3-hexylthiophene) (GNs/P3HT) composites were prepared by oxidative polymerization of 3-hexylthiophene in a GNs dispersed chloroform solution. The phase composition of the composite materials was analyzed by X-ray diffraction and Fourier transform infrared spectra. The thermoelectric properties of the cold pressed composite pellets with different GNs loadings were measured at room temperature. As the GNs loading increased from 0 to 30 wt.%, the electrical conductivity of the composites dramatically increased from ∼10−6 to ∼1.2 S/cm while the Seebeck coefficient slightly increased from 33.15 to 35.46 μV/K. The highest power factor (∼0.16 μW m−1 K−2) was obtained in the 30 wt.% GNs/P3HT composite material. 相似文献
16.
In the present study, laser surface alloying of aluminium with WC + Co + NiCr (in the ratio of 70:15:15) has been conducted using a 5 kW continuous wave (CW) Nd:YAG laser (at a beam diameter of 0.003 m), with the output power ranging from 3 to 3.5 kW and scan speed from 0.012 m/s to 0.04 m/s by simultaneous feeding of precursor powder (at a flow rate of 1 × 10− 5 kg/s) and using He shroud at a gas flow rate of 3 × 10− 6 m3/s. The effect of laser power and scan speed on the characteristics (microstructures, phases and composition) and properties (wear and corrosion resistance) of the surface alloyed layer have been investigated in details. Laser surface alloying leads to development of fine grained aluminium with the dispersion of WC, W2C, Al4C3, Al9Co2, Al3Ni, Cr23C6, and Co6W6C. The microhardness of the alloyed zone is significantly improved to a maximum value of 650 VHN as compared to 22 VHN of the as-received aluminium substrate. The mechanism of microhardness enhancement has been established. The fretting wear behavior of the alloyed zone was evaluated against WC by Ball-on-disc wear testing unit and the mechanism of wear was established. 相似文献
17.
Effects of sintering additives on microstructure and mechanical properties of TiB2-WC ceramic-metal composite tool materials 总被引:1,自引:0,他引:1
Jinpeng SongChuanzhen Huang Bin ZouHanlian Liu Lin LiuJun Wang 《International Journal of Refractory Metals and Hard Materials》2012,30(1):91-95
TiB2-WC ceramic-metal composite tool materials were fabricated using Co, Ni and (Ni, Mo) as sintering additives by vacuum hot-pressing technique. The microstructure and mechanical properties of the composite were investigated. The composite was analyzed by the observations of scanning electron microscope (SEM), X-ray diffraction (XRD) and energy dispersive spectrometry (EDS). The microstructure of TiB2-WC ceramic-metal composites consisted of the fine WC grains and uniform TiB2 grains. The brittle phase of Ni3B4 and a few pores were found in TiB2-WC-Ni ceramic-metal composite. A lot of pores and brittle phases such as W2CoB2 and Co2B were formed in TiB2-WC-Co ceramic-metal composite. The liquid phase of Co was consumed by the reaction which led to the formation of the pores and the coarse grains of TiB2. The pores, brittle phases and coarse grains of TiB2 were harmful to the improvement of the mechanical properties of the composite. The sintering additive of (Ni, Mo) had a significant effect on the density and the mechanical properties of TiB2-WC ceramic-metal composite. The formation of intermetallic compound of MoNi4 inhibited the consumption of liquid phase of (Ni, Mo). The liquid phase of (Ni, Mo) not only inhibited the formation of the pores and the coarse grains of TiB2 but also strengthened the interface energy between WC and TiB2 grains. The grain size was fine and the average relative density of TiB2-WC-(Ni, Mo) ceramic-metal composite reached 99.1%. The flexural strength, fracture toughness and Vickers hardness of TiB2-WC-(Ni, Mo) ceramic-metal composite were 1307.0 ± 121.4 MPa, 8.19 ± 0.29 MPa m1/2 and 22.71 ± 0.82 GPa, respectively. 相似文献
18.
The objective of this work is to produce Al2O3-ZrO2 composite from nano-sized powders processed by coprecipitation method. Al2O3 and mixture of Al2O3 + 10 wt.% ZrO2 precipitated successfully by chemical route from aluminum sulfate and zirconium sulfate were pressed under uniaxial compression of 170 MPa and sintered at 1600 °C for 1 h. SEM investigations revealed that, pure alumina sample has a microstructure with coarse grains which anisotropically grown up to 30-40 μm in size. In alumina-zirconia composite, the structure consists of very fine equiaxed grains of typically 2 μm in which zirconia precipitates were uniformly dispersed. By adding zirconia to alumina, hardness and indentation fracture toughness were increased from 11.6 GPa to 16.8 GPa and from 3.2 MPa m1/2 to 4.9 MPa m1/2, respectively. Improvement in fracture toughness was attributed to bridging effects of zirconia particles as well as transformation toughening. 相似文献
19.
J.K. SonberR.K. Fotedar A.K. Suri 《International Journal of Refractory Metals and Hard Materials》2011,29(1):21-30
This paper presents the results of experimental investigations carried out on the synthesis of pure ZrB2 by boron carbide reduction of ZrO2 and densification with the addition of HfB2 and TiSi2. Process parameters and charge composition were optimized to obtain pure ZrB2 powder. Monolithic ZrB2 was hot pressed to full density and characterized. Effects of HfB2 and TiSi2 addition on densification and properties of ZrB2 composites were studied. Four compositions namely monolithic ZrB2, ZrB2 + 10% TiSi2, ZrB2 + 10% TiSi2 + 10% HfB2 and ZrB2 + 10% TiSi2 + 20% HfB2 were prepared by hot pressing. Near theoretical density (99.8%) was obtained in the case of monolithic ZrB2 by hot pressing at 1850 °C and 35 MPa. Addition of 10 wt.% TiSi2 resulted in an equally high density of 98.9% at a lower temperature (1650 °C) and pressure (20 MPa). Similar densities were obtained for ZrB2 + HfB2 mixtures also with TiSi2 under similar conditions. The hardness of monolithic ZrB2 was measured as 23.95 GPa which decreased to 19.45 GPa on addition of 10% TiSi2. With the addition of 10% HfB2 to this composition, the hardness increased to 23.08 GPa, close to that of monolithic ZrB2. Increase of HfB2 content to 20% did not change the hardness value. Fracture toughness of monolithic sample was measured as 3.31 MPa m1/2, which increased to 6.36 MPa m1/2 on addition of 10% TiSi2. With 10% HfB2 addition the value of KIC was measured as 6.44 MPa m1/2, which further improved to 6.59 MPa m1/2 with higher addition of HfB2 (20%). Fracture surface of the dense bodies was examined by scanning electron microscope. Intergranular fracture was found to be a predominant mode in all the samples. Crack propagation in composites has shown considerable deflection indicating high fracture toughness. An oxidation study of ZrB2 composites was carried out at 900 °C in air for 64 h. Specific weight gain vs time plot was obtained and the oxidized surface was examined by XRD and SEM. ZrB2 composites have shown a much better resistance to oxidation as compared to monolithic ZrB2. A protective glassy layer was seen on the oxidized surfaces of the composites. 相似文献
20.
Xiangbo ShenZhaohui Zhang Sai WeiFuchi Wang Shukui Lee 《Journal of Alloys and Compounds》2011,509(29):7692-7696
In situ synthesized TiB reinforced titanium matrix composites have been synthesized by spark plasma sintering (SPS) process at 950-1250 °C, using mixtures of 15 wt% TiB2 and 85 wt% Ti powders. The effects of the sintering temperature on densification behavior and mechanical properties of the TiB-Ti composites were investigated. The results indicated that with rising sintering temperatures, relative densities of the composites increase obviously, while the in situ TiB whiskers grow rapidly. As a result, bending strength of the TiB-Ti composites increases slowly at the combined actions of the factors referred above. Fracture toughness of the composites is improved remarkably due to the large volume fraction of Ti matrix, the crack deflection, pull-out and the micro-fracture of the needle-shaped TiB grains. The results also suggested that TiB-Ti composite sintered at 1250 °C by SPS process exhibits the highest relative density of 99.6% along with bending strength of 1161 MPa and fracture toughness of 13.5 MPa m1/2. 相似文献