共查询到20条相似文献,搜索用时 62 毫秒
1.
H. C. Yi J. Y. Guigné T. C. Woodger J. J. Moore 《Metallurgical and Materials Transactions B》1998,29(4):867-875
Combustion synthesis (SHS) of Ni3Ti-TiB2 metal matrix composites (MMCs) was selected to investigate the effect of gravity in a reaction system that produced a light,
solid ceramic particle (TiB2) synthesized in situ in a large volume (>50 pct) of the liquid metallic matrix (Ni3Ti). The effects of composition, green density of pellets, and nickel particle size on the combustion characteristics are
presented. Combustion reaction temperature, wave velocity, and combustion behavior changed drastically with change in reaction
parameters. Two types of density effects were observed when different nickel particle sizes were used. The structures of the
combustion zones were characterized using temperature profile analysis. The combustion zone can be divided into preflame,
reaction, and after-burning zones. The combustion mechanism was studied by quenching the combustion front. It was found that
the combustion reactions proceeded in the following sequence: formation of liquid Ni-Ti eutectic at 940 °C → Ni3Ti+NiTi phases → reduction of NiTi with B→TiB2+Ni3Ti. 相似文献
2.
H. C. Yi J. Y. Guigné T. C. Woodger J. J. Moore 《Metallurgical and Materials Transactions B》1998,29(4):877-887
Combustion synthesis (SHS) of HfB2-Al composite materials with a wide range of HfB2-to-Al ratios corresponding to either metal (Al) or ceramic (HfB2) matrix was carried out with the emphasis on 60 and 70 vol pct Al. The effects of composition and green density of pellets
on the combustion characteristics were studied. Combustion temperature, wave velocity, and reaction mode all changed drastically
with composition and green density. The combustion mechanisms were also studied using temperature profile analysis. The combustion
zone can be divided into preflame and main reaction zones, and the width of the latter was much larger than that of the former.
It was also found that the combustion reaction was initiated at the melting of the aluminum and consisted of a two-step reaction
sequence corresponding to the initial formation of Al3Hf and, subsequently, HfB2 compounds. The formation of Al3Hf triggered the HfB2 formation according to the following reaction mechanism:
相似文献
3.
4.
Douglas E. Burkes John J. Moore Guglielmo Gottoli Hu Chun Yi 《Metallurgical and Materials Transactions A》2006,37(3):1045-1053
Combustion synthesis (CS) of nickel, titanium, and carbon (graphite) reactant particles can result in NiTi-TiC (stoichiometric)
or Ni3Ti-TiC
x
(nonstoichiometric) composites. Since NiTi exhibits both superelasticity and shape memory properties while Ni3Ti does not, it is important to understand the SHS reaction conditions under which each of these composite systems may be
synthesized. The stoichiometry of TiC
x
, for which 0.3 ≤ x ≤ 0.5, has an important controlling effect on the formation of either Ni3Ti or NiTi; i.e., formation of TiC0.7 results in a depletion of titanium and formation of Ni3Ti. This deficiency should be considered when developing the SHS reaction. This article examines the SHS conditions under
which Ni3Ti-TiC
x
composites are produced. Ignition, combustion, and microstructure characteristics of nickel, titanium, and carbon (graphite)
particles were investigated as a function of initial relative density and thermophysical properties of the reactant mixture.
Combination of the thermophysical properties and burning velocities controlled TiC
x
particle size, yielding a dependence of particle size on cooling rate. Theoretical calculations were performed and are in
good agreement with the experimental data presented. 相似文献
5.
Y. Choi M. E. Mullins K. Wijayatilleke J. K. Lee 《Metallurgical and Materials Transactions A》1992,23(9):2387-2392
Fine fibrous titanium carbide (TiC) was processed through the self-propagating high-temperature synthesis (SHS) method and
employed to fabricate aluminum matrix composites. Two consol-idation methods were investigated: (1) combustion synthesis of
TiC fiber/Al composites directly using titanium powders and carbon fibers ignited simultaneously with varying amounts of the
matrix metal powder and (2) combustion synthesis of TiC using titanium powders and carbon fibers followed by consolidation
into different amounts of the metal matrix powder, Al,via hot isostatic pressing (HIP). In the former method, when the amount of the Al in the matrix was increased, the maximum temperature
obtained by the combustion reaction decreased and the propagation of the synthesis reactions became difficult to maintain.
Preheating was required for the mixture of reactants with more than approximately 5 mole pct aluminum matrix powders in order
to ignite and maintain the propagation rate. Microstructural analysis of the products from the Al/C/Ti reaction without preheating
shows that small amounts of an aluminum carbide phase (AI4C3) are present. In the second method, following separation of the
individual fibers in the TiC product, dense composites containing the SHS products were obtained by HIP of a mixture of the
TiC fibers and Al powders. No ternary phase was formed during this procedure.
Formerly Graduate Research Assistant, Department of Chemical Engineering, Michigan Technological University, is with Particle
Technology, Inc., Hanover, MD 21076.
This paper is based on a presentation made in the symposium “Reaction Synthesis of Materials” presented during the TMS Annual
Meeting, New Orleans, LA, February 17–21, 1991, under the auspices of the TMS Powder Metallurgy Committee. 相似文献
6.
I. P. Borovinskaya T. G. Akopdzhanyan T. I. Ignatieva E. A. Chemagina 《Russian Journal of Non-Ferrous Metals》2017,58(4):405-410
Synthesis of aluminum oxynitride (γ-AlON) in conditions of self-propagating high-temperature synthesis (SHS) gas-statting under high pressures (10–100 MPa) of gaseous nitrogen, including the mode of so-called coupled combustion reactions (chemical furnaces) is investigated. It is shown that chemical and phase compositions of combustion products, as well as their structure and morphology of powder particles, depend on the reagent ratio in Al–Al2O3 initial mixture, as well as on nitrogen pressure, combustion temperature of highly exothermic components of chemical furnaces, and grade of initial reagents. The structure of γ-AlON powder particles are determind and its relation with operation conditions of SHS. Optimal SHS parameters for Al5O6N (γ-AlON) formation are established. 相似文献
7.
Douglas E. Burkes Guglielmo Gottoli John J. Moore Hu Chun Yi 《Metallurgical and Materials Transactions A》2006,37(12):1045-1053
Combustion synthesis (CS) of nickel, titanium, and carbon (graphite) reactant particles can result in NiTi−TiC (stoichiometric)
or Ni3Ti−TiC
x
(nonstoichiometric) composites. Since NiTi exhibits both superelasticity and shape memory properties while Ni3Ti does not, it is important to understand the SHS reaction conditions under which each of these composite systems may be
synthesized. The stoichiometry of TiC
x
, for which 0.3≤x≤0.5, has an important controlling effect on the formation of either Ni3Ti or NiTi; i.e., formation of TiC0.7 results in a depletion of titanium and formation of Ni3Ti. This deficiency should be considered when developing the SHS reaction. This article examines the SHS conditions under
which Ni3Ti−TiC
x
composites are produced. Ignition, combustion and microstructure characteristics of nickel, titanium, and carbon (graphite)
particles were investigated as a function of initial relative density and thermophysical properties of the reactant mixture.
Combination of the thermophysical properties and burning velocities controlled TiC
x
particle size, yielding a dependence of particle size on cooling rate. Theoretical calculations were performed and are in
good agreement with the experimental data presented.
Guglielmo Gottoli, formerly Graduate Research Assistant, Metallurgical and Materials Engineering Department, Institute for
Space Resources, Colorado School of Mines 相似文献
8.
Douglas E. Burkes Guglielmo Gottoli John J. Moore Hu Chun Yi 《Metallurgical and Materials Transactions A》2006,37(13):1045-1053
Combustion synthesis (CS) of nickel, titanium, and carbon (graphite) reactant particles can result in NiTi−TiC (stoichiometric)
or Ni3Ti−TiC
x
(nonstoichiometric) composites. Since NiTi exhibits both superelasticity and shape memory properties while Ni3Ti does not, it is important to understand the SHS reaction conditions under which each of these composite systems may be
synthesized. The stoichiometry of TiC
x
, for which 0.3≤x≤0.5, has an important controlling effect on the formation of either Ni3Ti or NiTi;i.e., formation of TiC0.7 results in a depletion of titanium and formation of Ni3Ti. This deficiency should be considered when developing the SHS reaction. This article examines the SHS conditions under
which Ni3Ti−TiC
x
composites are produced. Ignition, combustion and microstructure characteristics of nickel, titanium, and carbon (graphite)
particles were investigated as a function of initial relative density and thermophysical properties of the reactant mixture.
Combination of the thermophysical properties and burning velocities controlled TiC
x
particle size, yielding a dependence of particle size on cooling rate. Theoretical calculations were performed and are in
good agreement with the experimental data presented.
Guglielmo Gottoli, formerly Graduate Research Assistant, Metallurgical and Materials Engineering Department, Institute for
Space Resources, Colorado School of Mines 相似文献
9.
The self-propagating mode of combustion synthesis (SHS) of Ni3Al starting from compacts of stoichiometrically mixed Ni and Al powders readily forms fully reacted structures with about
3 to 5 pct porosity, if green density of the compacts is greater than about 75 pct of theoretical. SHS-produced Ni3Al matrix composites with up to 2 wt pct A12O3 whiskers also have relatively low porosity levels. Porosity increases rapidly with lower green densities, higher Al2O3, or SiC whisker contents, and the degree of reaction completeness diminishes. The SiC whiskers undergo reaction with the
matrix, while Al2O3 whiskers are nonreactive. All of these observations correlate well with temperature measurements made during the course of
the reaction. The SHS mode can be achieved with agglomerated particle size ratioD
Al/D
Ni ≥ 1, larger than the limit established from studies of the thermal explosion mode of combustion synthesisD
Al/D
Ni ≃ 0.3.
This paper is based on a presentation made in the symposium “Reaction Synthesis of Materials” presented during the TMS Annual
Meeting, New Orleans, LA, February 17–21, 1991, under the auspices of the TMS Powder Metallurgy Committee. 相似文献
10.
From the viewpoint of thermodynamics, using the Wilson equation and an extended Miedema model, the effect of the alloying
element on the stability of the precipitated phases during the fabrication of in-situ reinforced TiB2/Al composites was evaluated. The result shows that additions of alloying elements, such as Mg, Cu, Zr, Ni, Fe, V, and La,
can promote the formation of Al3Ti and TiB2 phases. Particularly, Zr has the most pronounced effect among these alloying elements. In addition, alloying elements can
hinder the formation of AlB2 to a small extent. The calculation results also show that it is easier for magnesium to react with the salts to form TiB2 than aluminum during the fabrication of in-situ reinforced TiB2/Al using the flux-assisted synthesis (FAS) technology. 相似文献
11.
R. K. Gupta Bhanu Pant Vijaya Agarwala P. Ramkumar P. P. Sinha 《Transactions of the Indian Institute of Metals》2010,63(4):715-718
TiB2 reinforced in-situ titanium aluminide matrix composite was made through reaction synthesis process using high purity elemental
powders of Ti, Al, Cr, Nb and B. XRD of the synthesized block showed presence of mainly Al3Ti and TiB2 phases. To obtain γ Ti aluminide based matrix, the material was homogenized in two phase region (α2+γ). Presence of γ phase matrix alongwith α2 was confirmed through XRD, SEM and TEM. Uniform distribution of TiB2 phase was confirmed through elemental mapping and by analyzing specimens of different locations. Differential scanning calorimetry
of powder mixture showed presence of endothermic peak for Al melting and exothermic peak of Ti aluminide and TiB2 formation. 相似文献
12.
This article focuses on the characterization of self-propagating high-temperature synthesis (SHS) reactions that occur in
powder compacts containing titanium, boron, and aluminum. Interest in this powder system is based on the critical need to
develop new joining techniques for bonding ceramics to metals. The exothermic reactions of particular interest in this study
include those that generate TiB2, TiB, Ti3Al, and TiAl from their elemental powders. Data from differential thermal analysis (DTA), thermogravimetric analysis (TGA),
and X-ray diffractometry are presented. These results demonstrate that the gas phase surrounding the SHS powders plays an
important role in initiating the SHS reaction and in determining which reaction products will form in the final bond. 相似文献
13.
Effects of TiB2/TiCx ratios on compression properties and abrasive wear resistance of 50?vol.-% (TiB2–TiCx)/Al–Cu composites fabricated via the combustion synthesis (CS) method assisted with hot press from the Al–Ti–B4C system were studied. With decrease in the TiB2/TiCx ratio from 3:1 to 1:3, the shape of TiB2 changed from platelike to clubbed while the size of TiCx particles increased, which directly led to different mechanical properties. The 50?vol.-% (TiB2–TiCx)/Al–Cu composite with the TiB2/TiCx ratio of 2:1 exhibited good compression strength without sacrificing the fracture strain, while the composite possessed the highest abrasive wear resistance when the TiB2/TiCx ratio was 3:1. The appropriate TiB2/TiCx ratio was recommended to be 2:1 in this research. 相似文献
14.
J. Vleugels K. C. Hari Kumar R. G. Vitchev O. van der Biest B. Basu 《Metallurgical and Materials Transactions A》2002,33(12):3847-3859
Fretting tests under dry unlubricated conditions (22 °C to 25 °C, 50 to 55 pct RH) were performed on monolithic TiB2, TiB2-based cermet with a Ni3(Al,Ti) binder, sialon-TiB2, and ZrO2-TiB2 composites to assess their relative wear performance against bearing-grade steel. Based on the measured friction and wear
data, the relative ranking of the investigated fretting couples is established. The fretting wear of all investigated tribocouples
was found to fall in the tribochemical wear regime. The extent of the tribochemical reaction was observed to be strongly dependent
on the chemical solubility of TiB2 and the binder phases in steel at the tribocontacts and was accompanied by tribo-oxidation. For the monolithic TiB2 and TiB2-based cermet materials, however, abrasion and adhesive wear, in addition to the tribochemical reactions, are found to be
the cause for the high volumetric wear loss of these tribosystems. On the other hand, mild abrasion coupled with reduced tribochemical
reactions is observed to play a major role in the low wear loss of the ZrO2-TiB2/steel fretting couple. Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) analysis of the tribochemical layer
formed in the monolithic TiB2/steel tribocouple revealed the formation of mixed oxides containing predominantly TiO2 (anatase), B2O3, and Fe2O3. Based on the thermodynamic calculations and the experimental observations, a tribochemical wear model is proposed to explain
the observed tribological behavior of the investigated tribosystems. 相似文献
15.
Boron removal by titanium addition in solidification refining of silicon with Si-Al melt 总被引:4,自引:0,他引:4
Takeshi Yoshikawa Kentaro Arimura Kazuki Morita 《Metallurgical and Materials Transactions B》2005,36(6):837-842
In order to effectively remove B from Si for its use in solar cells, a process involving B removal by solidification refining
of Si using a Si-Al melt with Ti addition was investigated. For clarifying the effect of Ti addition on B removal from the
Si-Al melt, TiB2 solubilities in Si-64.6 at. pct Al melt at 1173 K and Si-60.0 at. pct Al melt at 1273 K were determined by measuring the
equilibrium concentrations of B and Ti in the presence of TiB2 precipitates. The small solubilities of TiB2 in the Si-Al melt indicate the effective removal of B from the Si-Al melt by Ti addition. Further, solidification experiments
of Si-Al alloys containing B by Ti addition were performed, and the effect of Ti addition on the solidification refining of
Si with the Si-Al melt was successfully confirmed. 相似文献
16.
Grain refinement in aluminum alloyed with titanium and boron 总被引:3,自引:0,他引:3
The aluminum corner of the ternary Al-B-Ti diagram was explored. A eutectic: Liq — Al + TiAl3 + (Al, Ti)B2 was found at approximately 0.05 wt pct Ti, 0.01 wt pct B; 659.5‡C. TiB2 and A1B2 form a continuous series of solid solutions, but no distinct ternary phase was found. The addition of boron to aluminum-titanium
alloys expands the field of primary crystallization of TiAl3 toward lower titanium contents and steepens the liquidus. In equilibrium conditions, pronounced grain refinement is found
only in alloys in which TiAl3 is primary and nucleates the aluminum solid solution before any other impurity can act. The peritectic reaction facilitates
this priority but it is not necessary for grain refinement. Because of the low diffusivity of titanium and boron in aluminum,
equilibrium is seldom attained and in commercial practice grain refinement by TiAl3 is found also outside its equilibrium field of primary crystallization. 相似文献
17.
18.
A. F. Fedotov A. P. Amosov E. I. Latukhin V. A. Novikov 《Russian Journal of Non-Ferrous Metals》2016,57(1):33-40
A one-stage manufacturing technology of aluminum–ceramic skeleton composites by combining the processes of self-propagating high-temperature synthesis (SHS) of a porous skeleton formed by the MAX phase of the Ti2AlC composition and its impregnation by the aluminum melt under pressure (SHS compaction) is considered. A composition of the exothermic charge 2Ti + C + 22.5 wt % Al + 10 wt % TiH2, which provides the formation of a porous skeleton of the Ti2AlC phase without impurity phases by the SHS technology, is selected. It is shown that, when impregnating the hot SHS skeleton with aluminum, new phases are formed such as the MAX phase (Ti3AlC2), titanium carbide (TiC), and titanium aluminide (Al3Ti). However, the content of the basic MAX phase remains high, and the ceramic component of the material consists of Ti2AlC by 76%. When analyzing the microstructure, it is revealed that the composite has certain residual porosity after impregnation and cooling. The influence of the impregnation pressure (q = 22, 28, and 35 MPa) on the distribution of the aluminum content over the height and radius of the diametral sample section is investigated experimentally. It is shown that the nonuniform Al distribution over the sample bulk is caused by the nonuniform pressure and temperature fields, as well as the different compactibility of hot inner and colder outer sample parts. The degree of compaction of characteristic zones is leveled as the impregnation pressure increases, and the composition inhomogeneity over the sample bulk decreases. The difference in aluminum concentration over the sample bulk at q = 35 MPa does not exceed 5%. The SHS-compacted aluminum–ceramic skeleton composite based on the Ti2AlC MAX phase corresponds to high-strength Al-Zn–Mg–Cu aluminum alloys by the hardness level (HB ≈ 150 kg/mm2). 相似文献
19.
20.
《粉末冶金学》2013,56(1):65-72
AbstractThe sinterability of TiB2-Ni3(Al,Ti) based cermets has been significantly improved by aggressive milling of the starting TiB2-Ni-TiAl3 powder mixtures. This technique improves not only liquid spreading by reducing TiAl3 particle size but also eliminates alumina agglomerates and the associated porosity found after vacuum sintering. Liquid phase sintering of TiB2-Ni-TiAl3 powder mixtures involves the presence of Ni based secondary borides at low temperatures (1200°C), which react afterwards with TiAl3 particles leading to the formation of the final TiB2-Ni3(Al,Ti) eutectic liquid. Apart from improving liquid spreading around TiB2 grains, aggressive milling is also found to disperse alumina agglomerates, which reduces the porosity associated to these particles. By this refined procedure, the amount of binder phase required for full densification of TiB2 cermets by sinter hipping has been reduced from a previous limit of 16 vol.-% to 10 vol.-%. The hardness of these TiB2-10 vol.-%Ni3(Al,Ti) cermets is in the range of ultrafine WC-Co hardmetals in spite of their much coarser microstructure. 相似文献