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1.
A. Muthuchamy G. D. Janaki Ram V. Subramanya Sarma 《Transactions of the Indian Institute of Metals》2018,71(4):941-949
In the current research work, spark plasma consolidated beta-titanium alloy Ti–15V–3Cr–3Al–3Sn composites reinforced with SiC fibers (Sigma SM1240) were subjected to high temperatures (1173, 1223 and 1273 K) for different time periods (2.7, 11, 25 and 44 h) to investigate the kinetics of the chemical reactions at the fiber/matrix interface. Through microstructural studies and room temperature tensile tests, we have attempted to study the effect of the formed brittle reaction zone on the final mechanical properties of the composite. We have observed that, prior to the SiC fiber, the protective carbon coating reacts with the matrix and results in the formation of a reaction zone (predominantly TiC) at the fiber/matrix interface. The reaction zone propagates into the matrix with increase in time at the expense of the carbon coating, and finally ends with the onset of titanium silicide reaction. The reaction kinetics at the fiber/matrix interface was predominantly controlled by diffusion of carbon through the reaction zone and the activation energy for the same was calculated to be 149 kJ/mol. It was clear from the tensile test results that the mechanical properties of the composites do not earnestly decrease until the commencement of titanium silicide reaction. 相似文献
2.
T. Caulfield R. S. Bellows J. K. Tien 《Metallurgical and Materials Transactions A》1985,16(11):1961-1968
Tungsten fibers in the INCOLOY* 903 alloy were annealed for over 100 hours at 1038 °C and 1200 °C. It was found that interdiffusion
results in the formation of a reaction zone. SEM-EDS probe analysis showed that the chemistries across this zone were constant,
suggesting the zone was a compound phase. The composition of the compound was estimated to be that of a μ-type phase. The
local chemistry (in atomic percent) at the reaction zone/alloy matrix interface was found to be approximately 8 pct W, 1.2
pct Nb, 40 pct Fe, 14 pct Co, and 36 pct Ni. In addition, recrystallization was observed in both the remaining tungsten fiber
and the nearby INCOLOY 903 matrix after annealing at 1200 °C, but not at 1038 °C. The results of this study suggest that reaction
zone growth kinetics can be minimized by the reduction of Co and Fe and the increase of W in the matrix alloy. 相似文献
3.
Yoshikazu Nakamura 《Metallurgical and Materials Transactions B》1974,5(4):909-913
The oxidation behavior of an Iron-15 wt pct Chromium alloy, some containing small additions of yttrium or rare earth elements,
have been observed using a TG and an EPMA method at temperatures between 900° and 1200°C. Yttrium or rare earth element additions
to the Iron-Chromium alloy result in a rapid initial oxidation rate, but decrease the total weight gain of the Iron-Chromium
alloy at the final time of exposure. The line trace obtained indicates that the increased segregation of chromium content
in the inner oxide layer of the alloy containing yttrium or rare earth elements and also shows that the enriched concentration
of yttrium or lanthanum is detected within the chromium oxides which exist near the oxide scale/alloy matrix interface. Yttrium
or rare earth element oxides serve as the sites for the protective chromium oxide scales. 相似文献
4.
The formation of fiber-matrix interfacial reaction zone and its impact on mechanical properties of Gr/201 Al composite (41
vol pct fiber) was evaluated in the as-received condition and after heat treatment in vacuum at 450°C, 500°C, and 545°C temperatures
for one day, and at 545°C for one week. After heat treatment the microstructures of matrix and interface were studied by transmission
electron microscopy. This study revealed the presence of interfacial constituents Al4C3, Al4O4C, and TiB2. The mean fiber-matrix reaction zone thickness showed an increase with increasing heat treatment temperature and time. The
effects of heat treatment on interfacial shear strength, monotonic and cyclic tension/compression properties were evaluated.
The results show that the interfacial shear strength not only depends on chemical reaction but also depends on the thickness
of the reaction zone. An increase in reaction zone size reduces mechanical bonding considerably (thermal induced stresses).
The growth of reaction zone was very detrimental to monotonic and cyclic tension/tension fatigue behavior. The mechanism of
failure in tension/tension fatigue was the initiation of cracks at the interface and their subsequent propagation in the matrix.
It was concluded that the reaction zone was the controlling factor in tension/tension fatigue. In contrast, the results showed
that compressional fatigue was matrix dependent and was little sensitive to the size of the fiber/matrix interfacial reaction
zone. 相似文献
5.
The effect of aging at elevated temperature on interfacial stability and fatigue behavior of a SCS-6/Ti-22Al-23Nb “orthorhombic”
(O) titanium aluminide composite is investigated. The composite was heat treated in vacuum at 900 °C for up to 250 hours to
change the microstructural characteristics. The stability of the matrix alloy and interfacial reaction zone after extended
thermal exposure was analyzed. The effect of interface on fatigue behavior, including stiffness degradation, evolution of
fatigue damage, and crack growth rates, was characterized. Finally, a modified shear-lag model was used to predict the saturated
matrix crack spacing in the composite under fatigue loading. The results demonstrate that aging at elevated temperature affects
the stability of the interfacial reaction zone, which, in turn, degrades the fatigue properties of the composite. However,
fatigue crack will not develop from the ruptured interfacial reaction layer until the thickness of the reaction zone or the
maximum applied stress exceeds a critical value. 相似文献
6.
Experiments on the reaction between graphite and liquid Fe-Ti alloys were performed with a mirror furnace on board an airplane
during parabolic flights. Small Fe-Ti alloy samples were melted in contact with graphite and held for some seconds at a temperature
of 1550 °C. The samples were melted and solidified during a microgravity period. Carbon and titanium atoms reacted in the
melt and titanium carbides were formed. In the experiments, a precipitation zone with faceted titanium carbide crystals dispersed
in high carbon Fe-C-Ti alloy matrix was obtained near the graphite/alloy interface. The thicknesses of the carbide precipitation
zones were measured and effects of alloy composition on the growth rates of the carbide zones were revealed by experiments
and calculations. It was shown that the process was controlled by the diffusion of titanium in the liquid at low titanium
concentrations and by diffusion of carbon through the precipitation layer at high titanium concentrations in the melt. Supersaturation
of the carbide in front of the reaction interface was predicted from the calculations. The analysis showed that homogeneous
nucleation of titanium carbide can readily occur in the alloys. Carbide morphologies were analyzed, and the mechanisms which
lead to their formation are discussed. 相似文献
7.
The tensile behavior of aluminum matrix composites reinforced with 8 and 20 pet SiC whiskers or paniculate was characterized.
Two matrix alloys were employed, a solution-hardened Al-Mg alloy (5456) and a precipitation-hardened Al-Cu-Mg alloy (2124).
The precipitation-hardened alloy was aged to develop a variety of precipitate microstructures. It was found that additions
of SiC caused monotonie increases in the elastic modulus, 0.2 pct offset yield stress, work-hardening rate, and ultimate tensile
stress. The proportional limit, however, was found to first decrease and then increase with SiC content. Whiskers caused a
greater increase in the longitudinal elastic modulus than particles. For the 2124 alloy, it was found that the proportional
limit could be varied between 60 and 650 MPa by changing the precipitate microstructure, while changes in the SiC content
had much smaller effects. These observations are discussed in relation to current theories of the strengthening of short fiber
composites, with primary emphasis being placed on the effects of SiC additions on the elastic modulus and the work-hardening
rate. 相似文献
8.
Sapphire-reinforced NiAl matrix composites with chromium or tungsten as alloying additions were synthesized using casting
and zone directional solidification (DS) techniques and characterized by a fiber pushout test as well as by microhardness
measurements. The sapphire-NiAl(Cr) specimens exhibited an interlayer of Cr rich eutectic at the fiber-matrix interface and
a higher interfacial shear strength compared to unalloyed sapphire-NiAl specimens processed under identical conditions. In
contrast, the sapphire-NiAl(W) specimens did not show interfacial excess of tungsten rich phases, although the interfacial
shear strength was high and comparable to that of sapphire-NiAl(Cr). The postdebond sliding stress was higher in sapphire-NiAl(Cr)
than in sapphire-NiAl(W) due to interface enrichment with chromium particles. The matrix microhardness progressively decreased
with increasing distance from the interface in both DS NiAl and NiAl(Cr) specimens. The study highlights the potential of
casting and DS techniques to improve the toughness and strength of NiAl by designing dual-phase microstructures in NiAl alloys
reinforced with sapphire fibers.
R. TIWARI, formerly Research Associate, Department of Chemical Engineering, Cleveland State University 相似文献
9.
The age-hardening precipitation reaction in aluminum matrix composites reinforced with discontinuous alumina fibers was studied
using the differential scanning calorimetry (DSC) technique, microhardness tests, and transmission electron microscopy (TEM)
observation. Composites fabricated with the 2024 alloy matrix were infiltrated through a ceramic preform using a squeeze-casting
process. The alumina fibers had a considerable effect on the aging response of the matrix alloy in composites. Alumina fibers
caused suppression of Guinier—Preston (GP) zone formation in composite that reduced the peak hardening during artificial aging.
The suppression of GP zone formation in composites is believed to be due to the fiber-matrix interface, which acts as a sink
for vacancies during quenching. Moreover, the presence of reinforcement does not alter the kinetics of the subsequent artificial
aging of these Al2O3/2024Al composites. 相似文献
10.
《Acta Metallurgica Materialia》1990,38(4):551-559
Small additions of carbon and ZrB2 have been introduced into an FeAl alloy in order to obtain homogeneous distributions of different dispersoid particles in the B2 matrix. The carbon additions have produced the formation of second phase particles with a complex cubic structure (perovskite). The influence of these particles on the room and high temperature yield strength of the intermetallic has been compared to that of the ZrB2 particles. Tensile tests of these alloys have been performed between 25°C both types of particles produced a substantial increase, only the ZrB2 particles retain much of this strength at 600°C. The much faster decrease of stregth with temperature observed in the carbon containing alloy is explained in terms of a deformation process where the perovskite particles constitute a composites material with the matrix deforming at different rates. 相似文献
11.
A. Foroughi M. Shamanian M. Kasiri-Asgarani J. Kangazian 《Transactions of the Indian Institute of Metals》2018,71(3):533-544
In the present research, microstructure and mechanical properties of 2205 duplex stainless steel/A517 quench and tempered low alloy steel dissimilar joint were investigated. For this purpose, gas tungsten arc welding was used with ER2209 filler metal. Characterizations were conducted by optical microscopy, scanning electron microscopy equipped with an energy dispersive spectroscopy and X-ray diffraction. Mechanical properties were evaluated in micro-hardness, tensile and impact tests. Microstructure in the weld zone included an austenitic continuous network in the matrix of primary ferrite. No brittle phases were formed in the weld metal and stainless steel heat affected zone (HAZ). The weld metal/A517 interface showed higher hardness than other regions. Tensile tests indicated that the values of the yield and tensile strength were 663 and 796 MPa, respectively. Impact tests indicated that the weld zone had almost the same impact energy as base metals. The minimum impact energy of 12 J was related to A517 HAZ. The results of scanning electron microscopy for fracture surfaces indicated that weld zone, 2205 HAZ and A517 HAZ had ductile, ductile–brittle and brittle fracture mode, respectively. 相似文献
12.
A. Bedolla-Jacuinde M. W. Rainforth I. Mejía 《Metallurgical and Materials Transactions A》2013,44(2):856-872
This work analyzes the effect of different additions of silicon (0 to 5.0 pct) on the structure of a high-Chromium white cast iron, with chromium content of 16.8 pct and carbon 2.56 pct. The alloys were analyzed in both as-cast and heat-treated conditions. Casting was undertaken in metallic molds that yielded solidification rates faster than in commercial processes. Nevertheless, there was some degree of segregation of silicon; this segregation resulted in a refinement in the microstructure of the alloy. Silicon also generated a greater influence on the structure by destabilizing the austenitic matrix, and promoted greater precipitation of eutectic carbides. Above 3 pct silicon, pearlite formation occurred in preference to martensite. After the destabilization heat treatment, the matrix structure of the irons up to 3 pct Si consisted of secondary carbides in a martensitic matrix with some retained austenite; higher Si additions produced a ferritic matrix. The different as-cast and heat-treated microstructures were correlated with selected mechanical properties such as hardness, matrix microhardness, and fracture toughness. Silicon additions increased matrix microhardness in the as-cast conditions, but the opposite phenomenon occurred in the heat-treated conditions. Microhardness decreased as silicon content was increased. Bulk hardness showed the same behavior. Fracture toughness was observed to increase up to 2 pct Si, and then decreased for higher silicon contents. These results are discussed in terms of the effect of eutectic carbides’ size and the resulting matrix due to the silicon additions. 相似文献
13.
G. Das 《Metallurgical and Materials Transactions A》1990,21(6):1571-1578
Results on several aspects of a SiC fiber-reinforced IMI-829 (α-titanium alloy) metal matrix composite (MMC) are presented.
Scanning Auger microscopy (SAM) of SiC fibers reveals a high concentration of oxygen which varies across the diameter of the
fibers. It also shows that composition of SiC changes across the diameter and, for the most part, is carbon-rich nonstoichiometric
SiC. Transmission electron microscopy (TEM) of thin MMC foils shows the presence of TiC and TiSi2 in the reaction zone. Postfabrication thermal exposures of MMC s at 975 °C lead to void formation in the reaction zone. Concentration
profiles of various elements across the reaction zone reveal a buildup of Zr, Nb, and Si and a decrease of Ti, Al, and Sn
in the matrix around the reaction zone. Void formation in the reaction zone has been explained by the relatively high flow
of Si atoms to the matrix leading to an accumulation of vacancies in the reaction zone which condense to form voids. In addition,
an enhancement of hardness in the matrix around the reaction zone has been attributed to a strengthening of the matrix by
solid solution and precipitation hardening, together with a contribution from residual stresses.
This paper is based on a presentation made in the symposium “Interfaces and Surfaces of Titanium Materials” presented at the
1988 TMS/AIME fall meeting in Chicago, IL, September 25–29, 1988, under the auspices of the TMS Titanium Committee. 相似文献
14.
Comparison of orthorhombic and alpha-two titanium aluminides as matrices for continuous SiC-reinforced composites 总被引:1,自引:0,他引:1
P. R. Smith J. A. Graves CG. Rhodes 《Metallurgical and Materials Transactions A》1994,25(6):1267-1283
The attributes of an orthorhombic Ti aluminide alloy, Ti-21Al-22Nb (at. pct), and an alpha-two Ti aluminide alloy, Ti-24Al-11Nb
(at. pct), for use as a matrix with continuous SiC (SCS-6) fiber reinforcement have been compared. Foil-fiber-foil processing
was used to produce both unreinforced (“neat”) and unidirectional “SCS-6” reinforced panels. Microstructure of the Ti-24A1-11Nb
matrix consisted of ordered Ti3Al (α
2) + disordered beta(β), while the Ti-21 Al-22Nb matrix contained three phases: α2, ordered beta (β
0), and ordered orthorhombic(O). Fiber/ matrix interface reaction zone growth kinetics at 982 °C were examined for each composite system. Although both systems
exhibited similar interface reaction products(i.e., mixed Ti carbides, silicides, and Ti-Al carbides), growth kinetics in theα
2 +β matrix composite were much more rapid than in theO +β
0 +α
2 matrix composite. Additionally, interfacial reaction in theα
2 +β} composite resulted in a relatively large brittle matrix zone, depleted of beta phase, which was not present in theO +β
0+α
2 matrix composite. Mechanical property measurements included room and elevated temperature tensile, thermal stability, thermal
fatigue, thermo-mechanical fatigue (TMF), and creep. The three-phase orthorhombic-based alloy outperformed the α2+β alloy in all of these mechanical behavioral areas, on both an absolute and a specific(i.e., density corrected) basis. 相似文献
15.
采用光学显微镜(OM)、扫描电子显微镜(SEM)、纳米力学探针、力学性能测试以及室温摩擦磨损实验研究了Cu–(Fe–C)合金的铸态组织、形变态组织、Fe–C相形貌、力学性能和摩擦磨损行为。结果表明,Cu–(Fe–C)合金中弥散分布着微米级和纳米级的Fe–C相,其中微米级的Fe–C相在淬火和回火过程中发生了固态转变,这种固态转变与钢中的马氏体转变和回火转变类似。合金先在850 ℃淬火,然后在200、400和650 ℃回火,Fe–C相由针状马氏体逐渐向颗粒状回火索氏体转变,Fe–C相纳米硬度分别为9.4、8、4.2和3.8 GPa,实现了对强化相硬度的控制。室温摩擦磨损实验结果表明,随着回火温度升高,合金的磨损机制逐渐由犁削向黏着磨损和大塑性变形转变,导致合金的耐磨损性能降低。这一结论可以为通过Fe–C相的固态转变的方法调控Cu–(Fe–C)合金的摩擦磨损性能提供参考作用。 相似文献
16.
In the current work, a general methodology was proposed to demonstrate how to calculate the work of adhesion in a reactive multicomponent alloy/ceramic system. Applying this methodology, the work of adhesion of Al alloy/SiC systems and the influence of different alloying elements were predicted. Based on the thermodynamics of interfacial reaction and calculation models for component activities, the equilibrium compositions of the melts in Al alloy/SiC systems were calculated. Combining the work of adhesion models for reactive metal/ceramic systems, the work of adhesion in Al alloy/SiC systems both before and after the reaction was calculated. The results showed that the addition of most alloying elements, such as Mg, Si, and Mn, could increase the initial work of adhesion, while Fe had a slightly decreasing effect. As for the equilibrium state, the additions of Cu, Fe, Mn, Ni, Ti, and La could increase the equilibrium work of adhesion, but the additions of Mg and Zn had an opposite effect. Si was emphasized due to its suppressing effect on the interfacial reaction. 相似文献
17.
利用外约束型模拟空间热循环温度场试验设备对1420Al-Li合金焊缝进行了热循环(77~393K)试验,测量了热循环前后焊缝的拉伸性能,并观察了热循环前后焊缝的显微组织,讨论了热循环对焊缝组织和拉伸性能的影响。试验结果表明,经1000次或3000次热循环后,焊缝的强度和延伸率显著降低。热应力使焊缝显微组织产生损伤,主要表现为从晶界处向晶内发射位错,在晶界处形成位错塞积群,晶粒内位错密度逐渐升高。随着热循环次数的增加,组织损伤的不断累积导致在晶界处产生的应力集中程度增大,这是导致合金焊缝强度和延伸率下降的主要原因。 相似文献
18.
利用外约束型模拟空间热循环温度场试验设备对1420Al-Li合金焊缝进行了热循环(77~393 K)试验,测量了热循环前后焊缝的拉伸性能,并观察了热循环前后焊缝的显微组织,讨论了热循环对焊缝组织和拉伸性能的影响.试验结果表明,经1000次或3000次热循环后,焊缝的强度和延伸率显著降低.热应力使焊缝显微组织产生损伤,主要表现为从晶界处向晶内发射位错,在晶界处形成位错塞积群,晶粒内位错密度逐渐升高.随着热循环次数的增加,组织损伤的不断累积导致在晶界处产生的应力集中程度增大,这是导致合金焊缝强度和延伸率下降的主要原因. 相似文献
19.
Influence of Zn Coating on Interfacial Reactions and Mechanical Properties During Laser Welding-Brazing of Mg to Steel 总被引:1,自引:0,他引:1
Liqun Li Caiwang Tan Yanbin Chen Wei Guo Xinbin Hu 《Metallurgical and Materials Transactions A》2012,43(12):4740-4754
To investigate the influence of Zn coating on the joining of magnesium alloy AZ31?to Zn-coated steel, dissimilar metal joining both with and without Zn coating was performed by the laser welding-brazing (LWB) process. Welding characteristics including joint appearance, identification of interfacial reaction layers, and mechanical properties were comparatively studied. The results indicated that the presence of Zn coating promoted the wetting of liquid filler wire on the steel substrate. Heterogeneous interfacial reaction layers formed along the interface between the Mg alloy and Zn-coated steel, whereas no distinct reaction layer and increased concentration of Al were identified at the interface between the Mg alloy and noncoated steel. The maximum tensile-shear strength of Mg/steel lap joint with Zn coating reached 180?N/mm, which was slightly higher than that achieved without Zn coating (160?N/mm). Failure of joint in both cases occurred at the interface; however, the fracture mode was found to differ. For Zn-coated steel, the crack propagated along the Mg-Zn reaction layer and Fe-Al phase, with little Mg-Zn reaction phases remaining on the steel side. As for noncoated steel, some remnants of the seam adhered to the steel substrate. 相似文献
20.
G. N. Maniar J. E. Bridge H. M. James G. B. Heydt 《Metallurgical and Materials Transactions B》1970,1(1):31-42
Various authors have invoked coherency strains and disregistry between the crystal lattices of the matrix and γ′ phase to account for considerable hardening in γ′-strengthened superalloys. Hagel and Beattie correlated the mode of precipitation with the degree of its lattice mismatch. Heydt and Whitney used this approach during the development of an Fe-Ni base high temperature alloy. To understand the role of such a relationship, an investigation of a few experimental Ni-base/Fe-Ni base alloys was carried out. These alloys were strengthened by variable titanium, aluminum, and molybdenum additions and contained chromium. Lattice parameters of the solution treated and aged samples were measured. The γ′ phase was electrolytically extracted for lattice parameter determinations, and γ?γ′ mismatch calculated. The γ?γ′ mismatch calculated. The γ?γ′ mismatch was correlated with room temperature hardness and stress rupture properties at 1200°F. The influence of alloying additions, matrix and γ′ lattice parameters were interrelated. 相似文献