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1.
The Al
x
CoCrCuFeNi alloys with multiprincipal elements ( x=the aluminum content in molar ratio, from 0 to 3.0) were synthesized using a well-developed arc-melting and casting method,
and their mechanical properties were investigated. These alloys exhibited promising mechanical properties, including excellent
elevated-temperature strength and good wear resistance. With the addition of aluminum from x=0 to 3.0, the hardness of the alloys increased from HV 133 to 655, mainly attributed to the increased portion of strong bcc
phase to ductile fcc phase, both of which were strengthened by the solid solution of aluminum atoms and the precipitation
of nanophases. The alloys exhibited superior high-temperature strengths up to 800 °C, among which the Al 0.5CoCrCuFeNi alloy, especially, had enhanced plasticity and a large strain-hardening capacity. Moreover, the wear resistance
of these alloys was similar to that of ferrous alloys at the same hardness level, while the alloys with lower hardness exhibited
relatively higher resistance because of their large strain-hardening capacity. 相似文献
2.
The authors studied the effect of vanadium addition on the microstructure and properties of Al 0.5CoCrCuFeNi high-entropy alloy. The microstructure of Al 0.5CoCrCuFeNiV
x
( x=0 to 2.0 in molar ratio) alloys was investigated by scanning electron microscopy, energy dispersive spectrometry, and X-ray
diffraction. With little vanadium addition, the alloys are composed of a simple fcc solid-solution structure. As the vanadium
content reaches 0.4, a BCC structure appears with spinodal decomposition and envelops the FCC dendrites. From x=0.4 to 1.0, the volume fraction of bcc structure phase increases with the vanadium content increase. When x=1.0, fcc dendrites become completely replaced by bcc dendrites. Needle-like σ-phase forms in bcc spinodal structure and increases
from x=0.6 to 1.0 but disappears from x=1.2 to 2.0. The hardness and wear resistance of the alloys were measured and explained with the evolution of the microstructure.
The hardness values of the alloys increase when the vanadium content increases from 0.4 to 1.0 and peak (640 HV) at a vanadium
content of 1.0. The wear resistance increases by around 20 pct as the content of vanadium increases from x=0.6 to 1.2 and levels off beyond x=1.2. The optimal vanadium addition is between x=1.0 and 1.2. Compared with the previous investigation of Al 0.5CoCrCuFeNi alloy, the vanadium addition to the alloy promotes the alloy properties. 相似文献
3.
A new approach for the design of alloy systems with multiprincipal elements is presented in this research. The Al
x
CoCrCuFeNi alloys with different aluminum contents ( i.e., x values in molar ratio, x=0 to 3.0) were synthesized using a well-developed arc-melting and casting method. These alloys possessed simple fcc/bcc structures,
and their phase diagram was predicted by microstructure characterization and differential thermal analyses. With little aluminum
addition, the alloys were composed of a simple fcc solid-solution structure. As the aluminum content reached x=0.8, a bcc structure appeared and constructed with mixed fcc and bcc eutectic phases. Spinodal decomposition occurred further
on when the aluminum contents were higher than x=1.0, leading to the formation of modulated plate structures. A single ordered bcc structure was obtained for aluminum contents
larger than x=2.8. The effects of high mixing entropy and sluggish cooperative diffusion enhance the formation of simple solid-solution
phases and submicronic structures with nanoprecipitates in the alloys with multiprincipal elements rather than intermetallic
compounds. 相似文献
4.
The effect of Ni content on microstructure, hardness, and wear resistance was studied for the Cr 13Ni 5Si 2-base intermetallic alloys toughened by Ni-base solid solution ( γ). Volume fraction and microhardness of the Cr 13Ni 5Si 2 primary dendrite as well as the average hardness of the Cr 13Ni 5Si 2/ γ alloy decrease with the increasing Ni content. The Cr 13Ni 5Si 2/ γ alloys have excellent wear resistance under dry sliding wear test conditions, which increases under high contact load wear
conditions and decreases under low contact load wear test conditions with the increasing Ni content. The high wear resistance
is due to the combination of high toughness of γ and high hardness of Cr 13Ni 5Si 2 and formation of a transferred cover layer on the worn surface during wear process. The wear rate of the Cr 13Ni 5Si 2/ γ alloy is governed by the slow process of microspalling or pullout of the cracked Cr 13Ni 5Si 2 primary dendrites. The Cr 13Ni 5Si 2/ γ alloys have extremely low load sensitivity of wear and the load-sensitivity coefficient of wear decreases drastically as
the Ni content increases. 相似文献
5.
New economical duplex stainless steels (DSSs) containing 19Cr-6Mn- xNi-1.0Mo-0.5W-0.5Cu-0.2N ( x = 0.5 to 2.0) were developed, and the microstructure, impact property, and corrosion resistance of the alloys were studied.
The ferrite content increases with the solution treatment temperature, but decreases with an increase in nickel. The sigma
phase is not found precipitating in the alloys treated with solution from 1023 K to 1523 K (750 °C to 1250 °C). The low-temperature
impact energy of the experimental alloys increases first and then decreases rapidly with an increase in nickel, which is mainly
due to the martensite transformation with an increase in austenite. The alloys have a better mechanical property and pitting
corrosion resistance than AISI 304. Among the designed DSS alloys, 19Cr-6Mn-1.3Ni-1.0Mo-0.5W-0.5Cu-0.2N is found to be an
optimum alloy with proper phase proportion, a better combination of mechanical strength and elongation, and higher pitting
corrosion resistance compared with those of the other alloys. 相似文献
6.
The present study is concerned with γ-(Ti 52Al 48) 100−x
B
x
( x=0, 0.5, 2, 5) alloys produced by mechanical milling/vacuum hot pressing (VHPing) using melt-extracted powders. Microstructure
of the as-vacuum hot pressed (VHPed) alloys exhibits a duplex equiaxed microstructure of α 2 and γ with a mean grain size of 200 nm. Besides α 2 and γ phases, binary and 0.5 pct B alloys contain Ti 2AlN and Al 2O 3 phases located along the grain boundaries and show appreciable coarsening in grain and dispersoid sizes during annealing
treatment at 1300 °C for 5 hours. On the other hand, 2 pct B and 5 pct B alloys contain fine boride particles within the γ
grains and show minimal coarsening during annealing. Room-temperature compressing tests of the as-VHPed alloys show low ductility,
but very high yield strength >2100 MPa. After annealing treatment, mechanically milled alloys show much higher yield strength
than conventional powder metallurgy and ingot metallurgy processed alloys, with equivalent ductility to ingot metallurgy processed
alloys. The 5 pct B alloy with the smallest grain size shows higher yield strength than binary alloy up to the test temperature
of 700 °C. At 850 °C, 5 pct B alloy shows much lower strength than the binary alloy, indicating that the deformation of fine
5 pct B alloy is dominated by the grain boundary sliding mechanism.
This article is based on a presentation made in the symposium “Mechanical Behavior of Bulk Nanocrystalline Solids,” presented
at the 1997 Fall TMS Meeting and Materials Week, September 14–18, 1997, in Indianapolis, Indiana, under the auspices of the
Mechanical Metallurgy (SMD), Powder Materials (MDMD), and Chemistry and Physics of Materials (EMPMD/SMD) Committees. 相似文献
7.
Recently, (Fe-Co)-B-Si-Nb bulk metallic glasses (BMGs) were produced. Such BMGs exhibit high glass-forming ability (GFA) as
well as good mechanical and magnetic properties. These alloys combine the advantages of functional and structural materials.
The soft magnetic properties can be enhanced by nanocrystallization. To force the nanocrystallization, small content of Cu
was added to the starting composition. In this article, {[(Fe 0.5Co 0.5) 0.75Si 0.05B 0.20] 0.96Nb 0.04} 100–x
Cu
x
glassy alloys ( x = 1, 2, and 3) were chosen for investigation. The GFA and the thermal stability of these alloys were evaluated. The effects
of crystallization during heat-treatment processes on the phase evolution and the magnetic properties, including M
s
, H
c
, and T
c
, in these alloys were investigated. The phase analyses were done with the help of the X-ray diffraction patterns recorded
in situ by using the synchrotron radiation in transmission configuration. 相似文献
8.
The structure, hydrogen storage property, and electrochemical characteristics of the La 0.7Mg 0.3Ni 5.5−x
(Al 0.5Mo 0.5)
x
( x=0, 0.2, 0.4, 0.6, 0.8) hydrogen storage alloys have been investigated systematically. It has been found by X-ray powder diffraction
and Rietveld analysis that the alloys are multiphase and consist of impurity Ni phase and two main crystallographic phases,
namely, the La(La, Mg) 2Ni 9 phase and the LaNi 5 phase, and the lattice parameters and the cell volumes of both the La(La, Mg) 2Ni 9 phase and the LaNi 5 phase increase with increasing Al and Mo content in the alloys. The P-C isotherm curves indicated that the hydrogen storage
capacity of the alloy first increases and then decreases with increasing x, and the equilibrium pressure decreases with increasing x. The electrochemical measurements show that the maximum discharge capacity first increases from 298.5 ( x=0) to 328.3 mAh/g ( x=0.6) and then decreases to 304.7 mAh/g ( x=0.8). The high rate dischargeability (HRD) of the alloy electrodes increases lineally from 65.4 pct ( x=0) to 86.6 pct ( x=0.8) at the discharge current density of 1200 mA/g. Moreover, the exchange current density of the alloy electrodes also increases
monotonously with increasing x by the linear polarization curves. The hydrogen diffusion coefficient in the alloy bulk, D, increases with increasing Al and Mo content and thus enhances the low-temperature dischargeability (LTD) of the alloy electrodes. 相似文献
9.
Porous titanium (Ti) and its alloys are promising materials for orthopedic applications due to their low elastic modulus, high strength, excellent corrosion resistance, and biocompatibility. In this study, the porous Ti–xNb–5Ag (x = 25, 30 and 35 wt%) alloys were synthesized using the powder metallurgy approach. The effects of Nb content on the porosity, mechanical properties, and electrochemical corrosion behavior of the alloys were investigated. XRD analysis revealed that the porous alloys mainly consist of α-Ti, β-Ti, intermetallic compound (Ti4Nb), and oxides of TiO2 and NbO phases. Porous alloys possess the porosity ranging from 57 to 65%, due to the addition of NH4HCO3 (45 wt%). Increase in Nb content lead to a reduction in the elastic modulus and compression strengths of the sintered porous Ti–xNb–5Ag alloys. All three developed porous Ti–xNb–5Ag alloys show the optimum combination of elastic modulus and compression strength, which is suitable for orthopedic applications. These porous alloys exhibit excellent electrochemical corrosion resistance in the simulated body fluids, and the samples having low porosity exhibit higher corrosion resistance than high-porosity samples. 相似文献
10.
Alloys of Co 78-x
Pt
x
B 10Si 12 were produced using the melt-spin process in order to study the crystallization behavior and ensuing magnetic properties
of the Co-Pt amorphous alloys as a function of the Pt content. We showed that when x>15, well below its stoichiometric composition, CoPt intermetallic compound crystallized in the amorphous alloy. Below this
composition, the main crystallization product was Co with Pt dissolved in its lattice. The nucleation of CoPt greatly altered
the crystallized microstructures and magnetic properties of the Co-Pt amorphous alloys during annealing. In spite of the nucleation
of CoPt with its high magnetic anisotropy, the highest coercivity was obtained when x was 15, free of the CoPt grains. It was also concluded that the Pt addition, in general, triggered crystallization to occur
at a progressively lower temperature. 相似文献
11.
β-Titanium alloys form one of the most versatile classes of structural materials due to their high specific strength, good hardenability, crack propagation resistance and substantial ductility. β-Titanium alloy with a composition (in wt%) of Ti–5Al–5Mo–5V–1Cr–1Fe was processed by double vacuum arc remelting route. In the present work, the effect of boron addition (up to 0.12 wt%) on the as-cast microstructure and β-transus (T β) of the alloy was studied using characterization tools like optical microscopy, electron back scattered diffraction, scanning electron microscopy, differential scanning calorimetry (DSC) and dilatometry. It was observed that boron addition has resulted in refinement of the as-cast microstructure due to precipitation of titanium boride whiskers along the grain boundaries. The DSC and dilatometry studies on the as-cast alloy revealed significant effect of boron addition on thermal stability of the alloy. 相似文献
12.
High-entropy alloys (HEAs) are a new class of alloys having equiatomic ratios of alloying elements in their composition. Boron is an important element that can increase the strength of steels and wear resistance of hard facing coatings with its high hardness compounds. The effect of boron (B) in FeNiCoCrCu-based HEAs has not been studied in detail to date. In the current study, the microstructural and mechanical properties of FeNiCoCrCuBx HEAs with varying boron contents (x = 1, 2, 3, 4, 5 at. pct) were investigated using specimens prepared by two-stage processing (sintering and vacuum arc melting). Microstructural and structural studies were carried out using optical microscopy, scanning electron microscopy, electron probe microanalysis, X-ray diffraction, and differential scanning calorimetry. Vickers microhardness and three-point bending tests were also performed to observe the variations in mechanical properties. Results showed that the microstructures of HEAs are generally dendritic and contain two different FCC phases, i.e., Fe-Ni-Co-Cr-rich dendritic and Cu-rich interdendritic phases. The hardness values increased with increasing B content with a maximum hardness of 337 HV. According to three-point bending test results, the highest strength of about 1900 MPa and good ductility were obtained with HEA-3 (3 at. pct B). 相似文献
13.
The influence of the content of reaction- and surface-active alloying elements (rare-earth metals (REMs)) and the method of
their introduction into cast high-temperature γ′-Ni 3Al-based intermetallic alloys, which are thermally stable natural eutectic composites, on their structure-phase state and
the mechanical properties is studied. The life of low-alloy heterophase γ′ + γ cast high-temperature light Ni 3Al-based alloys is shown can be increased at temperatures exceeding 0.8 T
m
( T
m
is the melting temperature of Ni3Al) due to additional stabilization of the single-crystal structure of these alloys with
submicron and nanometer-sized particles of the phases formed by refractory and active REMs. It is also shown that stage-by-stage
fractional introduction of all components into alloys during vacuum induction melting with allowance for their reaction activities
(most refractory metals are introduced in the form of low-melting-point master alloys at the first stage of vacuum induction
melting, and lanthanum is introduced with a master alloy in the optimal contents of 0.1–2 wt % into the charge of VKNA-1V
and VKNA-25 alloys at the final stage) leads to the formation of a modified structure stabilized by nanoprecipitates of nickel
and aluminum lanthanides and the phases formed by refractory metals. This method increases the life of VKNV-1V-type alloys
(0.5 wt % Re) at 1000–1200°C by a factor of ∼1.7 and that of VKNA-25-type alloys (1.2 wt % Re and Co) by a factor of ∼3. 相似文献
14.
Ni 3Si alloys with 20, 30, and 40 wt pct Cr were fabricated by self-propagating high-temperature synthesis casting at 543 K. Thermite
reaction (Cr 2O 3+5CrO 3+12Al=7Cr+6Al 2O 3) was used in Cr alloying. The method is simple and economical when used to prepare Ni 3Si-based alloys. The process is described in detail. The alloys were analyzed with X-ray diffraction (XRD) and scanning electron
microscopy (SEM) with X-ray energy dispersive spectroscopy (EDS). The results showed the alloys mainly consisted of Ni 3Si and Ni 5Si 2 with dissolved Cr and Cr phases. Phases and microstructures of the alloys varied with Cr content. Microhardness, bending
and compressive strength, and wear rate of the alloys were measured. Microhardness of the alloys was higher than that of Ni 3Si without Cr and increased with Cr content. Bending and compressive strength of the alloys were better than those of the
Ni 3Si without Cr, and those of the alloy with 30 wt pct Cr were the highest. The wear rate of the alloys was lower than that
of the Ni 3Si without Cr and decreased with Cr content. 相似文献
15.
A new Fe-Cr-Al (FCA) alloy system has been developed with good oxidation resistance and creep strength at high temperature. The alloy system is a candidate for use in future fossil-fueled power plants. The creep strength of these alloys at 973 K (700 °C) was found to be comparable with traditional 9 pct Cr ferritic–martensitic steels. A few FCA alloys with general composition of Fe-30Cr-3Al-.2Si- xNb ( x = 0, 1, or 2) with a ferrite matrix and Fe 2Nb-type Laves precipitates were prepared. The detailed microstructural characterization of samples, before and after creep rupture testing, indicated precipitation of the Laves phase within the matrix, Laves phase at the grain boundaries, and a 0.5 to 1.5 μm wide precipitate-free zone (PFZ) parallel to all the grain boundaries. In these alloys, the areal fraction of grain boundary Laves phase and the width of the PFZ controlled the cavitation nucleation and eventual grain boundary ductile failure. A phenomenological model was used to compare the creep strain rates controlled by the effects of the particles on the dislocations within the grain and at grain boundaries. (The research sponsored by US-DOE, Office of Fossil Energy, the Crosscutting Research Program). 相似文献
16.
Effect of titanium and nickel on the structure and properties of Fe 3Al intermetallic alloy containing about 1.0wt.% C have been investigated. The composition of the alloying element was substituted
for Iron. The alloys were prepared by melting commercial grade raw materials iron, aluminum, titanium or nickel in air induction
furnace with flux cover (AIMFC). Further these ingots were refined by electroslag refining (ESR) process. These ingots could
be successfully hot-worked using conventional hot-forging and hot-rolling techniques. The hot-worked material was sound and
free from cracks. ESR hot-rolled alloys were examined using optical microscopy, X-ray diffraction (XRD), scanning electron
micrograph (SEM) to understand the microstructure of these alloys. The electron probe micro analysis (EPMA) studies were carried
out to determine the matrix and precipitate compositions and to identify the phases present in the alloys. The base alloy
and the alloy containing Ni exhibited a two-phase microstructure of Fe 3AlC 0.5 precipitates in Fe 3Al matrix. The alloy containing Ti exhibits three-phase microstructure, the additional phase being TiC precipitate. Ti addition
resulted in no improvement in strength at room temperature and at 873 K whereas Ni addition has resulted in greater improvement
in strength at room temperature and at 873 K and also improved the creep life significantly from 66 hrs to 111 hrs. 相似文献
17.
The high cycle fatigue behaviour of high boron polycrystalline Ni 3Al alloys is studied. A single phase Ni 3Al alloy with a mole fraction of 0.6% B and a Ni 3Al alloy containing a mole fraction of 1.0% B with a small amount of the boride eutectic at the grain boundaries are selected for investigation. High cycle fatigue tests at room temperature with R (minimum stress/maximum stress) 0.1 are conducted in air and at 30 Hz. The results show that the Ni 3Al(0.6% B) alloy is better than the Ni 3Al(1.0% B) alloy in the fatigue resistance, although, the latter is much higher than the former in static strengths. The fatigue fracture surfaces are observed by SEM. 相似文献
18.
Conclusions It has been established that the highest transverse rupture strength and wear resistance combined with the lowest coefficient of friction are shown by alloys of eutectic composition. In alloys of the TiN 0·9-TiB 2 system higher ductility during friction is exhibited by the boride phase, whose substructure experiences greater changes compared with the nitride phase. The greatest deformation during friction characterizes the phases in the TiN 0·73-TiB 2 alloy. The strengthening and strength loss processes at temperatures of 20–400°C are determined by the strength loss processes occurring in the boride phase, and those above 400°C, by the strengthening and strength loss processes taking place in the nitride phase.Translated from Poroshkovaya Metallurgiya, No. 2(242), pp. 70–76, February, 1983. 相似文献
19.
The need for structural materials with high-temperature strength and oxidation resistance coupled with adequate lower-temperature
toughness for potential use at temperatures above ∼1000 °C has remained a persistent challenge in materials science. In this
work, one promising class of intermetallic alloys is examined, namely, boron-containing molybdenum silicides, with compositions
in the range Mo (bal), 12 to 17 at. pct Si, 8.5 at. pct B, processed using both ingot (I/M) and powder (P/M) metallurgy methods.
Specifically, the oxidation (“pesting”), fracture toughness, and fatigue-crack propagation resistance of four such alloys,
which consisted of ∼21 to 38 vol. pct α-Mo phase in an intermetallic matrix of Mo 3Si and Mo 5SiB 2 (T 2), were characterized at temperatures between 25 °C and 1300 °C. The boron additions were found to confer improved “pest”
resistance (at 400 °C to 900 °C) as compared to unmodified molybdenum silicides, such as Mo 5Si 3. Moreover, although the fracture and fatigue properties of the finer-scale P/M alloys were only marginally better than those
of MoSi 2, for the I/M processed microstructures with coarse distributions of the α-Mo phase, fracture toughness properties were far superior, rising from values above 7 MPa √m at ambient temperatures to almost
12 MPa √m at 1300 °C. Similarly, the fatigue-crack propagation resistance was significantly better than that of MoSi 2, with fatigue threshold values roughly 70 pct of the toughness, i.e., rising from over 5 MPa √m at 25 °C to ∼8 MPa √m at 1300 °C. These results, in particular, that the toughness and cyclic
crack-growth resistance actually increased with increasing temperature, are discussed in terms of the salient mechanisms of
toughening in Mo-Si-B alloys and the specific role of microstructure. 相似文献
20.
Properties of pure metals can be enhanced by alloying with other metallic or non-metallic elements according to the need. However, as multiple alloying elements in an alloy may lead to the formation of many intermetallic compounds with complex microstructures and poor mechanical properties, new types of metallic alloys called high entropy alloys with at least five elements with equimolar ratios were developed. In this study, FeNiAlCuCrTi x Nb y ( x, y = 0, 0.5, 1.0, 1.5) alloys have been prepared using Ar arc melting technique. Microstructural studies using scanning electron microscope and XRD showed that Ti addition promoted secondary BCC 2 phase whereas, Nb acted as FCC stabilizer. Samples with combined Nb and Ti addition showed FCC 1 and FCC 2 structure with Nb-rich FCC 2 dendritic phase as dominant phase. Though, individual Nb and Ti additions have resulted in increased hardness, combined additions have resulted in highest hardness of 797 HV under 1 kg load. 相似文献
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