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1.
Effects of microalloying and ceramic particulates on mechanical properties of TiAl-based alloys 总被引:1,自引:0,他引:1
Micro-alloyed titanium aluminides and TiAl-based composite with a fully dense structure have been synthesized by a powder metallurgical method. X-ray diffraction and EDX studies show that the monolithic TiAl-based alloy and its composite consist of TiAl and Ti3Al compounds with the former as the major phase. Additions of Nb and/or (Mo + Cr) exert remarkable effects on the resultant phase compositions and mechanical properties of TiAl-based alloys. Both the added Mo and Cr elements are dissolved into the TiAl-based compounds to exhibit solid solution strengthening effect whereas Nb is only partially dissolved and the rest appears in the Nb-rich compound, Nb2Al. In general, the micro-alloyed TiAl and the composite exhibit superior flexural strength and fracture toughness to TiAl-based monolithic compound. 相似文献
2.
F.H.Froes College of Mines Earth Resources University of Idaho Moscow Idaho - USA) 《材料科学技术学报》1994,10(4):251-262
The production. characteristics. and commercialization of monolithic and composite titanium aluminides are summanzed with emphasis on use in the demanding aerospace industry. The attractive elevated temperature properties combined with alow density make these materials of great interest, but inherently low "forgiveness", and environmental concerns, must be overcome before widespread use will occur One synthesis method for the production of monolithic titanium aluminides-mechanical alloying- will be discussed in detail 相似文献
3.
V. I. Itin N. A. Shevchenko E. N. Korosteleva A. A. Tukhfatullin M. Z. Mirgazizov V. É. Gyunter 《Technical Physics Letters》1997,23(4):294-296
“Bioceramic-titanium nickelide” functional composites are proposed and investigated. It is shown that the incorporation of
an alloy (titanium nickelide) possessing superelasticity and shape memory enhances the strength properties of the composite
while the porosity through the material needed for the ingrowth of living tissue is maintained. These composites are biocompatible
and exhibit a property similar to the superelasticity characteristic of living tissue.
Pis’ma Zh. Tekh. Fiz. 23, 1–6 (April 26, 1997) 相似文献
4.
Computed and experimental data on the splitting failure of copper, nickel, titanium, molybdenum, brass, and bronze metallic
foils from 0.005 to 1 mm thick under thermal shock initiated by the x-radiation of a nuclear explosion are presented. It is
proposed that the concepts “average energy liberated over the thickness (mass) of the specimen” ε, “specific absorbed energy”
W, and “splitting strength of the material” σ be used as criterial characteristics of failure thresholds of optically thin
flat metallic specimens (foils). It is demonstrated that the critical average energy liberation ε*, which results in splitting, decreases logarithmically (ε* =A
*-B
*log Δ) with increasing thickness Δ of the irradiated specimens in the interval Δ≈0.001–1 mm, and the critical specific potential
energy W* reguired to effect splitting increases with increasing optical mass m of the specimen under the law W*=−αmlog (βm), where A*, B*, α, and β are certain parameters. It is shown that the longevity of the copper, nickel, titanium, molybdenum, brass, and
bronze under radiation-induced thermal shock decreases exponentially with increasing amplitude of the failing stress (splitting
strength) and can be described on the basis of the kinematic concept of strength.
Deceased.
Translated from Problemy Prochnosti, No. 1, pp. 37–47, January–February, 1997. 相似文献
5.
Summary In recent studies, the exact solutions of the Eshelby tensors for a spherical inclusion in a finite, spherical domain have
been obtained for both the Dirichlet- and Neumann boundary value problems, and they have been further applied to the homogenization
of composite materials [15], [16]. The present work is an extension to a more general boundary condition, which allows for
the continuity of both the displacement and traction field across the interface between RVE (representative volume element)
and surrounding composite. A new class of Eshelby tensors is obtained, which depend explicitly on the material properties
of the composite, and are therefore termed “the Composite Eshelby Tensors”. These include the Dirichlet- and the Neumann-Eshelby
tensors as special cases. We apply the new Eshelby tensors to the homogenization of composite materials, and it is shown that
several classical homogenization methods can be unified under a novel method termed the “Dual Eigenstrain Method”. We further
propose a modified Hashin-Shtrikman variational principle, and show that the corresponding modified Hashin-Shtrikman bounds,
like the Composite Eshelby Tensors, depend explicitly on the composite properties. 相似文献
6.
Laser consolidation (LC) developed by National Research Council’s Industrial Materials Institute (NRC-IMI-London) since mid-1990s,
is a laser cladding based rapid manufacturing and material additive process that could fabricate a “net-shape” functional
metallic shape through a “layer-upon-layer” deposition directly from a computer aided design model without using molds or
dies. In order to evaluate the LC processability of different materials, some representative nickel-based superalloys (IN-625,
IN-718, IN-738, and Waspaloy), stainless steels (austenitic SS316L and martensitic SS420), and lightweight alloys (Ti–6Al–4V
titanium alloy and Al-4047 aluminum alloy) have been investigated. Like other laser cladding based processes, due to process-induced
rapid directional solidification, the LC alloys have demonstrated certain unique morphological characteristics. Moreover,
the “as-consolidated” LC alloys, in nature, are in the “as-quenched” state, and some precipitation processes from their matrices,
which are sometimes critical to the development of mechanical performance of the materials, could be effectively suppressed
or retarded. Post-heat treatments, therefore, could necessarily facilitate the process of achieving their required operational
microstructures. In this article, a comprehensive investigation was performed including metallurgical soundness and process-induced
morphological characteristics of the LC materials, and microstructure development brought by post-LC heat treatments using
optical microscope, scanning electron microscope, and X-ray diffraction. The implications on the mechanical performance of
the LC materials were discussed as well in order to provide essential information for potential industrial applications of
the LC materials. 相似文献
7.
Popa MV Vasilescu E Drob P Vasilescu C Demetrescu I Ionita D 《Journal of materials science. Materials in medicine》2008,19(1):1-9
This paper studies the long-term (20,000 exposure hours) behavior of titanium and Ti–5Al–4V alloy—Carter–Brugirard saliva
interface and the short-term (500 exposure hours) resistance of titanium and Ti–5Al–4V alloy—Tani&Zucchi saliva interface.
Potentiodynamic polarization method was applied for the determination of the main electrochemical parameters. Linear polarization
measurements for to obtain the corrosion rates were used. Monitoring of the open circuit potentials (E
oc) for long-term have permitted to calculate the potential gradients due to the pH, ΔE
oc(pH) and to the saliva composition ΔE
oc(c) changes which can appear “in vivo” conditions and can generate local corrosion. Atomic force microscopy (AFM) has analyzed
the surface roughness. Ion release was studied by atomic absorption spectroscopy (AAS). In Carter–Brugirard saliva both titanium
and Ti–5Al–4V alloy present very stable passive films, long-term stability, “very good” resistance, low values of the open
circuit potential gradients, which cannot generate local corrosion. In Tani&Zucchi artificial saliva, pitting corrosion and
noble pitting protection potentials (which cannot be reached in oral cavity) were registered; titanium ion release is very
low; surface roughness increase in time and in the presence of the fluoride ions, denoting some increase in the anodic activity. 相似文献
8.
Baier RE 《Journal of materials science. Materials in medicine》2006,17(11):1057-1062
“Biomaterials” are non-living substances selected to have predictable interactions with contacting biological phases, in applications
ranging from medical/dental implants to food processing to control of biofouling in the sea. More than 30 years of empirical
observations of the surface behaviours of various materials in biological settings, when correlated with the contact-angle-determined
Critical Surface Tensions (CST) for these same materials, support the definition of the “theta surface”. The “theta surface”
is that characteristic expression of outermost atomic features least retentive of depositing proteins, and identified by the
bioengineering criterion of having measured CST between 20 and 30 mN/m. Biomaterials applications requiring strong bioadhesion
must avoid this range, while those requiring easy release of accumulating biomass should have “theta surface” qualities. Selection
of blood-compatible materials is a main example. It is forecast that future biomaterials will be safely and effectively translated
directly to clinical use, without requiring animal testing, based on laboratory data for CST, protein denaturation, and cell
spreading alone. 相似文献
9.
Work of adhesion influence on the rheological properties of silica filled polymer composites 总被引:4,自引:0,他引:4
As the work of adhesion, W
a, increases between a silica filler surface and a polymer matrix, the dynamic viscosity and the shear modulus of the composite
material increase. The logarithms of these properties decrease linearly as W
a decreases. At lower dynamic test frequencies, a change in W
a has a more dramatic impact on these properties than at higher frequencies. An “effective silica particle size” model can
be used to explain why W
a affects the viscosity and the shear modulus of a composite. According to that model, the thickness of the interphase layer
increases as the W
a increases. An increase in effective particle size decreases the “free” polymer volume, and the decrease free volume polymer
causes both the viscosity and the shear modulus to increase. Increasing the dynamic test frequency releases some of the immobilized
polymer from the filler surface which causes the effective particle size to decrease. As the effective particle size decreases
because of the increased testing frequency and approaches the mean size of the original filler, the impact of the W
a value on viscosity and shear modulus should decrease. However, the friction experienced between the filler interphase and
the polymer, the so called “skin friction”, depends on the magnitude of W
a and the more general term, bond energy density (BED). The skin friction determines the viscosity of the composite, particularly
at lower frequencies. Higher W
a values induce higher skin friction and thereby higher flow resistance (viscosity) as polymer chains move along the filler
surface. 相似文献
10.
We develop a mathematical model of microscopically inhomogencous but macroscopically isotropic materials with statistically
distributed components of tensors of stiffness and strength. In this model, the material is represented as the continuous
set of “characteristic” (i.e., typical of a given material) disjoint microscopic domains (microvolumes). The microinhomogeneous
material is identified with an “effectively homogeneous” material in such a way that, at the same points, the components of
the displacement vector determined for these materials are equal. It is assumed that, for each “characteristic” microvolume
the parameters of stiffness and strength of the material are constant and can be obtained as values of an arbitrary random
variable distributed according to the Weibull law and averaged over a certain random interval of any length. The components
of the tensor averaged as indicated above are also regarded as random variables distributed according to the normal law with
the same probability of hitting any arbitrarily located “characteristic” microvolume. The model is based on the assumption
that the material is isotropic both macroscopically and in any “characteristic” microvolume. The stress-strain state of the
microinhomogeneous material is described by the “effective” (averaged over its volume) components of the stress tensor. The
model takes into account cracks in the material if their length exceeds the size of the relevant “characteristic” volume.
The model is justified for the case of an infinite microinhomogeneous cracked plane under uniaxial tension. It is shown that
the parameters determining the stressed state of this plane are not independent in the vicinity of the crack tip. The relevant
constraints are given by equations of the model. The choice of these parameters which ignores the indicated constraints leads
to results contradicting well-known physical facts. By using the symmetry properties of the system under consideration and
physical reasoning, we obtain equations for the determination of the size of “characteristic” domains and physically reasonable
dependences of the maximal “effective” tensile stresses and their direction on the parameter of inhomogeneity of the material
and average volume of defects.
Karpenko Physicomechanical Institute, Ukrainian Academy of Sciences, Lviv. Pidstryhach Institute of Applied Problems in Mechanics
and Mathematics, Ukrainian Academy of Sciences, Lviv. Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 32, No.
4, pp. 5–16, July–August, 1996. 相似文献
11.
A novel hot-pressing technique for the manufacturing of basalt fibre reinforced glass matrix composites was investigated.
Two-dimensional (2D) fibre mats were sandwiched between borosilicate glass powder layers, thus configuring a much simpler
processing route than that commonly employed for the production of fibre-reinforced glasses. Besides economic benefits, the
use of fibre mats may lead to technologic advantages due to the possibility of readily coating the fibres with a suitable
material (e.g. titanium oxide) by means of the sol-gel method. The coating of basalt fibre mats with TiO2 is proposed for preventing the fibres from an excessive adhesion to the glass matrix. The developed composites containing
15 vol% of 2D-fibre reinforcement exhibited promising bending strength (∼90 MPa) and desirable “graceful” fracture behaviour
without catastrophic failure. Thus the present study represents a convenient approach for production of advanced low-cost
fibre reinforced glass matrix composites for structural applications. 相似文献
12.
Time dependent behavior of elements combining ultra-high performance fiber reinforced concretes (UHPFRC) and reinforced concrete 总被引:1,自引:1,他引:0
Structural elements combining Ultra-High Performance Fiber Reinforced Concretes (UHPFRC) and concrete offer a high potential
in view of rehabilitation and modification of existing structures. The investigation of the time-dependent behavior of composite
“UHPFRC-concrete” elements is a fundamental step in the determination of durability and serviceability. For this, an experimental
program was conducted on large composite “UHPFRC-concrete” beams and a numerical model was validated with the test results.
The experimental results and a parametric study performed with the numerical model showed that UHPFRC and normal strength
reinforced concrete are compatible in the long-term and that the critical period of composite “UHPFRC-concrete” elements are the first 90 days after the casting of the UHPFRC layer. Thus, the high potential
of such composite elements can be exploited also in the long term. 相似文献
13.
The relationship between the concepts of “error” and “uncertainty” of measurement results is examined. The concepts of “standard
uncertainty,” “combined standard uncertainty,” and “expanded uncertainty” are shown to be inapplicable in nonmetric scales
of quantities and properties, in which the general concept of “uncertainty” in the broad sense is recommended.
Translated from Izmeritel'naya Tekhnika, No. 5, pp. 29–30, May, 2000. 相似文献
14.
Geopolymer materials have been proposed for various applications due to their excellent fire resistance and low processing
cost. One requirement that geopolymer composites need to meet for structural applications is graceful failure, as catastrophic
failure during service can result in significant loss of life. In this paper, the properties of novel low cost composites
made by infiltrating stainless steel mesh with geopolymer resin are reported. Four point flexure tests on these composites
showed metal-like yielding behavior instead of catastrophic failure and the “yield strength” was significantly higher than
the flexure strength of the geopolymer matrix. Exposure to high temperatures, 800 and 1,050°C, resulted in the “yield strength”
decreasing to ∼59 and ∼44% level respectively compared to the strength of as-processed samples. However, the good ductility
was still retained after the high temperature treatment, which makes this novel composite a strong candidate for the applications
where catastrophic failure upon fire/high temperature exposure needs to be avoided. 相似文献
15.
《Materials Science & Technology》2013,29(4):308-316
AbstractProcessing routes for intermetallic based materials are briefly surveyed and compared. For monolithic intermetallics the two main factors determining process routes both derive from the low room temperature ductility of most intermetallics. They are the need to maintain material cleanness, thus reducing fracture initiation sites, and the desire to achieve fine grain size to seek to improve ductility. For the titanium based aluminides there is also a need to minimise interstitial, particularly oxygen, pick-up during processing. For intermetallic based composites, a broad range of processes is already being investigated. In many of these, issues of cleanness may be more difficult to control than for the monolithic composites. With continuous fibre reinforced composites a further process impetus is the need to control interfacial interactions between the fibre and the matrix.MST/1560 相似文献
16.
Static and cyclic fatigue crack growth behaviour of gamma base titanium aluminides with three different microstructures were
investigated. Influence of cyclic test frequency on fatigue crack growth behaviour was also studied at room temperature under
a controlled humidity condition. The crack growth behaviour both under static and cyclic loading was strongly influenced by
the microstructure. The threshold stress intensity and crack growth behaviour under cyclic loading were much inferior than
that under static loading indicating the ‘true-cyclic fatigue’ effect exhibited in gamma base titanium aluminides. No significant
effect of test frequency on the crack growth behaviour was observed for the equiaxed and duplex microstructure materials. 相似文献
17.
We investigate the wear resistance of VT14 titanium alloy after oxynitriding realized by modifying nonstoichiometric titanium
nitride by oxygen. It is shown that the oxide component in an oxynitride coating improves the wear resistance of the alloy
in a friction pair with BrAZh9-4l brass. It is established that the wear rate of a “VT14 titanium alloy with oxynitride coating–U8
steel” tribopair is an order smaller than that of a “VT14 titanium alloy with oxynitride coating–BrAZh9-4l brass” tribopair.
It is also established that the tribologic behavior of the former tribopair improves after replacing AMH-10 lubricant by I-40A
lubricant. 相似文献
18.
The present work considers the evaporation process ofNH
3 inNH
3/H2 atmosphere, that takes place in neutral gas absorption refrigeration units. The data obtained are used to calculate the “psychrometric
problem” and the evaporation process within an insulated tube. The “psychrometric problem” deals with the determination of
the mass fraction of theNH
3/H
2 gas mixture from known “dry” and “wet bulb” temperatures for Lewis numbers not equal to one. The results are in good agreement
with some existing experimental data. 相似文献
19.
Scientometric study of laser patent literature 总被引:3,自引:2,他引:1
An analysis of the patents filed and scientific papers published and abstracted in theJournal of Current Laser Abstracts (JCLA) for the period 1967–95 indicates that innovative activity in laser science and technology was at its peak in the early
70s. However, scientific activity surpassed the innovative activity in the early 80s. There was a continuous shift in emphasis
from “applications of lasers” to “experimental laser research” and to “theoretical laser research”. Further analysis of the
1840 patents field in 1970–71, 1975–76, and 1980–85 indicates that most of the firms filing patents were situated in USA and
thus USA is the leading country filing patents in this area followed by Japan. “Spectroscopy of laser output” followed by
“Communication applications of laser” got the maximum emphasis. 相似文献
20.
A correlation between the peculiarities of the electric permittivity (EP) ɛ(q, ω) of a homogenous and isotropic Coulomb system (CS) in the limit of ω → 0, q → 0 and q → 0, ω → 0 is established on the basis of exact limiting relations; general expression for static EP ɛ(q, 0) of a CS is obtained in the region of small wave vectors q. The concepts of a “true” dielectric and “ideal” conductor are introduced. The definition of a “true” screening radius is
considered. A critical point of two-component CS is shown to correspond to either the “true” dielectric state or the “ideal”
conductor one. 相似文献