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1.
P. N. Adler R. L. Schulte E. J. Schneid E. A. Kamykowski F. J. Kuehne 《Metallurgical and Materials Transactions A》1980,11(9):1617-1623
The change in hydrogen concentration as a function of applied strain has been studied in commercial titanium alloys that included
threeβ-phase, twoα-phase, and an (α + β)-phase Ti-6Al-4V alloy with differingα/β morphologies.Insitu measurements were made using a nondestructive nuclear technique on samples for which uniaxial compressive and tensile stresses
were applied by four-point bending.
Theβ-phase alloys exhibited hydrogen redistribution under an elastic stress gradient, but no further change was discernible accompanying
plastic deformation. The extent of hydrogen concentration change for theβ-phase alloys was of the order of 4 to 6 pct for a 620 MPa stress gradient. This is less than would be predicted based on
available data for the partial molal volume of hydrogen. Diffusion coefficients in a stress gradient were also determined
and are consistent with those measured inβ-phase titanium at elevated and room temperatures. Within the experimental sensitivities there was no evidence of hydrogen
redistribution with applied stress for theα-phase and Ti-6Al-4V alloys. 相似文献
2.
3.
The effect of plastic deformation mode on tensile properties of quenched commercial β-phase titanium alloys has been investigated
at approximately constant grain size and oxygen content. In addition, stability of β-phase has been estimated from ω-reflections
or diffuse streaking in electron diffraction patterns in a manner similar to the previous works on binary β-phase titanium
alloys. Dominant mode of plastic deformation is 332 〈113〉 twinning in the alloys with large instability of β-phase, such as
Ti-ll.5Mo-6Zr-4.5Sn and Ti-15Mo-5Zr, and is crystallographic slip in the alloys with small instability of β-phase, such as
Ti-15Mo-5Zr-3Al, Ti-3Al-8V-6Cr-4Mo-4Zr, Ti-15V-3Cr-3Al-3Sn, Ti-8Mo-8V-2Fe-3Al, and Ti-13V-11Cr-3Al. Twinning leads to low
yield strength and large elongation, while slip results in high yield strength and small elongation in agreement with binary
and ternary β -phase titanium alloys. 相似文献
4.
Jeoung Han Kim S. L. Semiatin You Hwan Lee Chong Soo Lee 《Metallurgical and Materials Transactions A》2011,42(7):1805-1814
The flow behavior of the α and β phases in Ti-6Al-4V was interpreted in the context of a self-consistent modeling formalism. For this purpose, high-temperature
compression tests were conducted at various temperatures for a single-phase α alloy (Ti-7Al-1.5V), a variety of near-β alloys, and the two-phase alloy Ti-6Al-4V, each with an equiaxed microstructure. The flow behavior of the α phase in Ti-6Al-4V was deduced from the experimental results of the single-phase α alloy. The flow behavior of the β phase, which was predicted by using the self-consistent approach and the measured flow behaviors of Ti-6Al-4V and Ti-7Al-1.5V,
showed good agreement with direct measurements of the various near-β alloys. From these results, it was shown that the strength of the α phase is approximately three times higher than that of the β phase at temperatures between 1088 K and 1223 K (815 °C and 950 °C). It was also concluded that the relative strain rates
in the two phases varies significantly with temperature. The usefulness of the approach was confirmed by comparing the predicted
and measured flow stresses for other Ti-6Al-4V and near-α alloys. 相似文献
5.
J. R. Kennedy P. N. Adler H. Margolin 《Metallurgical and Materials Transactions A》1993,24(1):2763-2771
The effect of alloy composition on hydrogen activity was measured for seven titanium alloys as a means to determine the tendency
for hydrogen migration within dissimilar metal welds. The alloys were: Ti-CP, Ti-3A1-2.5V, Ti-3Al-2.5V-3Zr, Ti-3Al-2Nb-lTa,
Ti-6A1, Ti-6A1-4V, and Ti-6Al-2Nb-lTa-0.8Mo. Hydrogen pressure—hydrogen concentration relationships were determined for temperatures
from 600 °C to 800 °C and hydrogen concentrations up to approximately 3.5 at. pct (750 wppm). Fusion welds were made between
Ti-CP and Ti-CP and between Ti-CP and Ti-6A1-4V to observe directly the hydrogen redistribution in similar and dissimilar
metal couples. Hydrogen activity was found to be significantly affected by alloying elements, particularly Al in solid solution.
At a constant Al content and temperature, an increase in the volume fraction of β reduced the activity of hydrogen in α-β
alloys. Activity was also found to be strongly affected by temperature. The effect of temperature differences on hydrogen
activity was much greater than the effects resulting from alloy composition differences at a given temperature. Thus, hydrogen
redistribution should be expected within similar metal couples subjected to extreme temperature gradients, such as those peculiar
to fusion welding. Significant hydrogen redistribution in dissimilar alloy weldments also can be expected for many of the
compositions in this study. Hydride formation stemming from these driving forces was observed in the dissimilar couple fusion
welds. In addition, a basis for estimating hydrogen migration in titanium welds, based on hydrogen activity data, is described. 相似文献
6.
The effect of plastic deformation mode on tensile properties of quenched commercial β-phase titanium alloys has been investigated
at approximately constant grain size and oxygen content. In addition, stability of β-phase has been estimated from ω-reflections
or diffuse streaking in electron diffraction patterns in a manner similar to the previous works on binary β-phase titanium
alloys. Dominant mode of plastic deformation is {332}<113> twinning in the alloys with large instability of β-phase, such
as Ti-11.5Mo-6Zr-4. 5Sn and Ti-15Mo-5Zr, and is crystallographic slip in the alloys with small instability of β-phase, such
as Ti-15Mo-5Zr-3Al, Ti-3Al-8V-6Cr-4Mo-4Zr, Ti-15V-3Cr-3Al-3Sn, Ti-8Mo-8V-2Fe-3Al, and Ti-13V-11C-3Al. Twinning leads to low
yield strength and large elongation, while slip results in high yield strength and small elongation in agreement with binary
and termary β-phase titanium alloys. 相似文献
7.
Radhakrishna B. Bhat Seshacharyulu Tamirisakandala Daniel B. Miracle Vilupanur A. Ravi 《Metallurgical and Materials Transactions A》2005,36(3):845-857
The thermomechanical response of Ti-6Al-4V modified with 2.9 pct B produced by a blended powder metallurgy route was studied
with isothermal constant strain-rate hot compression tests in the temperature range 850 °C to 1200 °C and strain rate range
10−3 to 10 s−1. Detailed analyses of the flow stress data were conducted to identify various microstructural deformation and damage mechanisms
during hot working by applying available materials modeling techniques. In the α + β phase field, cavitation at the matrix/TiB interfaces and TiB particle fracture occurs at low strain rates (<10−1 s−1), while adiabatic shear banding also occurs at high strain rates. At low strain rates, the β phase deforms superplastically due to the stabilization of a fine grain size by the TiB particles. Grain boundary and matrix/TiB
interface sliding with simultaneous diffusional accommodation are observed to contribute to the β superplasticity. The deformation behavior at high strain rates in the β-phase field is similar to that of the α + β phase field, with microstructural manifestations of extensive cavitation at the matrix/TiB interfaces and TiB particle fracture. 相似文献
8.
The present study compares the fatigue and fracture properties of the high-strength β titanium alloy β-Cez with the conventional α+β titanium alloy Ti-6Al-4V, because of increasing interest in replacing α+β titanium alloys with β titanium alloys for highly stressed airframe and jet engine components. This comparison study includes the Ti-6Al-4V alloy
in an α+ β-processed condition (for a typical turbine blade application) and the β-Cez alloy in two distinctly different α+β-processed and β-processed conditions (optimized for a combination of superior strength, ductility, and fracture toughness). The comparison
principally showed a much lower yield stress for Ti-6Al-4V (915 MPa) than for both β-Cez conditions (1200 MPa). The Ti-6Al-4V material also showed the significantly lower high-cycle fatigue strength (resistance
against crack initiation) of 375 MPa (R=−1) as compared to the β-Cez alloy (∼600 MPa, R=−1). Particularly in the presence of large cracks (>5 mm), the fatigue crack growth resistance and fracture toughness of
the Ti-6Al-4V material is superior when compared to both β-Cez conditions. However, for small crack sizes, the conditions of both the alloys under study show equivalent resistance
against fatigue crack growth. For the β-Cez material, where microstructures were optimized for high fracture toughness (conventional large crack sizes) by thermomechanical
processing, maximum K
Ic-values of 68 MPa√m of the β-processed β-Cez condition (tested in the longitudinal direction) decreased by ∼50 pct in the presence of small cracks (1 mm). A similar
decrease in fracture toughness was obtained by loading the β-processed β-Cez condition perpendicular to the flat surfaces of the pancake-shaped β grain structure (tested in the short transverse direction). These results were discussed in terms of the effectiveness of
the crack front geometry in hindering crack propagation. Further, the results of this study were considered for alloy selection
and optimized microstructures for fatigue and fracture critical applications. Finally, the advantage of the α+β-processed β-Cez condition in highly stressed engineering components is pointed out because of its overall superior combination of fatigue
crack initiation and propagation resistance (especially against small fatigue cracks). 相似文献
9.
Bing Ye Marc R. Matsen David C. Dunand 《Metallurgical and Materials Transactions A》2012,43(1):381-390
A powder-level, finite-element model is created to describe densification, as a function of applied stress during uniaxial
hot pressing, of CP-Ti and Ti-6Al-4V powders with spherical or spheroidal shapes for various packing geometries. Two cases
are considered: (1) isothermal densification (in the α- or β-fields of CP-Ti and in the β-field of Ti-6Al-4V) where power-law creep dominates and (2) thermal cycling densification (across the α/β-phase transformation of Ti-6Al-4V) where transformation mismatch plasticity controls deformation at low stresses. Reasonable
agreement is achieved between numerical results and previously published experimental measurements and continuum modeling
predictions. 相似文献
10.
D. A. Meyn 《Metallurgical and Materials Transactions B》1974,5(11):2405-2414
The fracture toughness and resistance to inert-environment sustained load crack propagation of α-β titanium alloys are usually reduced by increased hydrogen contents. The range of hydrogen contents over which either fracture
toughness or threshold stress intensity for sustained load cracking was observed to decrease with hydrogen content is small
(0 to 50 ppm) for Ti-6 Al-4 V, but further increases in hydrogen content can cause an increase in cracking rates. Sustained
load crack propagation is characterized by a mixture of microvoid coalescence with cleavage, usually on a plane 12 to 15 deg
from {0001} of the hep α phase with some {000l} cleavage. Cleavage apparently initiates ahead of the main crack front within
a grains, usually near apparent α-β interfaces. Atmospheric moisture is inert with respect to sustained load cracking, that is, it does not cause stress corrosion
cracking. Sustained load cracking was demonstrated in Ti-8 Al-1 Mo-1 V, Ti-6 Al-6 V-2 Sn, and several grades of Ti-6 Al-4
V. 相似文献
11.
J. R. Kennedy P. N. Adler H. Margolin 《Metallurgical and Materials Transactions A》1993,24(12):2763-2771
The effect of alloy composition on hydrogen activity was measured for seven titanium alloys as a means to determine the tendency
for hydrogen migration within dissimilar metal welds. The alloys were: Ti-CP, Ti-3A1-2.5V, Ti-3Al-2.5V-3Zr, Ti-3Al-2Nb-lTa,
Ti-6A1, Ti-6A1-4V, and Ti-6Al-2Nb-lTa-0.8Mo. Hydrogen pressure-hydrogen concentration relationships were determined for temperatures
from 600 ‡C to 800 ‡C and hydrogen concentrations up to approximately 3.5 at. pct (750 wppm). Fusion welds were made between
Ti-CP and Ti-CP and between Ti-CP and Ti-6A1-4V to observe directly the hydrogen redistribution in similar and dissimilar
metal couples. Hydrogen activity was found to be significantly affected by alloying elements, particularly Al in solid solution.
At a constant Al content and temperature, an increase in the volume fraction ofΒ reduced the activity of hydrogen in α-@#@ Β alloys. Activity was also found to be strongly affected by temperature. The effect of temperature differences on hydrogen
activity was much greater than the effects resulting from alloy composition differences at a given temperature. Thus, hydrogen
redistribution should be expected within similar metal couples subjected to extreme temperature gradients, such as those peculiar
to fusion welding. Significant hydrogen redistribution in dissimilar alloy weldments also can be expected for many of the
compositions in this study. Hydride formation stemming from these driving forces was observed in the dissimilar couple fusion
welds. In addition, a basis for estimating hydrogen migration in titanium welds, based on hydrogen activity data, is described. 相似文献
12.
Although Ti-6A1-4V displays extensive superplasticity at 1200 K, lower superplastic forming temperatures are desirable. A
study was conducted with the goal of modifying the composition of the Ti-6A1-4V alloy to lower the optimum superplastic forming
temperature. Computer modeling results and previous experimental data suggested that additions to Ti-6A1-4V of beta-stabilizing
elements which have high diffusivity in the beta-phase would permit lower superplastic forming temperatures. A series of modified
alloys with 2 wt pct additions of Fe, Co, and Ni was prepared for experimental evaluation. The modified alloys achieved desirable
microstructures for superplasticity at 1088 K,i.e., the grain size was approximately 5 μm and roughly equal volume fractions of the alpha- and beta-phases were present at the
deformation temperature. The superplastic properties of the modified alloys were measured at 1088 K and 1144 K. The modified
alloys produced values of flow stress, strain rate sensitivity, and total elongation at 1088 K approaching those of the base
Ti-6A1-4V alloy at its standard superplastic forming temperature of 1200 K. In addition to lowering the superplastic forming
temperature, the β-stabilizing additions also increased room temperature strength levels above those normally found for Ti-6A1-4V.
Based on the room temperature and elevated temperature tensile properties, addition of selected beta-stabilizing elements
to Ti-6A1-4V simultaneously raises resistance to deformation at room temperature and lowers resistance to deformation at elevated
temperatures. This reversal in behavior is explained by considering the effect of beta-stabilizer additions on the deformation
mechanisms at room temperature and at elevated temperatures. 相似文献
13.
Observations have been made of cracking which develops after small plastic strains in the Ti-6Al-2Sn-4Zr-6Mo and Ti-6A1-4V
alloys at α-@#@ β interfaces, and a long slip band in α. Hydrogen and surface stresses and heat treat condition,i.e., solution treated or solution treated and aged have been ruled out. Cracking is attributed to intense slip commencing at
the α-@#@ β interfaces, and progressing into the α, or at martensite-matrix interfaces. 相似文献
14.
The effect of deformation-induced transformation on the fracture toughness of commercial titanium alloys 总被引:2,自引:0,他引:2
M. Niinomi T. Kobayashi I. Inagaki A. W. Thompson 《Metallurgical and Materials Transactions A》1990,21(6):1733-1744
The effect of deformation-induced transformation of metastableβ phase on the ductility and toughness of four commercial titanium alloys was investigated. Tensile tests, Charpy impact tests,
and both static and dynamic fracture toughness tests were carried out at temperatures between 77 and 473 K on four titanium
alloys containing metastableβ phase. Deformation-inducedα″ (orthorhombic martensite) was observed in an (α + β)-type Ti-6Al-2Sn-4Zr-6Mo alloy. The dynamic fracture toughness of this
alloy increased considerably at 223 K compared to those at other temperatures. In another (α + β)-type Ti-6A1-4V alloy, the
static fracture toughness at 123 K and the dynamic fracture toughness at 223 K were increased considerably by the presence
of deformation-induced martensite compared to those at other temperatures. The strength increased as the temperature decreased
in this alloy. An abnormal elongation of aβ-type alloy, Ti-15V-3Al-3Sn-3Cr, at 123 K was attributed to the mechanical twinning of theβ phase. However, the effect of deformation-induced transformation on the fracture toughness of Ti-3Al-8V-6Cr-4Mo-4Zr alloy
was not observed.
Formerly Visiting Associate Professor, Department of Metallurgical Engineering and Materials Science, Carnegie Mellon University,
Pittsburgh, PA.
Formerly with the Department of Production Systems Engineering, Toyohashi University of Technology. 相似文献
15.
Dale J. McEldowney Seshacharyulu Tamirisakandala Daniel B. Miracle 《Metallurgical and Materials Transactions A》2010,41(4):1003-1015
The Ti-6Al-4V (Ti-64) alloys modified with two levels of boron (1B and 1.7B (wt pct)) representing hypoeutectic and hypereutectic
compositions, produced via a prealloyed powder metallurgy approach, were subjected to various standard heat treatments of Ti-64 to study the microstructural
evolution and its influence on tensile properties. Boron-modified Ti-64 (Ti-64B) alloys exhibited differences in microstructural
response to heat treatment compared to that of Ti-64 due to variations in constituent phase fractions and the influence of
TiB on the beta-to-alpha phase transformation kinetics. The tensile elastic modulus of Ti-64B alloys increased nearly linearly
with the boron content (or TiB volume fraction) and the increase could be satisfactorily predicted with an isostrain rule
of mixtures (ROMs) and the Halpin–Tsai model. The Ti-64-1B possessed a good combination of tensile strength (1200 to1370 MPa)
and ductility (10 to 13 pct), while Ti-64-1.7B exhibited high strength (1300 to 1695 MPa) and modest ductility (2 to 3.5 pct).
Coarse primary TiB particles present in Ti-64-1.7B were found to initiate premature failure. Strength modeling revealed that
load sharing by the micron-sized TiB whiskers provides the major contribution for the increase in yield strength. 相似文献
16.
J. S. Marte T. F. Zahrah S. L. Kampe 《Metallurgical and Materials Transactions A》2004,35(5):1603-1611
A series of in-situ, deformation-processed metal matrix composites were produced by direct powder extrusion of blended constituents. The resulting
composites are comprised of a metallic Ti-6Al-4V matrix containing dispersed and co-deformed discontinuously reinforced-intermetallic
matrix composite (DR-IMC) reinforcements. The DR-IMCs are comprised of discontinuous TiB2 particulate within a titanium trialuminide or near-γ Ti-47Al matrix. Thus, an example of a resulting composite would be Ti-6Al-4V+40 vol pct (Al3Ti+30 vol pct TiB2) or Ti-6Al-4V+40 vol pct (Ti-47Al+40 vol pct TiB2), with the DR-IMCs having an aligned, high aspect ratio morphology as a consequence of deformation processing. The degree
to which both constituents deform during extrusion has been examined using systematic variations in the percentage of TiB2 within the DR-IMC, and by varying the percentage of DR-IMC within the metal matrix. In the former instance, variation of
the TiB2 percentage effects variations in relative flow behavior; while in the latter, varying the percentage of DR-IMC within the
metallic matrix effects changes in strain distribution among components. The results indicate that successful co-deformation
processing can occur within certain ranges of relative flow stress; however, the extent of commensurate flow will be limited
by the constituents’ inherent capacity to plastically deform. 相似文献
17.
Hiroaki Matsumoto Sadao Watanabe Naoya Masahashi Shuji Hanada 《Metallurgical and Materials Transactions A》2006,37(11):3239-3249
The Young’s modulus of Ti-V and Ti-V-Sn alloys quenched from the β-phase region after solution treatment and cold rolling
was investigated in relation to alloy compositions, microstructures, and constituent phases. The composition dependence of
the Young’s modulus for quenched Ti-V binary alloys shows two minima of 69 GPa at Ti-10 mass pct V and 72 GPa at Ti-26 mass
pct V. Between the two compositions, athermalω or stress-induced ω is introduced in retainedβ phase and increases Young’s modulus. That is, a low Young’s modulus is attained unless alloys undergoω transformation. In Ti-5 and -8 mass pct V, which under goα′ (hcp) martensitic transformation on quenching, the Young’s modulus further decreases by cold rolling, which can be reasonably
explained by the formation ofα′ rolling texture. Comparing Young’s modulus in Ti-V binary alloy with that in Ti-Nb binary alloy, it is found that Young’s
modulus is remarkably increased by athermal- or stress inducedω phase, and it shows a minimum when both martensitic andω transformation are suppressed during quenching in metastableβ alloys. The Sn addition to Ti-V binary alloy retards or suppresses athermal and stress-inducedω transformation, thereby decreasing Young’s modulus. Young’s modulus exhibits minimum values of 51 GPa in quenched (Ti-12
pct V)-2 pct Sn and of 57 GPa in cold-rolled (Ti-12 pct V)-6 pct Sn. 相似文献
18.
The strong dependence of the superplastic behavior of metals and alloys on grain size has been demonstrated, and it is now
well known that a fine grain size is normally a requirement for superplasticity. However, the microstructure of certain alloy
systems such as Ti-6A1-4V cannot always be adequately characterized by a single parameter such as grain size. In two-phase
α β alloys such as Ti-6A1-4V, other microstructural parameters such as volume fractions of the two phases, grain aspect ratio,
grain size distribution and crystallographic texture may also influence superplasticity. For example, if “grain switching”
is an important deformation mechanism in superplastic flow as suggested by Ashby and Verall, then factors such as grain aspect
ratio and range of grain sizes would be expected to have an effect on superplastic behavior. In this study, these microstructural
features were determined for several different heats of Ti-6Al-4V, and the corresponding superplastic properties were evaluated
in terms of their fully characterized microstructure. The flow stress as a function of strain rate, strain rate sensitivity
exponent (m) as a function of strain rate and total elongation on properties were found to be strongly influenced by microstructural
parameters such as grain aspect ratios, grain size and grain size distribution. 相似文献
19.
C G. Rhodes A. K. Ghosh R. A. Spurling 《Metallurgical and Materials Transactions A》1987,18(12):2151-2156
Ti-6Al-4V-2Ni is being considered as a composite matrix material because of its potential for a lower consolidation temperature
and reduced reaction product formation compared with conventional Ti-6A1-4V. Stress/strain-rate measurements of Ti-6Al-4V-2Ni
in sheet form provided data for calculation of diffusion bonding parameters required for efficient consolidation. These data
were used as consolidation parameters for fabrication of SiC (SCS-6) reinforced Ti-6Al-4V-2Ni. The composite with 10.5 vol
pct SiC exhibits room temperature tensile strength approximately 80 pct of that observed for conventional Ti-6Al-4V/SiC having
35 to 40 vol pct SiC. Scanning and transmission electron microscopy revealed that the fiber-matrix reaction zone is roughly
one-half the thickness of that found in SiC-reinforced Ti -6A1-4V, and that it consists of TiC and Ti5Si3. Nickel does not enter into the reaction zone products, but rather promotes the formation of Ti2Ni in the matrix. 相似文献
20.
Friction-stir (FS) processing was used to modify the coarse, fully lamellar microstructure of investment cast and hot isostatically
pressed (HIP’ed) Ti-6Al-4V. The effect of FS processing on mechanical properties was investigated using microtensile and four-point
bend fatigue testing. The tensile results showed a typical microstructure dependence where yield strength and ultimate tensile
strength both increased with decreasing slip length. Depending on the processing parameters, fatigue strength at 107 cycles was increased by 20 pct or 60 pct over that of the investment cast and HIP’ed base material. These improvements have
been verified with a statistically significant number of tests. The results have been discussed in terms of the resistance
of each microstructure fatigue crack initiation and small crack propagation. For comparison, a limited number of fatigue tests
was performed on α + β forged Ti-6Al-4V with varying primary α volume fraction and also on investment cast material heat treated to produce a bi-lamellar condition. 相似文献