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1.
Benda Yan Gregory C. Farrington Campbell Laird 《Metallurgical and Materials Transactions A》1985,16(6):1151-1157
We have studied the dislocation structures of single crystals of copper cycled in 0.1 M perchloric acid and under different
polarization potentials. TEM samples were cut from representative specimens both after saturation and after fracture. Although
much higher strain localization was observed in the crystals cycled at anodic potentials, the dislocation structures observed
were very similar to those of specimens tested at cathodic potentials and in air. For a plastic shear strain amplitude of
2×10−3, regular loop patches and dipolar walls were observed. For a higher strain amplitude of 4×10−3, dipolar walls associated with secondary slip were found in addition to regular primary walls. We believe this structure
to be associated with breaking the primary persistent slip bands (PSB's) into truncated groups, of which the truncations were
lined up along the traces of the secondary slip plane. Dislocation structures observed after final fracture of the crystals
were different from those formed by cycling just into saturation; dipolar walls formed first and cell structures developed
later. Thus, we confirmed the transition of dipolar walls into cells, reported by other investigators. Moreover, the transition
of loop patches into “rungs” structure, the embryo of the PSB, was also observed in the late stages of life.
BENDA YAN, formerly with the University of Pennsylvania 相似文献
2.
E. Frás A. Janas S. Wierzbiński H. F. Lopez 《Metallurgical and Materials Transactions A》2002,33(12):3831-3838
The deformation behavior of TiC particulate-reinforced aluminum composites (Al-TiC
p
) was investigated in this work using pure aluminum as the reference matrix material. Uniaxial compression tests were carried
out at 293 and 623 K and at two strain rates (3.7×10−4 and 3.7×10−3 s−1). Yield strengths of up to 127 MPa were found in composites containing 10 vol pct TiC particulates, which were almost 4 times
the yield strength of pure Al. In addition, at 623 K, relatively small reductions in yield strength were found, suggesting
that this property was rather insensitive to temperature for the temperatures investigated in this work. Nevertheless, at
623 K, increasing the rate of straining from 3.7×10−4 s−1 to 3.7×10−3 s−1 lowered the yield strength, particularly in 10 vol pct TiC
p
-Al composites. Two stages of work hardening were identified in pure Al and a 10 vol pct TiC
p
composite during plastic flow through the modified version of the Hollomon equation (σ = Kɛ
n ± Δ). In particular, the work-hardening exponents found in pure Al shifted from high to low values as the extent of plastic
strain was increased while the opposite was true for the 10 vol pct TiC
p
composite. Finally, at 623 K, dynamic recovery mechanisms became dominant at plastic strain levels >0.2 in 10 vol pct TiC
p
-Al composites, with the effect being minor at room temperature. 相似文献
3.
The defect microstructure at saturation of silver single crystals subjected to constant plastic strain amplitude, γp, fatigue tests in the range γp = ±0.0025 to ±0.025 was studied by transmission electron microscopy. The rate of fatigue hardening and the saturation stress
increase with increasing plastic strain amplitude. The dislocation microstructure at saturation changes from an open band
structure at small plastic strain amplitudes to a closed cell structure at large plastic strain amplitude. The defect microstructure
at saturation can be characterized by the density and distribution of point defect clusters and the dislocation wall spacing
along the primary Burgers vector direction. The saturation stress is inversely proportional to the dislocation wall spacing
along the primary Burgers vector direction and to the spacing of the point defect clusters on the primary slip plane. There
is no significant difference between the fatigue hardening, the cyclic stress-strain curve and the dislocation microstructure
at saturation of silver and copper single crystals. 相似文献
4.
G. Y. Kim L. M. He J. D. Meyer W. Y. Lee A. Quintero J. A. Haynes 《Metallurgical and Materials Transactions A》2004,35(11):3581-3593
A laboratory-scale chemical vapor deposition (CVD) reactor was used to perform “continuous” Hf doping experiments while the
surface of a single-crystal Ni alloy was being aluminized to form an aluminide (β-NiAl) coating matrix for 45 minutes at 1150 °C. The continuous doping procedure, in which HfCl4 and AlCl3 were simultaneously introduced with H2, required a high HfCl4/AlCl3 ratio (>∼0.6) to cause the precipitation of Hf-rich particles (∼0.1 μm) at grain boundaries of the coating layer, with the overall Hf concentration of ∼0.05 to 0.25 wt pct measured in the coating
layer by glow-discharge mass spectroscopy (GDMS). Below this ratio, Hf did not incorporate as a dopant into the growing coating
layer from the gas phase, as the coating matrix appeared to be “saturated” with other refractory elements partitioned from
the alloy substrate. In comparison, the Hf concentration in the aluminide coating layer formed on pure Ni was in the range
of ∼0.1 wt pct, which was close to the solubility of Hf estimated for bulk NiAl. Interestingly, the segregation of Hf and
the formation of a thin γ′-Ni3Al layer (∼0.5 μm) at the coating surface were consistently observed for both the alloy and pure-Ni substrates. The formation of the thin
γ′-Ni3Al layer was attributed to an increase in the elastic strain of the β-NiAl phase, associated with the segregation of Hf as well as other refractory alloying elements at the coating surface. This
phenomenon also implied that the coating layer was actually growing at the interface between the γ′-Ni3Al layer and the β-NiAl coating matrix, not at the gas/coating interface, during the early stage of the coating growth. 相似文献
5.
S. S. Hecker M. G. Stout K. P. Staudhammer J. L. Smith 《Metallurgical and Materials Transactions A》1982,13(4):619-626
The γ→α transformation in 304 stainless steel can be induced by plastic deformation at room temperature. The kinetics of strain-induced
transformations have been modeled recently by Olson and Cohen. We used magnetic techniques to monitor the progress of the
γ→α transformation in 304 stainless steel sheet loaded in uniaxial and biaxial tension at both low (10-3 per second) and high (103 per second) strain rates. We found that using the von Mises effective strain criterion gives a reasonable correlation of
transformation kinetics under general strain states. The principal effect of increased strain rate was observed at strains
greater than 0.25. The temperature increase resulting from adiabatic heating was sufficient to suppress the γ→α transformation
substantially at high rates. The consequences of the γ→α transformation on mechanical behavior were noted in uniaxial and
biaxial tension. Uniaxial tension tests were conducted at temperatures ranging from 50 to -80°C. We found that both the strain
hardening and transformation rates increased with decreasing temperature. However, the martensite transformation saturates
at ≈85 pct volume fraction α. This can occur at strains less than 0.3 for conditions where the transformation is rapid. Once
saturation occurs, the work hardening rate decreases rapidly and premature local plastic instability results. In biaxial tension,
the same tendency toward plastic instability associated with high transformation rates provides a rationale for the low biaxial
ductility of 304 stainless steel. 相似文献
6.
K.S. Chan J.W. Tian B. Yang P.K. Liaw 《Metallurgical and Materials Transactions A》2009,40(11):2545-2556
The evolution of slipbands into fatigue cracks in surface grains of commercially pure Ni, Ni200 (99.35Ni-0.4Fe-0.25Cu, in
wt pct), was studied at ambient temperature. Round-bar specimens with electropolished surfaces were fatigued under displacement-controlled,
fully reversed conditions at four strain amplitudes under a nominal strain rate of 1 × 10−3 s−1. Low-cycle fatigue tests were periodically interrupted to characterize the slip morphology at various fatigue cycles using
scanning electron microscopy. The results showed that the distribution of slip in Ni200 varied considerably in individual
surface grains at a given strain amplitude. Some grains were deformed more severely and exhibited more intense slipbands than
others, while some surface grains showed the absence of slip lines with no evidence of plastic deformation. The evolutions
of slipband width and spacing in deformed surface grains were followed as a function of fatigue cycles in order to assess
the slipband morphology at the onset of fatigue crack initiation. 相似文献
7.
Fully reversed low-cyclic fatigue (LCF) tests were conducted on [001], [012], [-112], [011], and [-114] oriented single crystals
of nickel-based superalloy DD3 with different cyclic strain rates at 950°C. The cyclic strain rates were chosen as 1.0×10−2, 1.33×10−3 and 0.33×10−3 s−1. The octahedral slip systems were confirmed to be activated on all the specimens. The experimental result shows that the
fatigue behavior depends on the crystallographic orientation and cyclic strain rate. Except [001] orientation specimens, it
is found from the scanning electron microscopy (SEM) examination that there are typical fatigue striations on the fracture
surfaces. These fatigue striations are made up of cracks. The width of the fatigue striations depends on the crystallographic
orientation and varies with the total strain range. A simple linear relationship exists between the width and total shear
strain range modified by an orientation and strain rate parameter. The nonconformity to the Schmid law of tensile/compressive
flow stress and plastic behavior existed at 950°C, and an orientation and strain rate modified Lall-Chin-Pope (LCP) model
was derived for the nonconformity. The influence of crystallographic orientation and cyclic strain rate on the LCF behavior
can be predicted satisfactorily by the model. In terms of an orientation and strain rate modified total strain range, a model
for fatigue life was proposed and used successfully to correlate the fatigue lives studied in this article. 相似文献
8.
《Acta Metallurgica Materialia》1994,42(5):1631-1638
Polycrystals of pure copper were cyclically deformed, at room temperature under symmetric tension-compression fatigue at constant total strain amplitude control with an approximate constant plastic strain rate of 10−4. The relationship between the saturation stress amplitude and strain amplitude over a range of plastic strain from 2 × 10−7 to 10−2 reveals three regions of cyclic hardening. A quasi-plateau, where the stresses show a slow constant increase, was observed in the intermediate region extending in the plastic strain range γpl, of 1.5 × 10−5 to 7.5 × 10−4. In this region, persistent slip bands (PSBs) which consist of “ladder” structures, similar to the case of single crystals, were found in the bulk of the fatigued polycrystals. The fatigue limit was found to be Δσs/2 = 73 MPa which corresponds to the plastic strain Δϵpl/2 = 1.5 × 10−5 where PSBs do not form. 相似文献
9.
The low cycle deformation saturation stress in Ferrovac-E a-iron was studied using diametral plastic strain (0.001 ≤ Δεdp/2 ≤ 0.0135) as the control variable. Increasing strain rate (6 × 10•5 s•1 • 4 × 10•3 s•1) and decreasing temperature (295 to 173 K) increased the saturation stress levels. The cyclic work hardening coefficient
decreased from 0.18 at 295 K to 0.10 at 173 K, which is consistent with previous studies of monotonie deformation. The temperature
dependence of both the saturation stress and the strain rate sensitivity, as measured during cyclic deformation, were similar
to that measured during monotonic tensile tests. The temperature dependence of the dislocation velocity indexm* was in good agreement with published values from high cycle fatigue and monotonie tensile tests. Thus the same deformation
mechanisms are believed to occur in both monotonie and large plastic cyclic deformation (Δεdp/2 ≥ 0.001) of a-iron. 相似文献
10.
Xiaolei Xu Liang Wang Zhiwei Yu Jianbing Qiang Zukun Hei 《Metallurgical and Materials Transactions A》2000,31(4):1193-1199
The microstructure of the low-temperature plasma-nitrided layer on AISI 304 austenitic stainless steel was studied by transmission
electron microscopy (TEM). The results show that the surface of the layer consists of a supersaturated solid solution (γ′N) based on the γ′-Fe4N phase whose electron diffraction pattern (EDP) has a strong diffuse scattering effect resulting from supersaturating nitrogen
(above 20 at. pct) and 〈110〉 streaks arising from matrix elastic strain due to the formation of paired or clustered Cr-N.
The latter is due to the N above the 20 at. pct γ′-Fe4N-phase value and leads to a lattice parameter that is greater than that of the γ′-Fe4N phase. The subsurface of the layer is composed of a supersaturated solid solution based on γ-austenite, which is an expanded austenite, γ
N. Its morphology shows the basketweave or “tweedlike” contrast consisting of so-called stacking fault precipitates having
twin relationships with the matrix whose EDP shows diffuse scattering streaks with certain directions. The ε martensite transformation was observed in the subsurface of the layer. The increase in stacking faults compared with the
original stainless steel and formation of ε martensite in the subsurface of the layer indicate that nitrogen lowers the stacking fault energy of austenite. 相似文献
11.
《Acta Metallurgica Materialia》1990,38(6):1191-1200
Transmission electron microscopy of boron-doped Ni3Al single crystals, oriented for single slip and cyclically deformed at room temperature, revealed a high density of dislocation dipoles and point defect clusters. Observations of circular perfect dislocation loops, Frank loops, vacancy tetrahedra and spherical voids provide evidence of vacancy condensation during fatigue cycling at room temperature. It is suggested that lattice misfit develops between persistent slip bands (PSB) and matrix as a result of the generation and coalescence of excess vacancies in PSBs. The misfit strain at PSB/matrix interfaces is considered to increase with increasing cumulative plastic strain. Together with SEM observations of surface topography, it is suggested that fatigue damage in Ni3Al single crystals is initiated by the formation of microvoids (microcracks) at PSB/matrix interfaces. The microvoids (microcracks) break down the coherency of the PSB/matrix interfaces and thereby relieve the accumulated misfit strain at the interfaces. A model of fatigue crack initiation based upon a surface energy criterion is proposed. 相似文献
12.
David M. Follstaedt James A. Knapp Samuel M. Myers 《Metallurgical and Materials Transactions A》2003,34(4):935-949
We have measured the yield strengths of Ni samples having high densities of nanometer-size precipitates. Surface layers containing
NiO or γ-Al2O3 precipitates were formed in Ni specimens by ion implanting O alone or O and Al, with subsequent annealing. The yield strengths
of the layers were obtained through nanoindentation in conjunction with finite-element simulations. The yield strengths of
the Ni alloys were combined with earlier data for O-implanted Al and compared to predictions of a recent treatment of the
Orowan mechanism, in which dislocations loop around precipitates and by-pass them. The strengths vary with changes in precipitate
microstructure, as predicted, and conform to the theory in absolute magnitude to within a factor of 1.5. This agreement extends
over broad microstructural ranges: precipitate sizes from ∼1 to 20 nm, volume fractions from 0.05 to 0.30, densities from
4×1016/cm3 to as high as ∼1020/cm3, edge-to-edge spacings as small as 1.4 nm, two precipitated phases, and two metal matrices with shear moduli differing by
a factor of 3. Ion implantation increases near-surface yield strengths to as high as 5 GPa, suggesting that this treatment
may be useful for hardening the surfaces of Ni components in micro-electromechanical systems. 相似文献
13.
Henning F. Poulsen Torben Lorentzen Yi-Lin Liu Robert Feidenhans’l 《Metallurgical and Materials Transactions A》1997,28(1):237-243
An X-ray technique for local measurements of the internal residual stress near inclusions in metalmatrix composites (MMCs)
is presented. The technique utilizes medium- to high-energy monochromatic X-rays from a synchrotron source and a combination
of slits on the entry and exit sides of the sample in order to determine the strains from small volumes deep within the composite
sample. The strains of the individual matrix grains are sampled and averaged, allowing for a much improved spatial resolution.
An analyzer is used in order to avoid well-known systematic errors related to geometry and stability of the beam. First results
are obtained on a model system consisting of a 500 μm continuous W fiber imbedded in an A1 matrix. Two specimens were investigated
with typical Al grain sizes of 1 mm and 30 μm. With a gage volume of 10×10×170 μm3, we obtained count rates on the order of 5000 cps and an accuracy in the strain measurements of Δε≤5×10−5. For both specimens, we found no variations of the radial and transverse strain components with the distance to the fiber,
indicating either a complete debonding of the system, a very weak interface, or interface deterioration due to chemical reaction.
Intragranular strain fluctuations on the order of ε=±10−4 were found to build up close to the grain boundaries. For the specimen with the smaller Al grain size, sampling data from
approximately 15 grains at the same distance to the fiber was sufficient for averaging out the intergranular fluctuations.
Finally, we observe effects from the conventional metallurgic sample preparation up to 400 μm from the surface, emphasizing
the relevance of bulk techniques. 相似文献
14.
M. Valsan D. H. Sastry K. Bhanu sankara Rao S. L. Mannan 《Metallurgical and Materials Transactions A》1994,25(1):159-171
Strain-rate effects on the low-cycle fatigue (LCF) behavior of a NIMONIC PE-16 superalloy have been evaluated in the temperature
range of 523 to 923 K. Total-strain-controlled fatigue tests were performed at a strain amplitude of ±0.6 pct on samples possessing
two different prior microstructures: microstructure A, in the solution-annealed condition (free of γ′ and carbides); and microstructure
B, in a double-aged condition with γ′ of 18-nm diameter and M23C6 carbides. The cyclic stress response behavior of the alloy was found to depend on the prior microstructure, testing temperature,
and strain rate. A softening regime was found to be associated with shearing of ordered γ′ that were either formed during
testing or present in the prior microstructure. Various manifestations of dynamic strain aging (DSA) included negative strain
rate-stress response, serrations on the stress-strain hysteresis loops, and increased work-hardening rate. The calculated
activation energy matched well with that for self-diffusion of Al and Ti in the matrix. Fatigue life increased with an increase
in strain rate from 3 × 10-5 to 3 × 10-3 s-1, but decreased with further increases in strain rate. At 723 and 823 K and low strain rates, DSA influenced the deformation
and fracture behavior of the alloy. Dynamic strain aging increased the strain localization in planar slip bands, and impingement
of these bands caused internal grain-boundary cracks and reduced fatigue life. However, at 923 K and low strain rates, fatigue
crack initiation and propagation were accelerated by high-temperature oxidation, and the reduced fatigue life was attributed
to oxidation-fatigue interaction. Fatigue life was maximum at the intermediate strain rates, where strain localization was
lower. Strain localization as a function of strain rate and temperature was quantified by optical and scanning electron microscopy
and correlated with fatigue life. 相似文献
15.
Y. T. Peng P. B. Aswath A. R. Koymen 《Metallurgical and Materials Transactions A》1994,25(5):1041-1050
The surface of a Ti-48 at. Pct Al alloy was examined by Auger electron microscopy to study oxidation at room temperature.
On exposure to air at room temperature, both Al and Ti oxides were observed together with an abundance of C. The amount of
C was always larger in the two-phase α2
+ γ region compared to the single-phase γ region. The Ti oxides formed on the surface of they grains were primarily Ti2O3 rather than TiO2. On depth profiling with Ar+ ion sputtering, lower oxide states of Ti were found. This was attributed to either the Ar+ ion sputtering or the fact that the inner layers of oxide represented oxides of Ti in their lower valence states. The A12O3 was stable and did not exhibit any transient oxidation states. The dominant oxidation product on the surface of sputtered
single-phase γ grains after an 84-hour exposure in the ultrahigh vacuum Auger chamber at room temperature is A12O3. A depletion of C and O occurred beneath the oxide surface in some γ grains. The chemical shift between the Al L2,3MM and A12O3 L2,3(A1)M(O)M(O) peaks in the Auger spectrum of A12O3 formed on the γ phase in TiAl was found to be 11 eV.
Y.T. Peng, Graduate Student, Formerly with the Materials Science and Engineering Program, University of Texas at Arlington,
Arlington, TX 76019, 相似文献
16.
The microstructural evolution of a (Ni,Pt)-aluminide bond coat underneath the ZrO2-based thermal-barrier coating (TBC) topcoat system on a René N5 Ni-based superalloy turbine blade during prolonged high-temperature
service has been characterized using transmission electron microscopy (TEM). The as-deposited bond coat has a spatially varying
microstructure, which consists of an outer layer of single-phase β-(Ni,Pt)Al, a middle layer of a β-(Ni,Pt)Al matrix containing a high number density of μ-phase precipitates, and an inner layer containing a γ/γ′ matrix and numerous μ- and σ-phase precipitates. During service, microstructural changes in the hotter sections of the blade are more extensive than those
in the cooler parts, as expected. As a result of interdiffusion, the inner layer grows into the γ/γ′ substrate, with the formation of some M23C6 precipitates, and the β matrix in the middle layer is transformed into a two-phase mixture of β and γ′. Corresponding changes occur in the morphologies and volume fractions of the various precipitate phases present in the bond
coat. The single-phase β material in the outer layer retains its basic structure, except that the compositional changes due to diffusion between the
bond coat and turbine blade cause a martensitic transformation to occur in the hottest sections during the final cooling of
the blade. The distribution of various elements in the different layers has also been analyzed, as has growth of the thermally
grown oxide (TGO) at the bond coat/TBC interface. 相似文献
17.
The Ostwald ripening of Al3Sc precipitates in an Al-0.28 wt pct Sc alloy during aging at 673, 698, and 723 K has been examined by measuring the average
size of precipitates by transmission electron microscopy (TEM) and the reduction in Sc concentration in the Al matrix with
aging time, t, by electrical resistivity. The coarsening kinetics of Al3Sc precipitates obey the t
1/3 time law, as predicted by the Lifshitz-Slyozov-Wagner (LSW) theory. The kinetics of the reduction of Sc concentration with
t are consistent with the predicted t
−1/3 time law. Application of the LSW theory has enabled independent calculation of the Al/Al3Sc interface energy, γ, and volume diffusion coefficient, D, of Sc in Al during coarsening of precipitates. The Gibbs-Thompson equation has been used to give a value of γ using coarsening data obtained from TEM and electrical resistivity measurements. The value of γ estimated from the LSW theory is 218 mJ m−2, which is nearly identical to 230 mJ m−2 from the Gibbs-Thompson equation. The pre-exponential factor and activation energy for diffusion of Sc in Al are determined
to be (7.2±6.0)×10−4 m2 s−1 and 176±9 kJ mol−1, respectively. The values are in agreement with those for diffusion of Sc in Al obtained from tracer diffusion measurements. 相似文献
18.
S. N. S. Reddy L. B. Wiggins D. N. Leonard K. T. Jacob 《Metallurgical and Materials Transactions A》2005,36(10):2685-2694
As a model of an internal displacement reaction involving a ternary oxide “line” compound, the following reaction was studied
at 1273 K as a function of time, t:
Both polycrystalline and single-crystal materials were used as the starting NiTiO3 oxide. During the reaction, the Ni in the oxide compound is displaced by Fe and it precipitates as a γ-(Ni-Fe) alloy. The reaction preserves the starting ilmenite structure. The product oxide has a constant Ti concentration
across the reaction zone, with variation in the concentration of Fe and Ni, consistent with ilmenite composition. In the case
of single-crystal NiTiO3 as the starting oxide, the γ alloy has a “layered” structure and the layer separation is suggestive of Liesegang-type precipitation. In the case of polycrystalline
NiTiO3 as the starting oxide, the alloy precipitates mainly along grain boundaries, with some particles inside the grains. A concentration
gradient exists in the alloy across the reaction zone and the composition is >95 at. pct Ni at the reaction front. The parabolic
rate constant for the reaction is k
p
=1.3 × 10−12 m2 s−1 and is nearly the same for both single-crystal and polycrystalline oxides. 相似文献
19.
Amit Siddharth Sharma Krishanu Biswas Bikramjit Basu 《Metallurgical and Materials Transactions A》2014,45(1):482-500
The dispersion of a softer phase in a metallic matrix reduces the coefficient of friction (COF), often at the expense of an increased wear rate at the tribological contact. To address this issue, unlubricated fretting wear tests were performed on spark plasma sintered Cu-Pb nanocomposites against bearing steel. The sintering temperature and the Pb content as well as the fretting parameters were judiciously selected and varied to investigate the role of microstructure (grain size, second-phase content) on the wear resistance properties of Cu-Pb nanocomposites. A combination of the lowest wear rate (~1.5 × 10?6 mm3/Nm) and a modest COF (~0.4) was achieved for Cu-15 wt pct Pb nanocomposites. The lower wear rate of Cu-Pb nanocomposites with respect to unreinforced Cu is attributed to high hardness (~2 to 3.5 GPa) of the matrix, Cu2O/Fe2O3-rich oxide layer formation at tribological interface, and exuding of softer Pb particles. The wear properties are discussed in reference to the characteristics of transfer layer on worn surface as well as subsurface damage probed using focused ion beam microscopy. Interestingly, the flash temperature has been found to have insignificant effect on the observed oxidative wear, and alternative mechanisms are proposed. Importantly, the wear resistance properties of the nanocomposites reveal a weak Hall–Petch-like relationship with grain size of nanocrystalline Cu. 相似文献
20.
S. Das A. T. Morales A. R. Riahi X. Meng-Burany A. T. Alpas 《Metallurgical and Materials Transactions A》2011,42(8):2384-2401
Friction maps have been developed to explain the behavior of aluminum alloys under dynamic tribological conditions generated
by the simultaneous effects of temperature and strain rate. A specially designed tribometer was used to measure the coefficient
of friction (COF) of AA5083 strips subjected to sliding with a simultaneous application of tensile strain in the temperature
range of 693 K to 818 K (420 °C to 545 °C) and strain rates between 5 × 10−3 s−1 and 4 × 10−2 s−1. The mechanisms of plastic deformation, namely, diffusional flow, grain boundary sliding (GBS), and solute drag (SD), and
their operation ranges were identified. Relationships between the bulk deformation mechanism and COF were represented in a
unified map by superimposing the regions of dominant deformation mechanisms on the COF map. The change in COF (from 1.0 at
693 K (420 °C) and 1 × 10−2 s−1 to 2.1 at 818 K (545 °C) and 4 × 10−2 s−1) was found to be largest in the temperature–strain rate region, where GBS was the dominant deformation mechanism, as a result
of increased surface roughness. The role of bulk deformation mechanisms on the evolution of the surface oxide layer damage
was also examined. 相似文献