共查询到20条相似文献,搜索用时 15 毫秒
1.
L. L. Rokhlin S. V. Dobatkin T. V. Dobatkina N. I. Nikitina I. E. Tarytina E. V. Tat’yanin M. V. Popov 《Russian Metallurgy (Metally)》2006,(1):80-85
The effect of severe plastic deformation by high-pressure torsion on the structure and properties of aged magnesium alloys containing 2.8–5.5 wt % Sm (the maximum solubility of samarium in solid magnesium is 5.8 wt %) are studied. The severe plastic deformation leads to substantial strengthening caused by the formation of a submicrocrystalline structure along with strengthening caused by the decomposition of a supersaturated magnesium-based solid solution. 相似文献
2.
V. M. Segal 《Russian Metallurgy (Metally)》2006,(5):474-483
The mechanics of severe plastic deformation (SPD) is considered. Unlike steady-state plastic flows with the continuous evolution of dislocation structures, the SPD-induced microlocalization strongly depends on the deformation mode. The quantitative characteristic of a deformation mode is determined by the distribution of strain rates over the principal directions of a continuum shear and corresponds to the limiting states of pure shear and simple shear. Simple models of SPD mesomechanics demonstrate that a deformation mode affects a transition to localization, localization in shear bands, and rotational localization. The simple shear mode is shown to correspond to the optimum scheme of plastic structure formation, including the development of high-angle boundaries and grain refinement. Various SPD processes are analyzed in terms of simple shear. 相似文献
3.
The evolution of the microstructure and the properties of an austenitic high-manganese steel subjected to severe deformation by cold rolling and subsequent recrystallization annealing is investigated. Cold rolling is accompanied by mechanical structural twinning and shear banding. The microhardness and microstructural analysis of annealed samples are used to study the recrystallization kinetics of the high-manganese steel. It is shown that large plastic deformation and subsequent annealing result in rapid development of recrystallization processes and the formation of an ultrafine-grained structure. A completely recrystallized structure with an average grain size of 0.64 μm forms after 30-min annealing at a temperature of 550°C. No significant structural changes are observed when the annealing time increases to 18 h, which indicates stability of the recrystallized microstructure. The steel cold rolled to 90% and annealed at 550°C for 30 min demonstrates very high strength properties: the yield strength and the tensile strength achieve 650 and 850MPa, respectively. The dependence of the strength properties of the steel on the grain size formed after rolling and recrystallization annealing is described by the Hall–Petch relation. 相似文献
4.
S. V. Dobatkin L. L. Rokhlin T. V. Dobatkina N. I. Nikitina I. E. Tarytina 《Russian Metallurgy (Metally)》2011,(7):629-633
The effect of severe plastic deformation and subsequent aging on the structure and properties of cast and hardened magnesium alloys containing samarium and yttrium is studied. Severe plastic deformation leads to additional hardening both before and after aging. Hardening is achieved by the formation of nanocrystalline structure in quenched alloys or submicrocrystalline structure in cast alloys. Severe plastic deformation results in the rapid decomposition of a supersaturated magnesium solid solution and additional hardening due to the formation of nano-sized particles of hardening phases. 相似文献
5.
I. P. Semenova 《Russian Metallurgy (Metally)》2010,(9):831-836
The formation of an ultrafine-grained structure (UFGS) in titanium by severe plastic deformation significantly increases its mechanical properties, among them fatigue strength. In this work, high mechanical properties of titanium long rods are achieved using a combination of equal-channel angular pressing and subsequent thermal and thermomechanical treatment. The formation of a homogeneous UFGS in a rod of commercial titanium is found to increase the fatigue limit by a factor of about 1.5. Moreover, the fatigue strength of UFGS titanium estimated on notched specimens is higher than that of coarse-grained titanium, which is important for its structural application in medicine. 相似文献
6.
D. Raabe 《Metallurgical and Materials Transactions A》1995,26(4):991-998
The microstructure and texture of a strip-cast as well as a hot-rolled austenitic stainless steel (18 pct Cr, 8.5 pct Ni)
are investigated by the use of optical metallography and quantitative X-ray texture analysis. In the hot band, a homogeneous
microstructure is revealed together with a through-thickness texture gradient consisting of a weak cold rolling type of texture
in the center layer and a shear texture close to the surface layers. The result is discussed in terms of the through-thickness
shear profile that is generated during hot rolling. In the strip-cast material, a random orientation distribution as well
as the development of martensite close to the center layer is attributed to the impingement and deformation of the films that
are solidified on the surfaces of the casting rolls. The texture close to the surface is attributed to the growth selection
of {001}〈uvw〉 oriented grains. 相似文献
7.
The structure and properties of β III titanium alloy (nominal composition: 11.5 pct Mo, 6 pct Zr, 4.5 pct Sn, bal Ti) were
studied as a function of combined high and low temperature ther-momechanical processing. A water quenched extrusion was deformed
various amounts by swaging at room temperature prior to the aging treatment. No re-solution heat treatment was employed. The
swaging introduced mechanical twinning and a small amount of stress induced orthorhombic martensite. Following a 900°F, 8
hr aging treatment, substantial increases in yield and tensile strength were observed, combined with a severe decrease in
tensile ductility in samples with small amounts of swaging. The orientation and morphology of the deformation products have
a critical influence on tensile ductility. A decrease in the plane strain fracture toughness accompanied the large increase
in tensile strength. 相似文献
8.
M. G. Isaenkova Yu. A. Perlovich V. A. Fesenko T. I. Dement’eva V. Yu. Gol’tsev 《Russian Metallurgy (Metally)》2013,2013(4):300-303
The texture formation in the single crystals of the Ti-48 at % Ni-2 at % Fe alloy rolled at a temperature of 350°C up to a strain of 80% in eleven different initial orientations is examined. There are three stable initial orientations that remain unchanged in rolling: {011}〈011〉, {111}〈011〉, and {111}〈112〉. The TiNi single crystals are shown to be deformed by means of a combined action of slip in systems {011}〈001〉 and twinning in systems {114}〈221〉 and {118}〈441〉. The types of formed rolling texture in the single crystals depend on their initial orientation and strain. 相似文献
9.
Depth-sensing indentation is used to study the effect of grain refinement to submicro- and nanograins on the mechanical properties (hardness, plasticity, Young’s modulus) of armco iron subjected to severe plastic deformation by attrition in argon. In contrast to fcc metals, where the hardness increases and the plasticity decreases as the grain size decreases to 20 nm, the hardness of bcc iron decreases from 5.8 to 3.7 GPa and plasticity δ A increases from 0.82 to 0.87 as the grain size decreases from 50 to 20 nm. 相似文献
10.
D. W. Brown S. P. Abeln W. R. Blumenthal M. A. M. Bourke M. C. Mataya C. N. Tomé 《Metallurgical and Materials Transactions A》2005,36(4):929-939
Weakly textured hot-pressed (HP) beryllium and strongly textured hot-rolled beryllium were compressed using a split-Hopkinson
pressure bar (SHPB) (strain rate ∼4500 s−1) to a maximum of 20 pct plastic strain as a function of temperature. The evolution of the crystallographic texture was monitored
with neutron diffraction and compared to polycrystal plasticity models for the purpose of interpretation. The macroscopic
response of the material and the active deformation mechanisms were found to be highly dependent on the orientation of the
load with respect to the initial texture. Specifically, twinning is inactive when loaded parallel to the strong basal fiber
but accounts for 27 pct of the plastic strain when loaded transverse to the basal fiber. In randomly textured samples, 15
pct of the plastic strain is accomplished by twinning. The role of deformation mechanisms with components out of the basal
plane (i.e., twinning and pyramidal slip) is discussed. 相似文献
11.
A. E. Kravchik G. A. Savel'ev V. S. Neshpor S. S. Ordan'yan 《Powder Metallurgy and Metal Ceramics》1977,16(3):163-166
Conclusions A study of the fine-structure parameters of niobium carbide powders has shown that nonstoichiometric carbides are more brittle than stoichiometric niobium carbide. This is due, firstly, to the formation of vacancy complexes in carbon-deficient sublattices and to the generation of Frank dislocations, which markedly hinder the motion of existing and nucleation of new dislocations, and, secondly, to the increase in Peierls-Nabarro forces brought about by a fall in the carbon content of niobium carbide.Translated from Poroshkovaya Metallurgiya, No. 3(171), pp. 7–11, March, 1977. 相似文献
12.
S. V. Zherebtsov 《Russian Metallurgy (Metally)》2012,2012(11):969-974
The efficiency of strengthening induced by microstructure refinement to an ultrafine-grained (UFG) state is studied on commercial purity VT1-0 titanium and two-phase VT6 and VT22 titanium alloys. An UFG structure with a grain size <0.5 μm is formed by multiaxial isothermal deformation. The refinement of a titanium microstructure to a grain size of ~0.4 μm is found to result in an almost twofold increase in the strength and the fatigue limit. The strength of a VT22 alloy with an UFG structure is equal to that of the thermally strengthened alloy. The strength and fatigue limit of a VT6 alloy with an UFG structure are higher than those of the thermally strengthened state by approximately 25%. The strengthening by microstructure refinement is found to be expedient for low and medium alloys. 相似文献
13.
The purpose of this article is to provide a comprehensive and coordinated review of the evolution of texture during thermomechanical processing of titanium and its alloys. In general, the evolution of texture depends on several factors such as deformation temperature, mode of deformation (rolling, forging and extrusion), initial texture and microstructure, degree and rate of deformation and alloying elements. Phase transformation textures and associated variant selection mechanisms as function of initial texture and heat treatment have also been discussed. The chronological developments of texture modelling and deformation mechanisms in these alloys are presented. 相似文献
14.
Depth-sensing indentation is used to study the effect of grain refinement to submicro- and nanograins on the mechanical properties (hardness, plasticity, Young’s modulus) of armco iron subjected to severe plastic deformation by attrition in argon. In contrast to fcc metals, where the hardness increases and the plasticity decreases as the grain size decreases to 20 nm, the hardness of bcc iron decreases from 5.8 to 3.7 GPa and plasticity δ A increases from 0.82 to 0.87 as the grain size decreases from 50 to 20 nm. 相似文献
15.
Localization of plastic deformation and evolution of block structure in submicrocrystalline titanium
B. S. Semukhin V. I. Danilov N. A. Ploskov G. V. Shlyakhova 《Steel in Translation》2013,43(10):644-646
The plastic deformation of submicrocrystalline titanium is considered. By speckle photography and X-ray diffraction analysis, the distribution of local deformation and elastic stress in the working section of the samples is studied. At the prefailure stage, a site of localized deformation is formed, with maximum components of the distortion tensor. The elastic distortion reaches a maximum at the boundaries of this site and then declines. The size of the crystallites is reduced at the site of localized deformation. 相似文献
16.
Bing Q. Han Farghalli A. Mohamed Enrique J. Lavernia 《Metallurgical and Materials Transactions A》2003,34(1):71-83
In the present study, the mechanical properties of Fe processed via severe plastic deformation (equal-channel angular pressing (ECAP)) at room temperature were investigated for the first time.
The grain size of annealed Fe, with an initial grain size of about 200 μm, was reduced drastically during ECAP. After eight passes, the grain size reaches 200 to 400 nm, as documented by means of
transmission electron microscopy (TEM). The value of microhardness during pressing increases 3 times over that of the starting
material after the first pass and increases slightly during subsequent pressing for higher-purity Fe. Examination of the value
of microhardness after eight passes as a function of post-ECAP annealing temperature shows a transition from recovery to recrystallization,
an observation that resembles the behavior reported for heavily deformed metals and alloys. The tensile and compression behaviors
were examined. In tension, a drop in the engineering stress-engineering strain curve beyond maximum load was observed both
in the annealed Fe and the ECAP Fe. This drop is related to the neck deformation. The fracture surface, examined by scanning
electron microscopy (SEM), shows vein patterns, which is different from the dimples found on the fracture surface of annealed
Fe. In compression, an initial strain-hardening region followed by a no-strain-hardening region was observed in the ECAP Fe.
The yield strength in tension of the ECAP Fe was observed to be higher than that in compression. The strengthening mechanisms
and softening behavior are discussed. 相似文献
17.
S. V. Dobatkin V. V. Zakharov A. Yu. Vinogradov K. Kitagawa N. A. Krasil’nikov T. D. Rostova E. N. Bastarash 《Russian Metallurgy (Metally)》2006,(6):533-540
The possibility of formation of a nanocrystalline structure (with a grain size smaller than 100 nm) in four Al-Mg-Sc alloys with 3.1–5.9% Mg during severe plastic deformation by torsion at a hydrostatic pressure of 6 GPa (high-pressure torsion (HPT)) has been studied. Room-temperature HPT of the alloys is shown to produce a nanocrystalline structure if the magnesium content is more than 4% (in the range 0.16–0.31% Sc). As the magnesium content increases, the grain size decreases and is minimal (40–50 nm) in a 01570 alloy with 5.9% Mg and 0.3% Sc. The structure of the HPT-processed 01570 alloy remains nanocrystalline upon heating to 200°C or at a deformation temperature as high as 200°C. Postdeformation heating is found to cause aging processes. The hardening of all the Al-Mg-Sc alloys is maximal after HPT at 20°C followed by aging at 300°C. 相似文献
18.
19.
Dong-Woo Suh Chang-Seok Oh Sung-Joon Kim 《Metallurgical and Materials Transactions A》2005,36(4):1057-1059
High-angle grain-boundary spacing in deformed austenite is analyzed using Ni-30Fe alloy to explain the change of ferrite grain
size by severe plastic deformation (SPD) of austenite in low carbon steel. It is suggested that constant high-angle grain-boundary
spacing in deformed austenite resulting from dynamic recrystallization (DRX) or geometric DRX is responsible for the limit
of ferrite grain refinement over a certain level of plastic deformation of austenite. 相似文献
20.
《Acta Metallurgica Materialia》1993,41(9):2611-2624
We present in this work a visco-plastic self-consistent (VPSC) anisotropic approach for modeling the plastic deformation of polycrystals, together with a thorough discussion of the assumptions involved and the range of application of such approach. We use the VPSC model for predicting texture development during rolling and axisymmetric deformation of Zirconium alloys, and to calculate the yield locus and the Lankford coefficient of rolled Zircaloy sheet. We compare our results with experimental data and find that they are in good agreement with the available experimental evidence. We also compare the VPSC predictions with the ones of a Full Constraints approach and observe that they differ both quantitatively and qualitatively: according with the predictions of the VPSC scheme, deformation is accommodated mostly by the soft systems, the twinning activity is much lower, and fewer systems are active, in average, per grain. These results are a consequence of having accounted for the grain interaction with its surroundings, which is a crucial aspect when modeling plastically anisotropic materials. 相似文献