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1.
Theflowstressofamaterialrelatesnotonlytothestrain ,strainrate ,andtemperatureofde formation,butalsotothemicrostructure .Asanessentialinputforcomputermodelingthermome chanicalprocessingoperationsusingfiniteelementmethods,anaccurateflowstressvalueorflowstre… 相似文献
2.
The characteristics of hot deformation of an α+β titanium alloy Ti-6.5Al-3.5Mo-1.5Zr-0.3Si with acicular microstructure were studied using isothermal hot compressive tests in a strain rate range of 0.01-10 s-1 at 860-1 100 °C. The true stress-true strain curves of alloy hot-compressed in the α+β region exhibit a peak stress followed by continuous flow softening; whereas in the β region,the flow stress attains a steady-state regime. At a strain rate of 10 s-1 and in a wide temperature range,the alloy exhibit... 相似文献
3.
High temperature plastic deformation behavior of non-orientated electrical steel was investigated by Gleeble 1500 thermo-mechanical
simulator at strain rate of 0.01−10 s−1 and high temperature of 500–1 200 °C. The stress level factor (a), stress exponent (n), structural factor (A) and activation energy (Q) of high temperature plastic deformation process of non-orientated electrical steel in different temperature ranges were
calculated by the Arrhenius model. The results show that, with dynamic elevation of deformation temperature, phase transformation
from α-Fe to γ-Fe takes place simultaneously during plastic deformation, dynamic recovery and dynamic recrystallization process, leading
to an irregular change of the steady flow stress. For high temperature plastic deformation between 500 and 800°C, the calculated
values of a, n, A, and Q are 0.039 0 MPa−1, 7.93, 1.9×1018 s−1, and 334.8 kJ/mol, respectively, and for high temperature plastic deformation between 1 050 and 1 200 °C, the calculated
values of a, n, A, and Q are 0.125 8 MPa−1, 5.29, 1.0×1028 s−1, and 769.9 kJ/mol, respectively.
Foundation item: Project(2005038560) supported by the Postdoctoral Foundation of China; Project(05GK1002-2) supported by Key Program of Hunan
Province 相似文献
4.
Constitutivemodelisamathematicalrepresentationofthedeformationresponseofamaterialtoexternallyap pliedloading ,includingenvironmentalfactors .Thepre ciseknowledgeoftheconstitutivebehaviorofthematerialisthefoundationofnumericalsimulationtechnologyofmateri… 相似文献
5.
Isothermal compression tests at temperatures from 1 273 to 1 423 K and strain rates from 0.1 to 10 s-1 were carried out to investigate the flow behaviors of Q420qE steel.Stress-strain data collected from the tests were employed to establish the constitutive equation,in which the influence of strain was incorporated by considering the effect of strain on material constants Q,n,α,and ln A.The results show that the flow stress curves are dependent on the strain,strain rate and deformation temperature.They disp... 相似文献
6.
1 INTRODUCTIONDuringhotworking ,severalmetallurgicalphenomenasuchaswork hardening (WH ) ,dynamicrecovery (DRV) ,anddynamicre crystallizaiton (DRX )occursimultaneous ly[1 5 ] .Especially ,theoccurrenceofDRX ,canrefinegrainandreducedeformationresistanceinpracticalhot w… 相似文献
7.
刘勇 《武汉理工大学学报(材料科学英文版)》2009,24(2):202-205
Hot compressive behaviors of Ti-6Al-2Zr-1Mo-1V alloy at 800 °C, as well as the evolution of microstructure during deformation
process, were investigated. The experimental results show that flow stress increases to a peak stress followed by a decease
with increasing strain, and finally forms a stable stage. Dislocations are generated at the interface of α/β phase, and the phase interface and dislocation loops play an important role in impeding the movement of dislocation. As strain
increasing, micro-deformation bands with high-density dislocation are formed, and dynamic recrystallizaton occurs finally.
XRD Fourier analysis reveals that dislocation density increases followed by a decrease during compressive deformation, and
falls into the range from 1010 to 1011 cm−2. 相似文献
8.
LIU Jie FAN GuangWei HAN PeiDe LIU JianSheng GE DongSheng & QIAO GuanJun School of Materials Science Engineering Xi’an Jiaotong University Xi’an China College of Materials Science Engineering Taiyuan University of Science Technology Taiyuan Taiyuan Iron Steel Company Ltd. Taiyuan College of Materials Science Engineering Taiyuan University of Technology 《中国科学E辑(英文版)》2009,52(8):2167-2171
Gleeble-1500D thermal simulation tester was employed in the hot-compression investigation of as-cast nuclear 304 austenitic stainless steel under conditions: deformation temperature 950―1200℃; deformations 30% and 50%; deformation rates 0.01 and 0.1 s?1. The results show that the flow stress decreases with temperature rise under the same strain rate and deformation, that the flow stress increases with deformation under the same temperature and strain rate, and that the flow stress increases with strain rate... 相似文献
9.
In order to establish a model between the grain size and the process parameters, the hot deformation behaviors of Ti-49.5Al alloy was investigated by isothermal compressive tests at temperatures ranging from 800 to 1 100 ℃ with strain rates of 10^-3-10^-1 s^-1. Within this range, the deformation behavior obeys the power law relationship, which can be described using the kinetic rate equation. The stress exponent, n, has a value of about 5.0, and the apparent activation energy is about 320 J/mol, which fits well with the value estimated in previous investigations. The results show that, the dependence of flow stress on the recrystallized grain size can be expressed by the equation: σ = K1 drex^-0.56. The relationship between the deformed microstructure and the process control parameter can be expressed by the formula: lgdrex= -0.281 1gZ 3.908 1. 相似文献
10.
1IntroductionAs a typical wrought magnesiumalloy,AZ31alloyhas a wide prospect for applications inthe fields of auto-mobiles,electronic appliances and aeronautic facili-ties[1,2].However,due to the hexagonal close-packed(HCP)structure of magnesium,the ductility of AZ31al-loy at roomtemperature is rather poor,which greatly re-stricts its applications in structural fields[3-5].Owing tothe activation of non-basal slip system[6],the ductility ofMg alloycan be significantlyimproved at elevatedtem… 相似文献
11.
Based on the steady-state strain measured by single-pass hot compression tests, the method by a double-pass hot compression
testing was developed to measure the metadynamic-recrystallization kinetics. The metadynamic recrystallization behavior of
low-alloy steel Q345B during hot compression deformation was investigated in the temperature range of 1 000–1 100 °C, the
strain rate range of 0.01–0.10 s−1 and the interpass time range of 0.5–50 s on a Gleeble-3500 thermo-simulation machine. The results show that metadynamic recrystallization
during the interpass time can be observed. As the deformation temperature and strain rate increase, softening caused by metadynamic
recrystallization is obvious. According to the data of thermo-simulation, the metadynamic recrystallization activation energy
is obtained to be Q
md=100.674 kJ/mol and metadynamic recrystallization kinetics model is set up. Finally, the error analysis of metadynamic recrystallization
kinetics model proves that the model has high accuracy (correlation coefficient R=0.988 6). 相似文献
12.
马立强 《武汉理工大学学报(材料科学英文版)》2008,23(4):551-557
The dynamic recrystallization (DRX) behavior of Nb-Ti microalloyed steels was investigated by isothermal single compression tests in the temperature range of 900-1 150 ℃ at constant strain rates of 0.1-5 s^-1. DRX was retarded effectively at low temperature due to the onset of dynamic precipitation of Nb and Ti carbonitrides, resulting in higher values of the peak strain. An expression was developed for the activation energy of deformation as a function of the contents of Nb and Ti in solution as well as other alloying elements. A new value of corrective factor was determined and applied to quantify the retardation produced by increase in the amount of Nb and Ti dissolved at the reheating temperature. The ratio of critical strain to peak strain decreases with increasing equivalent Nb content. In addition, the effects of Ti content and deformation conditions on DRX kinetics and steady state grain size were determined. Finally, the kinetics of dynamic precipitation was determined and effect of dynamic precipitation on the onset of DRX was clarified based on the comparison between precipitate pinning force and recrystallization driving force. 相似文献
13.
Vacuummembranedistillation(VMD)isapromisingseparationtechniqueforthepurificationofdiluteaqueoussolutions,suchasseparationofgasesfromaqueoussolu tionsandremovalofvolatileorganiccomponents(VOC)fromdiluteaqueoussolutions .Inrecentyears ,theremo valofVOCfromd… 相似文献
14.
A heterotrophic acidothermophilic bacterial strain, YNTC-1, was isolated from an acidic hot spring in Tengchong, Yunan, China. YNTC-1 grows at pH value of 1.5-8.0 and temperature of 40-70 ℃, with optimal pH and temperature at 3.0 and 55 ℃, respectively. The cells of the strain are in shape of short rod, with 1.0-1.2 μm in length and 0.7-0.8 μm in diameter, and with distinct spores at both poles of each cell. The predominant fatty acids in cellular membrane of the strain are C18:1 ω7c. 16s rRNA gene analysis reveals that this strain is closely related to Alicyclobacillus sendaiensis, with over 99% sequence similarity. Based on phenotypic and genotypic analyses, YNTC-1 is identified as a member ofA. sendaiensis. Considering some important morphological and biochemical differences between strain YNTC-1 and A. sendaiensis ATCC 27009T, YNTC-1 may be proposed to be a novel subspecies of A. sendaiensis. However, this viewpoint has to be confirmed by further studies. Co-bioleaching of pyrite and chalcopyrite with strain YN22, Sulfobacillus thermosulfidooxidans, shows that strain YNTC-1 has no evident influence on bioleaching rates of these two sulphide minerals. 相似文献
15.
The strain Lv(1- z) isolated from the Henan bauxite was characterized by morphological observation, biochemical and physiological identification, and 16S rDNA sequence analysis. The influences of temperature, initial pH value, the volume of medium, shaking speed and illite concentration on the desilicating ability of the strain Lv(1- z) were investigated. The results show that the bacterium is a Gram-negative rod-shaped bacterium with oval endspores and thick capsule, but without flagellum. The biochemical and physiological tests indicate that the strain Lv(1- z) is similar to Bacillus rnucilaginosus. In GenBank the 16S rDNA sequence similarity of the strain Lv(1- z) and the B. rnucilaginosus YNUCC0001(AY571332) is more than 99%. Based on the above results, the strain Lv(1- z) is identified as B. rnucilaginosus. The optimum conditions for the strain L(1- z) to remove silicon from illite are as follows., temperature is 30℃ ;initial pH value is 7.5; medium volume in 200 mL bottle is 60 mL; shaking speed of rotary shaker is 220 r/m ; illite concentration is 1%. 相似文献
16.
The flow stress behavior of SCM435 steel was studied by using a MMS-200 thermal simulation machine, under the conditions with deformation temperatures of 1023–1323 K and strain rate of 0.01–10 s?1. The experimental results indicated that the critical strain would get smaller with the increment in temperature and the decrement in strain rate, leaving the dynamic recrystallization easier to occur. The peak stress constitutive equation of SCM435 steel under high temperatures was established by the form of hyperbolic sine, and the activation energy of deformation under high temperature was obtained by regression equation. The critical strain ? c for dynamic recrystallization was accurately derived from the θ-σ curve containing strain hardening rate θ and flow stress σ. Then the correlation between peak stress, peak strain, critical stress, critical strain and the parameter Z was further obtained. The Avrami kinetic equation of dynamic recrystallization for SCM435 steel was developed from stress-strain curve, and the Avrami exponent m was abstracted. Observations also indicated that the Avrami constants would decrease with increments in temperature, but increase with increments in strain rate. The Avrami constant took small influence from the deforming temperature, but significant influence from strain rate, and the correlation between Avrami constant and the strain rate was obtained by regression equation. 相似文献
17.
Creep properties and permeability evolution in triaxial rheological tests of hard rock in dam foundation 总被引:2,自引:0,他引:2
Triaxial creep tests were carried out under seepage pressure by using rock servo-controlled triaxial rheology testing equipment.
Based on experimental results, rock rheological properties influenced by seepage-stress coupling were studied, and variations
of seepage rate with time in complete creep processes of rock were analyzed. It is shown that, when the applied stress is
less than failure stress level, the creep deformation is not obvious, and its main form is steady-state creep. When applied
stress level is greater than or less than but close to fracture stress, it is easier to see the increase of creep deformation
and the more obvious accelerative creep characteristics. The circumferential creep deformation is obviously higher than the
axial creep deformation. At the stage of steady-state creep, the average of seepage flow rate is about 4.7×10−9 m/s at confining pressure (σ
3) of 2 MPa, and is about 3.9×10−9 m/s at σ
3 of 6 MPa. It is seen that the seepage flow rate at σ
3 of 2 MPa in this case is obviously larger than that at σ
3 of 6 MPa. At the stage of creep acceleration, the seepage flow rate is markedly increased with the increase of time. The
variation of rock permeability is directly connected to the growth and evolution of creep crack. It is suggested that the
permeability coefficient in complete creep processes of rock is not a constant, but is a function of rock creep strain, confining
pressure, damage variable and pore water pressure. The results can be considered to provide a reliable reference for the establishment
of rock rheological model and parameter identification. 相似文献
18.
The effect of strain hardening and strain softening behavior of flow stress changing with temperature on welding residual stress,plastic strain and welding distortion of A7N01-T4 aluminum alloy was studied by finite simulation method.The simulation results show that the weld seam undergoes strain hardening in the temperature range of 180-250 ℃,however,it exhibits strain softening at temperature above 250 ℃ during welding heating and cooling process.As a result,the strain hardening and strain softening effec... 相似文献
19.
In order to establish the quantitative relationship between equivalent strain and the performance index of the deformed material
within the range of certain passes for equal channel angular processing (ECAP), a new approach to characterize the equivalent
strain was proposed. The results show that there exists better accordance between mechanical property (such as hardness or
strength) and equivalent strain after rolling and ECAP in a certain range of deformation amount, and Gauss equation can be
satisfied among the equivalent strain and the mechanical properties for ECAP. Through regression analysis on the data of hardness
and strength after the deformation, a more generalized expression of equivalent strain for ECAP is proposed as: ɛ=k
0exp[−(k
1
M−k
2)2], where M is the strength or hardness of the material, k
1 is the modified coefficient (k
1∈(0, 1)), k
0 and k
2 are two parameters dependent on the critical strain and mechanical property that reaches saturation state for the material,
respectively. In this expression the equivalent strain for ECAP is characterized novelly through the mechanical parameter
relating to material property rather than the classical geometry equation.
Foundation item: Projects(50471102, 50671089) supported by the National Natural Science Foundation of China 相似文献
20.
Compressive mechanical properties of 10# low carbon steel with normalizing heat treatment are studied.A Gleeble system is adopted to analyze the quasi-static properties and thermal softening effects of heat treated 10# steel,while a Hopkinson bar apparatus is used to investigate its dynamic characteristics under different strain rates.The results show that yield stress of heat treated 10# steel is more than that of untreated one at room temperature.When the specimens are tested at different temperatures,yield stresses decrease with increasing temperature except 573 K.Moreover,the influence of strain rate on yield stress are verified,which shows that the yield stress increases sharply from 500 s-1 to 1 890 s-1,while it changes a little from 1 890 s-1 to 4 850 s-1.The results indicate that yield stress is mainly influenced by hardening effect at low strain rate and controlled by both thermal softening effect and strain rate hardening effect at high strain rate. 相似文献