Effect of deformation temperature on the hot compressive behavior of metal matrix composites with misaligned whiskers

A multi-inclusion cell model is used to investigate the effect of deformation temperature and whisker rotation on the hot compressive behavior of metal matrix composites with misaligned whiskers. Numerical results show that deformation temperature influences the work-hardening behavior of the matrix and the rotation behavior of the whiskers. With increasing temperature, the work hardening rate of the matrix decreases, but the whisker rotation angle increases. Both whisker rotation and the increase of deformation temperature can induce reductions in the load supported by whisker and the load transferred from matrix to whisker. Additionally, it is found that during large strain deformation at higher temperatures, the enhancing of deformation temperature can reduce the effect of whisker rotation. Meanwhile, the stress-strain behavior of the composite is rather sensitive to deformation temperature. At a relatively lower temperature （150℃）, the composite exhibits work hardening due to the matrix work hardening, but at relatively higher temperatures （300℃ and above）, the composite shows strain softening due to whisker rotation. It is also found that during hot compression at higher temperatures, the softening rate of the composite decreases with increasing temperature. The predicted stress-strain behavior of the composite is approximately in agreement with the experimental results.

High temperature deformation and recrystallization behavior of magnesium bicrystals with 90°<1010>and 90°<1120>tilt grain boundaries

The deformation mechanisms and dynamic recrystallization(DRX)behavior of specifically grown bicrystals with a symmetric 90°<1010>and 90°<1120>tilt grain boundary,respectively,were investigated under deformation in plane strain compression at 200℃and 400℃.The microstructures were analyzed by panoramic optical microscopy and large-area electron backscatter diffraction(EBSD)orientation mapping.The analysis employed a meticulous approach utilizing hundreds of individual,small EBSD maps with a small step size that were stitched together to provide comprehensive access to orientation and misorientation data on a macroscopic scale.Basal slip primarily governed the early stages of deformation at the two temperatures,and the resulting shear induced lattice rotation around the transverse direction(TD)of the sample.The existence of the grain boundary gave rise to dislocation pile-up in its vicinity,leading to much larger TD-lattice rotations within the boundary region compared to the bulk.With increasing temperature,the deformation was generally more uniform towards the bulk due to enhanced dislocation mobility and more uniform stress distribution.Dynamic recrystallization at 200℃was initiated in{1011}-compression twins at strains of 40%and higher.At 400℃,DRX consumed the entire grain boundary region and gradually replaced the deformed microstructure with progressing deformation.The recrystallized grains displayed characteristic orientations,such that their c-axes were perpendicular to the TD and additionally scattered between 0°and 60°from the loading axis.These recrystallized grains displayed mutual rotations of up to 30°around the c-axes of the initial grains,forming a discernible basal fiber texture component,prominently visible in the{1120}pole figure.It is noteworthy that the deformation and DRX behaviors of the two analyzed bicrystals exhibited marginal variations in response to strain and deformation temperature.

Research on elevated temperature deformation behavior of Ti-6Al-4V sheets

Hot deformation behaviors were studied by means of scanning electron microscopy （SEM） and uniaxial thermal tension. The effect of deformation temperature and strain rate on flow stress was evaluated, and deformation mechanism was analyzed. The results show that the stress-strain curves of Ti-6Al-4V （TC4） alloy sheet and TC4 alloy bar at elevated temperatures have different forms and rules. Flow stress of TC4 is controlled by both strain rate and deformation temperature. The flow stress decreases with the increase of high temperature. Deformation mechanisms exhibit dynamic recovery and recrystallization feature within high temperature region and grain boundary slip behaviors at low temperature.

Weakened anisotropy of mechanical properties in rolled ZK60 magnesium alloy sheets with elevated deformation temperature

The rolling direction（RD） and the transverse direction（TD） samples were obtained from an as-rolled ZK60 magnesium alloy sheet with strong anisotropy of initial texture and their mechanical properties were tested at various deformation temperatures. Meanwhile, the microstructure and texture of these samples after fracture were investigated. Results revealed that a higher flow stress along the RD than that along the TD at room temperature were ascribed to the strong anisotropy of transitional texture, and this texture effect was remarkably weakened with the increase of deformation temperature. Deformation structure was dominant at 100℃, and was replaced by dynamic recrystallization structure when the deformation temperature increased to 200℃ and 300℃. The texture presented a strong texture（transitional texture in the RD sample and basal texture in the TD sample） at 100℃, but its intensity visibly decreased and texture components became more disperse at 200℃ and 300℃. These microstructure and texture results were employed in conjunction with calculated results to argue that raising deformation temperature could increase the activity of non-basal slip by tailoring the relative critical resolved shear stress of each deformation mode and finally result in low texture effect on mechanical anisotropy.

Transformation of low carbon steel during deformation at γ/α temperature based on online rolling data

Alloying elements, such as silicon and manganese, have a major impact on the phase transformation point of steel. Specifically, manganese is an element for the expansion and stability of the austenite region, while silicon can expand and stabilize the ferrite region. Phase transformation occurs during the hot rolling process for the steel with certain silicon content, which leads to great changes of the deformation resistance, thereby affecting the rolling stability. Consequently, a better understanding of phase transformation in the rolling process will contribute to the enhancement of product quality. In this paper ,the on-line rolling data were processed by means of the inverse calculation method. In this method, the steel deformation resistance with various silicon and manganese contents was obtained and analyzed to determine the deformation behavior of the steel, which can help improve the on-line control model and enhance the steel quality.

Effects of γ-irradiation and Deformation Temperature on Tensile Properties of Pb-2 mass% Sb Alloy

Effects ofγ-irradiation and deformation temperature（T）on the tensile properties of Pb-2mass% Sb alloys were studied.The samples were annealed at 458 Kfor 2hin air,then water quenched after they wereγ-irradiated（the different doses were 0.5,1.0,1.5,and 2.0 MGy）.The tensile properties were performed using stress-strain measurements at a constant strain rate（1.2×10^（-3） s^（-1））and at different T（303-393K）.It was found that at constant dose,the fracture stress（σF）decreases while the fracture strain（εF）increases as Tincreases.At particular T,σFincreases whileεFdecreases with increasing dose.The strain-hardening exponent（n）,which is the slope of the relation between ln（σ）and ln（ε）of the parabolic part of the stress-strain curve,was determined and its values increase as Tincreases and decrease as the dose increases.The value of the activation energy increases as the dose increases from 0.07 eV for un-irradiated sample to 0.1eV for the 2 MGy-irradiated sample.These values are in accordance with that needed for dislocation movement and ordering process.An interpretation of the results was given,based on the creation of point and line defects due toγ-irradiation,and that results in a distribution of beta phase（Sb-phase）,leading to a difficulty in the movement of dislocations,so there is an increase in alloy hardness.

Study of High Temperature Deformation and Recrystallization in W9Mo3Cr4V Steel

The behavior of high temperature deformation and recrystallization of W9Mo3Cr4V steel have been studied in this paper. Dynamic precipitation during deformation has also been investigated. In W9Mo3Cr4V steel, stress strain curves exhibit many features. The deformation structures and the effects of deformation parameters on dynamic recrystallization are more complicated than those in low alloy steels. For W9Mo3Cr4V steel, there is a large number of residual carbides on the matrix at high temperature. Also, many second carbides precipitate from the matrix during high temperature deformation. These two kinds of carbides (especially the latter) make the behavior of deformation and dynamic recrystallization in W9Mo3Cr4V steel different from those in low alloy steels. ABSTRACT:The behavior of high temperature deformation and recrystallization of W9Mo3Cr4V steel have been studied in this paper. Dynamic precipitation during deformation has also been investigated. In W9Mo3Cr4V steel, stress strain curves exhibit many features. The deformation structures and the effects of deformation parameters on dynamic recrystallization are more complicated than those in low alloy steels. For W9Mo3Cr4V steel, there is a large number of residual carbides on the matrix at high temperature. Also, many second carbides precipitate from the matrix during high temperature deformation. These two kinds of carbides (especially the latter) make the behavior of deformation and dynamic recrystallization in W9Mo3Cr4V steel different from those in low alloy steels.

Research on synchronous measurement technique of temperature and deformation fields using multispectral camera with bilateral telecentric lens

The hot-section parts easily occur the creep-fatigued interaction under the condition of mechanicalthermal coupled load during the period of service, which may lead to the damage of the parts, and therefore, the measurement and characterization of thermal-deformed fields of the parts are important to understand its damage process. Aiming at relevant demand, the bilateral telecentric-multispectral imaging system was established, the research of synchronous measurement technique of the temperature and deformation fields was developed. On the one hand, the measurement technology for surface temperature of the object was developed using the two-color images captured by the multispectral camera with bilateral telecentric lens and combined with colorimetric method. On the other hand, the 2 D-DIC measurement technique of the multispectral camera was developed by conducting digital image correlation analysis using the blue light images before and after deformation, which can measure the high temperature deformation field of the object(the blue light images were filtered by multispectral camera).Results showed that the bilateral telecentric lens is used to replace the ordinary optical lens for imaging,which can effectively eliminate the distortion of the multispectral imaging system. Since the temperature measurement process of this measurement system is little affected by the emissivity of the object, therefore, it has excellent robustness. The thermal expansion coefficients of the nickel alloys are evaluated at the temperature ranges of 700–1000℃, indicating this system can achieve the synchronous and precise measurement of the temperature and deformation fields of the object.

DEFORMATION BEHAVIOR OF FeAl INTERMETALLIC ALLOY AT ELEVATED TEMPERATURES

ＤＥＦＯＲＭＡＴＩＯＮＢＥＨＡＶＩＯＲＯＦＦｅＡｌＩＮＴＥＲＭＥＴＡＬＬＩＣＡＬＬＯＹＡＴＥＬＥＶＡＴＥＤＴＥＭＰＥＲＡＴＵＲＥＳ①ＬｉＤｉｎｇｑｉａｎｇ，ＬｉｎＤｏｎｇｌｉａｎｇａｎｄＬｉｕＹｉＤｅｐａｒｔｍｅｎｔｏｆＭａｔｅｒｉａｌｓＳｃｉｅｎｃ...

HIGH TEMPERATURE DEFORMATION BEHAVIOR OF TiAl INTERMETALLIC COMPOUND

The behavior of TiAl interrnetallic compound of Ll_0 type under compressive deformation at high temperatures and its recrystallization microstructure have been studied.The compressive proof stress of the polycrystalline TiAl was found to be positive temperature dependence as same as the single crystai one.The correlation of the flow stress together with strain rate and deformation temperature is in good agreement with the expression: ε=Aσ_p^nexp(-Q/RT) Adjusting the deformation temperature and strain rate to a decrease in flow stress of alloy down to below its brittle fracture stress may improve successfully not only the hot working of the TiAl-base alloy but also the fineness of the recrystallized grains.

High Temperature Deformation of Al_2O_3/Cu Composites

This work concerns with the high temperature deformation of internally oxidized Al2O3/Cu com-posites The investigation revealed that dispersive alumina can obstruct dislocation sliding and define the subgrain size thereby improve significantly the strength of the materials at high tem-perature. The sliding of dislocations is a main deformation mechanism in the given temperature range. The sliding of grain boundary and diffusive creep play important roles at high temperature and low strain rate. The dispersoids can raise the recrystallization temperature to higher than 1223 K. Dynamic recovery is a main softening way under the experimental conditions. Higher deformation rate and lower deformation temperature imply a higher flow stress.

Study on Damage of High Temperature Plastic Deformation for Al-Li A lloy

The security of use for Al-Li alloy will be greatly influenced by the damage degree of plastic deformation within i t at high temperature . Based on continuum damage mechanics theory, the damage e volution of Al-5.44Mg-2.15Li-0.12Zr alloy during plastic deforming at high te mperature is simulated by using the damage evolution model of high temperature p lastic deformation. The changing rule of its inner damage with deformation tempe rature, strain rate and strain is gained in this paper. The equation of damage e volution for high temperature plastic deformation is developed, providing an aca demic basis for the technology of plastic process of Al-Li alloys.

Simulation-Based Investigation of Crack Formation in Forged MB15 Magnesium Alloy

In the process of riveting an MB15 forging die,cracks were discovered emerging along the longitudinal direction and near the riveting hole.Through fracture analysis,microscopic observation,energy spectrum analysis,metallographic examination,and hardness test,the properties and causes of the cracks are discussed.The results indicate that the cracking type is intergranular brittle cracking,occurring during the forging stage.Furthermore,the recrystallization at the crack site is found to be incomplete,which is attributed to the low deformation temperature.

Effects of Deformation Conditions on Dynamic Recrystallization of a Nb Microalloyed Anti-seismic Rebar

The hot deformation behavior of a Nb microalloyed anti-seismic rebar was investigated at deformation temperatures of 950-1 100 ℃ and strain rates of 0. 01-0. 1 s- 1 on a Gleeble-3800 thermo-mechnical simulator. The flow stress-strain curves show the typical dynamic recrystallization with a peak,before reaching the steady state flow at higher deformation temperatures and lower strain rates. The constitutive equation governing the dynamic recrystallization( DRX) was obtained and the average activation energy of deformation was calculated as Q = 389. 5 kJ / mol by the regression analysis. The DRX grain size was also found to decrease with the increasing strain rate and the decreasing deformation temperature. The austenite grain size was refined from 118. 0 μm to 15. 07-40. 01 μm by DRX. The DRX grain size under diverse deformation conditions predicted by mathematical model agrees well with experimental results.

High Temperature Strain Structures and Quartz C-Axis Fabrics from Mylonitic Rocks in the Ailaoshan-Red River Shear Zone,Yunnan,and Their Tectonic Implication

The Ailaoshan-Red River（ASRR） shear zone is one of the major Southeast Asian tectonic discontinuities that have figured the present tectonic framework of the eastern Tibet.Several metamorphic massifs are distributed linearly along the shear zone,e.g.Xuelongshan,Diancangshan, Ailaoshan and Day Nui Con Voi from north to south.They bear a lot of lines of evidence for the tectonic evolution of the eastern Tibetan at different crustal levels in different tectonic stages.Controversy still exists on the deformation structures,microstructures and their relationship with metamorphisms along the ASRR.In this paper detailed microstructural and EBSD（Electron Backscattered Diffraction） fabric analysis of some highly sheared granitic rocks from different massifs along the ASRR are conducted.High temperature structures and microstructures are preserved in unsheared gneisses,in weakly sheared xenoliths or in some parts of the highly sheared rocks（mylonites）.Several types of high temperature quartz c-axis fabrics show symmetrical patterns or transitions from symmetrical to asymmetrical patterns.The former are attributed to coaxial deformation during regional shortening in an early stage of the Indian-Eurasian tectonic interaction and the latter are related to the transitions from coaxial compression to noncoaxial shearing during the post-collisional ASRR left lateral shearing.

Effect of temperature on the mechanical abnormity of the quasicrystal reinforced Mg-4%Li-6%Zn-1.2%Y alloy

The serrated phenomena of the quasicrystalline phase reinforced Mg-4%Li-6%Zn-1.2%Y alloy after the extrusion,solid solution treatment and aged treatment have been investigated at different temperatures.The result shows that when the temperature is above 100℃,the serrated phenomenon becomes weak and all the serrated amplitudes are lower than 1 MPa.Among them,the serrated amplitude of samples in aged condition is the lowest and the value is only 0.1-0.2 MPa.The underneath mechanism for the lower plastic instability at higher temperature(≥100℃)can be ascribed to the weak pining effect of solute atoms on the movement of dislocation and release of the pile-up dislocations.

Behavior of AISI 316L Steel Subjected to Uniaxial State of Stress at Elevated Temperatures

This paper presents an experimental investigation on an AISI 316L stainless steel regarding mechanical properties and short uniaxial creep tests at elevated temperatures. The short time creep tests were carried out under different but constant stresses. The obtained data of ultimate tensile strength, yield strength, creep curves and effects of elevated temperatures on mechanical properties were presented. For a selected rheological model, material parameters were obtained. As a justification, such rheological model is implemented in the finite element procedure for an uniaxially stressed specimen in selected environmental conditions.

Prediction of flow stresses at high temperatures with artificial neural networks

On the basis of the data obtained on Gleeble 1500 Thermal Simulator, the predicting models for the relation between stable flow stress during high temperature plastic deformation and deformation strain, strain rate and temperature for 1420 Al Li alloy have been developed with BP artificial neural networks method. The results show that the model on basis of BPNN is practical and it reflects the actual feature of the deforming process. It states that the difference between the actual value and the output of the model is in order of 5%. [

Hot Deformation Kinetics of Magnesium Alloy AZ31

The flow stress at elevated temperatures for magnesium alloy AZ31 was studied using isothermal compression testing. The effect of deformation paranwters on the flow stress was studied aa well. The kinetics of elevated temperature deformation was expressed by means of some empirical rate equations. The activation parameter has been calculated. A mechanism for the dynamic softening of AZ31 alloy in a hot deformation experiment was identified to be the dynamic recrystallization.

Modeling Kinetics of Deformation Induced Ferrite Transformation in Fe-C-Mn Alloy

The influence of hot deformation on the incubation period of ferrite transformation was calculated to determine the onset of deformation induced transformation. Temperature A r3d depends on deformation condition and alloying composition, and decreases with increasing carbon content. When deformation induced ferrite transformation occurs, the flow curves of dislocation density will show strong softening characteristic. Through temperature heavy deformation, ferrite transformation is enhanced and more volume fraction is obtained. The simulated results are in good agreement with the experiment ones.