Hot deformation behavior of novel high-strength Mg-0.6Mn-0.5Al-0.5Zn-0.4Ca alloy

The hot compression behavior of as-extruded Mg-0.6Mn-0.5Al-0.5Zn-0.4Ca alloy was studied on a Gleeble-3500 thermal simulation machine.Experiments were conducted at temperatures ranging from 523 to 673 K and strain rates ranging from 0.001 to 1 s^(-1).Results showed that an increase in the strain rate or a decrease in deformation temperature led to an increase in true stress.The constitutive equation and processing maps of the alloy were obtained and analyzed.The influence of deformation temperatures and strain rates on microstructural evolution and texture was studied with the assistance of electron backscatter diffraction(EBSD).The as-extruded alloy exhibited a bimodal structure that consisted of deformed coarse grains and fine equiaxed recrystallized structures(approximately 1.57μm).The EBSD results of deformed alloy samples revealed that the recrystallization degree and average grain size increased as the deformation temperature increased.By contrast,dislocation density and texture intensity decreased.Compressive texture weakened with the increase in the deformation temperature at the strain rate of 0.01 s-1.Most grains with{0001}planes tilted away from the compression direction(CD)gradually.In addition,when the strain rate decreased,the recrystallization degree and average grain size increased.Meanwhile,the dislocation density decreased.Texture appeared to be insensitive to the strain rate.These findings provide valuable insights into the hot compression behavior,microstructural evolution,and texture changes in the Mg-0.6Mn-0.5Al-0.5Zn-0.4Ca alloy,contributing to the understanding of its processing-microstructure-property relationships.

Hot deformation behavior and microstructure evolution of Be/2024Al composites

The high temperature compression test of Be/2024Al composites with 62wt%Be was conducted at 500–575℃ and strain rate of0.003–0.1 s^(-1).The strain-compensated Arrhenius model and modified Johnson–Cook model were introduced to predict the hot deformation behavior of Be/2024Al composites.The result shows that the activation energy of Be/2024Al composites was 363.364 k J·mol^(-1).Compared with composites reinforced with traditional ceramics,Be/2024Al composites can be deformed with ultra-high content of reinforcement,attributing to the deformable property of Be particles.The average relative error of the two models shows that modified Johnson–Cook model was more suitable for low temperature condition while strain-compensated Arrhenius model was more suitable for high temperature condition.The processing map was generated and a hot extrusion experiment was conducted according to the map.A comparation of the microstructure of Be/2024Al composites before and after extrusion shows that the Be particle deformed coordinately with the matrix and elongated at the extrusion direction.

Deformation behavior and microstructure of an Al-Zn-Mg-Cu-Zr alloy during hot deformation

The hot deformation behavior and microstructures of Al-7055 commercial alloy were investigated by axisymmetric hot compres- sion at temperatures ranging from 300℃ to 450℃ and strain rates from 10^-2 to 10 s^-1, respectively. Microstructures of deformed 7055 alloy were investigated by transmission electron microscopy （TEM）. The dependence of peak stress on deformation temperature and strain rate can be expressed by the hyperbolic-sine type equation. The hot deformation activation energy of the alloy is 146 kJ/mol. Moreover, the flow stress curves predicted by the modified constitutive equations are reasonably consistent with the experimental results, which confirms that the proposed deformation constitutive equations can provide evidence for the selection of hot forming parameters. TEM results indicate that dy- namic recovery is the main softening mechanism during hot deformation.

Deformation Behavior and Microstructure Evolution of Wrought Magnesium Alloys

There are many researches on the deformation behavior of wrought magnesium alloys, such as AZ31, AZ80, AZ91, and ZK60 magnesium alloys at different temperatures and strain rates, but few of them focuses on the deformation behavior of AZ41M and ZK60M alloys, especially under the twin-roll casting (TRC) state. Meanwhile, the existing researches only focus on the grain refinement law of the magnesium alloys under deformation conditions, the deformation mechanism has not been revealed yet. The hot compression behavior of AZ41M and ZK60M magnesium alloys under the temperature and strain rate ranges of 250-400 ℃ and 0.001-1 s-1 are studied by thermal simulation methods using Gleeble 1500 machine and virtual simulation using finite element analysis software. Simulation results show that sine hyperbolic law is the most suitable flow stress model for wider deformation conditions. The most reasonable selected deformation conditions of ZK60M alloy is 350 oC/0.1 s-1 for TRC and 350 oC/1 s-1 for conventional casting (CC), while AZ41M alloy is 300 oC/0.01 s-1 for TRC and 350 oC/0.1 s-1 for CC. Deformation behavior and dynamic recrystallization (DRX) mechanism of them are analyzed at the same deformation conditions. The microstructures of AZ41M and ZK60M alloys are observed at different deformed conditions by optical microscopy (OM) and electron back scatter diffraction (EBSD) and it reveals the flow behavior and deformation mechanism of them. Working harden and work soften contribute to the activation of basal, non-basal slip systems which promote DRX. The proposed research reveals the deformation behavior and mechanism of the AZ41M and ZK 60M magnesium alloys and concludes their optimized deformation parameters and processes and provides a theory basis for their manufacturing and application.

Effect of 1Al addition on deformation behavior of Mg

Deformation behavior of 1 Al containing Mg alloy has been investigated in the present study.After annealing,the Mg-1 Al alloy shows a typical basal texture.When compared to the pure Mg having a similar texture and grain size,the Mg-1 Al alloy shows much higher strength and larger elongation.Slip trace analyses of the tensile strained specimens show that non-basal slips such as pyramidal I and II slips can be easily activated at an early stage of deformation in the Mg-1 Al alloy and the grains in the Mg-1 Al alloy are seen to accommodate a larger degree of deformation than those in the pure Mg at a given strain.With increasing tensile strain,however,there is a strain localization along the initially formed slip lines of non-basal slips,forming surface steps without activating multiple slip lines.

Study on the Deformation Behavior of Mg-3.6%Er Magnesium Alloy

The deformation behaviour of a casting Mg-3.6% Er magnesium alloy after T6 treatment was studied in tensile tests from room temperature to 450 ℃ under different strain rates ranging from 1.0 ×10^-4 to 6.0 × 10^-3 S^-1 Obtained local plateau in the temperature dependence of the ultimate strength （σb） and yield strength （σ0.2） under constant strain rate indicated the presence of dynamic strain ageing （DSA）. Serrated flow was observed at the temperature of 200, 250, and 300 ℃. The observed negative strain rate sensitivity suggested that the serrated flow behavior arose from DSA. The temperature and strain rate dependence of the critical strain for the onset of serrated flow was analyzed using a phenomenological DSA equation, and the apparent activation energy Q for the serrated flow was obtained by calculation.

Superplastic Deformation Behavior of Hot-rolled AZ31 Magnesium Alloy Sheet at Elevated Temperatures

Uniaxial tensile tests were carride out in the temperature range of 250-450℃ and the strain rate range of 0.7×10^-3^-1.4×10^-1s^-1 to evaluate the superplasticity of AZ31 Mg aloy .The threshold stress which characterizes the difficulty for grain boundary sliding was calculated at various temperature .The surface relieves of superplastically deformed specimens were observde by using a scanning elctronic microscops （SEM）.Results show that ,at the temperature of 400℃ and strain rate of 1.7×10^-3^-1,the strain rate sensitivity exponent ,i e,m value reaches 0.47 and the maximum elongation of 362.5% is achieved .Grain boundary sliding （GBS）is the primary deformation mechanism and characterized by a pronounced improvement in the homogeneity with increasing temperatures.A large number of filaments were formed at the end of deformation and intergranular cavities produced with the necking and fracture of filaments.Finally ,the model for the formation of intergranular cavities was proposed.

Influence of Transverse Normal Pressure on Deformation Behavior of Sheet Metal

To investigate the influence of magnitude and distribution of the transverse normal pressure on deformation behavior of sheet metal,viscous pressure bulge test (VPB) of overlapping sheet metals is proposed,where the overlapped sheet metal is deformed under the dual-sided normal pressure provided by viscous medium and the overlapping sheet.The transverse normal pressure loading features provided by overlapping sheet metals are first simulated by DEFORM-2D.It shows that the magnitude and space distribution of transverse normal pressure are dependent on strain hardening exponent n-,strength coefficient K-and thickness t-values of the overlapping sheet metal.Based on the stress,deviator stress and strain distribution resulted from the finite element simulation,it indicated that the uniform transverse normal pressure has no effect on deviator stress,the figure and strain distribution of bulge specimens have no change.The non-uniform transverse normal pressure can remarkably change the figure and metal flow of specimens,and the formability of sheet metal can be improved by controlling the transverse normal pressure distribution.

A New Discovery on the Deformation Behavior of Shale Gas Reservoirs Affecting Pore Morphology in the Juhugeng Coal Mining Area of Qinghai Province, Northwest China

Objective The Juhugeng mining area in Qinghai Province of northwest China has attracted wide attention among geologists for it hosts typical coal measure gases.The shale gas reservoirs were reformed by intensive structural movements during geological periods,

Deformation Behavior and Microstructure Evolution of AA2024-H18 Aluminum Alloy by Hot Forming with Synchronous Cooling Operations

Hot forming with synchronous cooling(HFSC)is a novel technique for heat-treatable,high-strength aluminum alloys,which allows the alloys to acquire good formability,negligible springback,rapid processing and better mechanical properties.However,the deformation behavior and microstructure evolution of the alloys during HFSC are complex and need to be studied due to the temperature and strain rate effects.Uniaxial tensile tests in a temperature range of 250—450℃and a strain rate range of 0.01—1 s-1 for AA2024-H18 aluminum alloy sheet are conducted with a Gleeble-3500 Thermal-Mechanical Simulation Tester.And based on metallography observation and analysis,AA2024-H18 aluminum alloy sheet in HSFC process exhibits hardening and dynamic recovery behaviors within the temperature range of 250—450 ℃.Strain rate shows different effects on ductility at different temperatures.Compared with traditional warm/hot forming methods,AA2024-H18 aluminum alloy achieves a better work-hardening result through HFSC operations,which promises an improved formability at elevated temperature and thus good mechanical properties of final part.After HSFC operations,the microstructure of the specimens is composed of elongated static recrystallization grain.

Effects of microrolling parameters on the microstructure and deformation behavior of pure copper

Microrolling experiments and uniaxial tensile tests of pure copper under different annealing conditions were carried out in this paper. The effects of grain size and reduction on non-uniform deformation, edge cracking, and microstructure were studied. The experimen- tal results showed that the side deformation became more non-uniform, resulting in substantial edge bulge, and the uneven spread increased with increasing grain size and reduction level. When the reduction level reached 80% and the grain size was 65 μm, slight edge cracks occurred. When the grain size was 200 μm, the edge cracks became wider and deeper. No edge cracks occurred when the grain size was 200 μm and the reduction level was less than 60%; edge cracks occurred when the reduction level was increased to 80%. As the reduction level increased, the grains were gradually elongated and appeared as a sheet-like structure along the rolling direction; a fine lamellar structure was obtained when the grain size was 20 lam and the reduction level was less than 60%.

Microstructural changes during heating of super duplex stainless steel and its thermal deformation behavior

Microstructural changes during heating of highly alloyed Cr26Ni7 type super duplex stainless steel （SDSS2607） and its thermal deformation behavior were investigated. At different heating rates, the mechanism of phase transition from y phase to 6 phase and growth modes of ~ phase differed. Variations in microstructures for as- cast SDSS2607 during heat preservation at 1 220 ~C indicated two kinds of transformations from y phase to 6 phase. In-situ observations of microstructural changes during the tensile process at 1 050 showed a mutual coordination between y and 6 phases. When the true strain increased, the mutual coordination between 7 and 6 phases was damaged. Subsequently, cracks nucleated at the ＂y/g interface. With the increase in temperature, the strength of as- cast SDSS2607 decreased while its plasticity increased. Its thermoplasticity was poor, and the reduction in area of tensile specimens was less than 80%. When the deformation strain of hot compression increased, the stable deformation zone in the heat processing maps enlarged gradually. Moreover, the unstable deformation zones were extended.

On the deformation behavior of heterogeneous microstructure and its effect on the mechanical properties of die cast AZ91D magnesium alloy

Both a conventional flow distributer and an improved one with a flow buffer were applied respectively during the high pressure die casting(HPDC)process,and samples of AZ91D magnesium alloy with different microstructure mainly consisting ofα-Mg grains,β-phase and porosities were obtained.According to the grain orientation analysis,the predominant deformation behavior inα-Mg grains was dislocation slip,supplemented by deformation twinning.Dislocation slip was more difficult to occur in the samples with the improved flow distributer on account of the fact that the size ofα-Mg grains in the microstructure was finer and more uniform.During the in situ tensile deformation test,cracks were observed to initiate from gas-shrinkage pore and island-shrinkage,and two main crack propagation mechanisms,porosity growth and coalescence were found accordingly.When the crack was in contact with theβ-phase,it would pass through and fracture the networkβ-phase,whereas bypass the islandβ-phase by detaching it from the surroundingα-Mg grains.Mechanical property tests showed that the samples with relatively more homogeneous microstructure would perform higher mechanical properties,which was the combined effect of matrixα-Mg grains,β-phase,and porosities.

Deformation Behavior and Formability of Gradient Nano-grained AISI 304 Stainless Steel Processed by Ultrasonic Impact Treatment

The deformation behavior and formability of gradient nano-grained（GNG） AISI 304 stainless steel in uniaxial and biaxial states were investigated by means of tensile test and small punch test（SPT）. The GNG top layer was fabricated on coarse grains（CG） AISI 304 by ultrasonic impact treatment. The results showed that the CG substrate could effectively suppress the strain localization of NC in GNG layer, and an approximate linear relationship existed between the thickness of substrate（h） and uniform true strain before necking（ε_（unif））. Grain growth of NC was observed at the stress state with high Stress triaxiality T, which led to better ductility of GNG/CG 304 in SPT, as well as similar true strain after the onset of necking（ε_（neck）） compared with coarse 304 in tensile test. Ei-values of GNG/CG 304 with different structures were nearly the same at different punch speeds, and good formability of GNG/CG 304 was demonstrated. However, punch speed and microstructure needed to be optimized to avoid much lost of membrane strain region in biaxial stress state.

Inclusion and its deformation behavior in 304 stainless steel

Non-metallic inclusion is the main reason for the presence of surface defects in cold-rolled steel strip. In this study, the composition, morphology, and size of the non-metallic inclusion in hot-rolled 304 stainless steel strips are analyzed. Cold-rolled 304 stainless steel strips with different cold-rolling reduction have been prepared, and the morphology and size of inclusion in these cold-rolled strips are also analyzed. Furthermore, the deformation behavior of a non-metallic inclusion during the cold-rolling process is studied. The results show that CaO-SiO2- MgO-Al2 O3, a kind of brittle compound oxide,is the main type of inclusion in hot-rolled 304 stainless steel strips. During the cold-rolling process, ductile deformation of this type of inclusion is not obvious, where large inclusions are crushed, and the average size of inclusions in cold-rolled strips decreased while the cold-rolling reduction increased.

Study on the Deformation Behavior of Mg-Gd-Y-Zn-Mn Wrought Magnesium Alloys by Visco-plastic Self-consistent Modeling

The plastic deformation behavior of new Mg-Gd-Y-Zn-Mn magnesium alloys gains great necessity to clarify and understand the mechanism deeply. In the present work,the tensile mechanical property test and visco-plastic self-consistent (VPSC) model are used to investigate the activities of deformation modes of VW84M and VW94M magnesium alloys during the tensile deformation. The results show that the mechanical properties of the above extruded alloys are similar but VW94M has higher strength than VW84M after the same aging process. Compared with the extruded alloys,the as-aged alloys have significantly higher activation of pyramidal slip at the later stage of plastic deformation. In addition,the as-aged VW94M alloy with higher strength has the largest activity of pyramidal slip. In summary,the addition of Gd increases the critical resolved shear stress (CRSS)in each slip system of VW94M,while the increase in the strength and the decrease in the elongation of as-aged alloys are associated with the significant activation of pyramidal slip.

DEFORMATION BEHAVIOR OF FeAl INTERMETALLIC ALLOY AT ELEVATED TEMPERATURES

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Variation in Deformation Behaviors Along the Transverse Direction During the Warm Rolling of a 1480-mm-Wide AZ31B Plate

A decrease in the weight of aerospace vehicles,large ships,weapons,and high-speed trains will increase the demand for wide-width magnesium alloy plates and their composite parts to replace steel and plastic.An investigation was conducted to study the variation in deformation behaviors along the transverse direction during the warm rolling of a 1480-mm-wide AZ31B plate.A uniaxial thermal compression test with a 59%reduction was performed at different positions on a 13.7-mm-thick rolled plate along the width direction at a temperature of 220℃ and 270℃ and strain rate of 15 s^(−1).At the same time,the 13.7-mm-thick plate was rolled in a single pass to 5.6 mm on a mill with a 1725-mm-wide roll to confirm the thermal deformation behavior and the dynamic recrystallization(DRX).The results show that the main texture type does not change and the grain size does not have a clear deflection when the magnesium alloy plate reaches a certain value under rolling accumulative reduction.The grain size of a 13.7-mm-thick plate increases with a decrease in the distance to the center layer in the thickness direction.In the width direction,the edge(R6)first decreases and then increases toward the symmetric plane(R1).The critical stress required for dynamic recrystallization in the transition zone R3 of the rolled plate width is minimum,and the average grain size is minimum owing to the relatively complete recrystallization.

Relation of deformation behavior with precipitation and groundwater of the Babaoshan fault in Beijing

We discuss the influence of precipitation and groundwater on the deformation behavior of the Babaoshan fault of Beijing by using long-term observation data from Dahuichang station during 1970-2003. The results show that a) the pore pressure on fault zone as well as the fault deformation behavior exhibited periodically variation as precipitation changed steadily and periodically; b) the periodicity of the pore pressure of fault zones disappeared and the manner of fault deformation behavior changed when precipitation was small and/or was in aberrance. This implies that rainfall plays a key role in fault deformation behavior through changing the pore pressure of fault zones. Combining the existing results about the Babaoshan fault, it is concluded that precipitation and groundwater may adjust the stress/strain field by controlling the deformation behavior of the fault, which can provide direct observation evidence for the interaction of fluid and solid in shallow crust of the Earth.

Mechanical properties and deformation behavior of Ti-5Al-2.5ZrELI alloy used at cryogenic temperature

The mechanical properties and deformation behavior of Ti 5Al 2.5 ZrELI alloy compared with Ti 5Al 2.5 SnELI at 4.2?K, 20?K and 293?K were investigated. The results show that the new titanium alloy Ti 5Al 2.5ZrELI has more consistent properties because of its uniform microstructure and less segregation. It has good elongation and ductility. The fracture surfaces are covered with elongated dimples at cryogenic temperatures. The deformation mode at 293?K, 20?K and 4.2?K are twinning and slipping. [