scholarly journals Microstructure and Texture Evolution of Mg–Gd–Y–Zn–Zr Alloy by Compression–Torsion Deformation

Materials ◽  
2019 ◽  
Vol 12 (17) ◽  
pp. 2773 ◽  
Author(s):  
Ping Xu ◽  
Jianmin Yu ◽  
Zhimin Zhang
Keyword(s):  
Dynamic Recrystallization ◽  
Strain Rate ◽  
Texture Evolution ◽  
Continuous Dynamic Recrystallization ◽  
Recrystallization Mechanism ◽  
Torsion Unit ◽  
Continuous Dynamic ◽  
Gleeble 3500 ◽  
Torsion Deformation ◽  
Zr Alloy

Mg–13Gd–4Y–2Zn–0.5Zr alloy was subjected to compression–torsion deformation at 450 °C with a strain rate of 0.001–0.5 s−1 using a Gleeble 3500 torsion unit. The effects of compression–torsion deformation on the microstructure and texture were studied, and the results showed that with the decrease of strain rate, the texture strength decreased, the number of dynamic precipitated particles increased, the degree of recrystallization increased, and the dynamic recrystallization mechanism changed from a continuous dynamic recrystallization mechanism to a continuous and discontinuous dynamic recrystallization mechanism. Along the direction of increasing radius, the degree of dynamic recrystallized grain (DRX) increased, the number of dynamic precipitated particles increased, and the texture strength slightly increased.

Hot Compression Deformation Behavior of Mg-Gd-Y-Zn-Zr Alloy

2014 ◽  
Vol 680 ◽  
pp. 15-22 ◽  
Author(s):  
Guang Lu ◽  
Zhi Ping Xie ◽  
Zhi Min Zhang ◽  
Yong Biao Yang ◽  
Bao Cheng Li
Keyword(s):  
Flow Stress ◽  
Magnesium Alloy ◽  
Dynamic Recrystallization ◽  
Strain Rate ◽  
Great Influence ◽  
Peak Stress ◽  
Maximum Error ◽  
Continuous Dynamic Recrystallization ◽  
Stress Behaviors ◽  
Continuous Dynamic

The deformation behaviors of as-cast Mg-11Gd-2Y-Zn-Zr magnesium alloy were investigated by compression test with Gleeble-1500 thermal simulator at temperature of 623-753K and strain rate of 0.01-0.5 s-1. The flow stress behaviors of the magnesium alloy were carried out at a strain of 0.7. The strain rate and deformation temperature had great influence on the flow stress behaviors. The flow stress increases with increasing strain rate and decreasing temperature. The flow stress has more than one peak stress at a strain rate of 0.5s-1showing continuous dynamic recrystallization (DRX) mechanism, while other flow stresses exhibited only one peak stress indicating discontinuous dynamic recrystallization (DDRX) mechanism. It was also found that the flow stress behavior could be described by the hyperbolic sine constitutive equation, in which the determined average activation energy is 273.426 kJ·mol-1. The maximum error value between calculated value and experimental value is 5.5%. The deformation map was also established, and the best parameter for hot working was found to be 0.1s-1/753k approximately.

scholarly journals Strain Compensation Constitutive Model and Parameter Optimization for Nb-Contained 316LN

Metals ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 212 ◽  
Author(s):  
Jingdan Li ◽  
Jiansheng Liu
Keyword(s):  
Flow Stress ◽  
Constitutive Model ◽  
Dynamic Recrystallization ◽  
Strain Rate ◽  
Compression Tests ◽  
Continuous Dynamic Recrystallization ◽  
Transmission Electron ◽  
Strain Compensation ◽  
Temperature Ranges ◽  
Continuous Dynamic

Hot deformation behavior of Nb-contained 316LN was investigated using a series of compression tests performed on a Gleeble-1500D simulator at temperature of 950–1200 °C and strain rate of 0.01~1 s−1. Based on the strain compensation method, a modified Arrhenius constitutive model considering the comprehensive effects of temperature, strain rate, and strain on flow stress was established, and the accuracy of the proposed model was evaluated by introducing correlation coefficient (R) and average relative error (AARE). The values of R and AARE were calculated as 0.995 and 4.48%, respectively, proving that the modified model has a high accuracy in predicting the flow stress of Nb-contained 316LN. The microstructure evolution and the dynamic recrystallization (DRX) mechanism of the experimental material were explicated by optical microscopy (OM), electron back scattered diffraction (EBSD), and transmission electron microscopy (TEM). It was found that continuous dynamic recrystallization (CDRX) characterized by subgrain evolution and discontinuous dynamic recrystallization (DDRX) featured by grain boundary nuclei are two main dynamic recrystallization (DRX) mechanisms of Nb-contained 316LN. Furthermore, based on the results of microstructure analyses, optimum parameters were obtained as temperature ranges of 1100~1200 °C and strain rate ranges of 0.01~1 s−1.

scholarly journals Effect of Decreasing Temperature Reciprocating Upsetting-Extrusion on Microstructure and Mechanical Properties of Mg-Gd-Y-Zr Alloy

Metals ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 985
Author(s):  
Wenlong Xu ◽  
Jianmin Yu ◽  
Guoqin Wu ◽  
Leichen Jia ◽  
Zhi Gao ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Dynamic Recrystallization ◽  
Combined Effect ◽  
Second Phase ◽  
Basal Texture ◽  
Continuous Dynamic Recrystallization ◽  
Texture Intensity ◽  
Fine Grain ◽  
Continuous Dynamic ◽  
Zr Alloy

The decreasing temperature reciprocating upsetting-extrusion (RUE) deformation experiment was carried out on Mg-Gd-Y-Zr alloy to study RUE deformation on the influence of microstructure of the alloy. This work showed that with the gradual increase of RUE deformation passes, the continuous dynamic recrystallization (CDRX) process and the discontinuous dynamic recrystallization (DDRX) process occurred at the same time, and the grain refinement effect was obvious. Particulate precipitation induced the generation of DRX through particle-stimulated nucleation (PSN). In addition, after one pass of RUE deformation, the alloy produced a strong basal texture. As the RUE experiment proceeded, the basal texture intensity decreased. The weakening of the texture was due to the combined effect of DRX and alternating loading forces in the axial and radial directions. After four RUE passes, the mechanical properties of the alloy had been significantly improved, which was the result of the combined effect of dislocation strengthening, fine grain strengthening, and second phase strengthening.

Geometric Dynamic Recrystallization in an AA2219 Alloy Deformed to Large Strains at an Elevated Temperature

2004 ◽  
Vol 467-470 ◽  
pp. 1199-1204 ◽  
Author(s):  
Rustam Kaibyshev ◽  
I. Mazurina ◽  
Oleg Sitdikov
Keyword(s):  
Dynamic Recrystallization ◽  
Equal Channel Angular Extrusion ◽  
Large Strains ◽  
Specific Process ◽  
Continuous Dynamic Recrystallization ◽  
Aa2219 Alloy ◽  
Continuous Dynamic ◽  
The Stability ◽  
Average Size ◽  
Zr Alloy

The mechanism of new grain evolution during equal channel angular extrusion (ECAE) up to a total strain of ~12 in an Al-Cu-Mn-Zr alloy at a temperature of 475oC (0.75Tm) was examined. It was shown that the new grains with an average size of about 15 µm result from a specific process of geometric dynamic recrystallization (GRX) which can be considered as a type of continuous dynamic recrystallization (CDRX). This process involves three elementary mechanisms. At moderate strains, extensive elongation of initial grains takes place; old grain boundaries become progressively serrated. Upon further ECAE processing, transverse low-angle boundaries (LAB) with misorientation ranging from 5 to 15o are evolved between grain boundary irregularities subdividing the initial elongated grains on crystallites with essentially equiaxed shape. The misorientation of these transverse subboundaries rapidly increases with increasing strain, resulting in the formation of true recrystallized grains outlined by high-angle boundaries from all sides. In the same time, the average misorientation of deformation-induced boundaries remains essentially unchanged during ECAE. It is caused by the fact that the evolution of LABs with misorientation less than 4o occurs continuously during severe plastic deformation. The mechanism maintaining the stability of the transverse subboundaries that is a prerequisite condition for their further transformation into highangle boundaries (HABs) is discussed.

Regularities of Grain Refinement in an Austenitic Stainless Steel during Multiple Warm Working

2013 ◽  
Vol 753 ◽  
pp. 411-416 ◽  
Author(s):  
Andrey Belyakov ◽  
Marina Tikhonova ◽  
Zhanna Yanushkevich ◽  
Rustam Kaibyshev
Keyword(s):  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Dynamic Recrystallization ◽  
Strain Rate ◽  
Structural Changes ◽  
Continuous Dynamic Recrystallization ◽  
Warm Working ◽  
Fine Grain ◽  
Power Law Function ◽  
Continuous Dynamic

The structural changes that are related to the new fine grain development in a chromium-nickel austenitic stainless steel subjected to warm working by means of multiple forging and multiple rolling were studied. The multiple warm working to a total strain of 2 at temperatures of 500-900C resulted in the development of submicrocrystalline structures with mean grain sizes of 300-850 nm, depending on processing conditions. The new fine grains resulted mainly from a kind of continuous reactions, which can be referred to as continuous dynamic recrystallization. Namely, the new grains resulted from a progressive evolution of strain-induced grain boundaries, the number and misorientation of which gradually increased during deformation. In contrast to hot working accompanied by discontinuous dynamic recrystallization, when the dynamic grain size can be expressed by a power law function of temperature compensated strain rate as D ~ Z-0.4, much weaker temperature/strain rate dependence of D ~ Z-0.1was obtained for the warm working.

scholarly journals Microstructure and Texture Evolution of AZ31 Alloy Prepared by Cyclic Expansion Extrusion with Asymmetrical Extrusion Cavity at Different Temperatures

Materials ◽  
2020 ◽  
Vol 13 (17) ◽  
pp. 3757
Author(s):  
Jie Zheng ◽  
Zhaoming Yan ◽  
Qiang Wang ◽  
Zhimin Zhang ◽  
Yong Xue
Keyword(s):  
Dynamic Recrystallization ◽  
Texture Evolution ◽  
Az31 Alloy ◽  
Continuous Dynamic Recrystallization ◽  
Initial Stage ◽  
Cumulative Strain ◽  
Coarse Grains ◽  
Different Temperatures ◽  
Continuous Dynamic ◽  
Equiaxed Grains

This work is to study the microstructure and texture evolution of AZ31 alloy prepared by cyclic expansion extrusion with an asymmetrical extrusion cavity (CEE-AEC) at different deformation temperatures. The result shows AZ31 alloy undergoes continuous dynamic recrystallization (CDRX) and discontinuous dynamic recrystallization (DDRX) during CEE-AEC processing. At the initial stage of deformation, AZ31 alloys exhibit similar bimodal microstructure of coarse deformed grains surrounded by fine DRXed grains. As the passes increase, the cumulative strain increases, and the coarse grains of all samples are almost replaced by fine equiaxed grains. The average grain sizes and the basal texture intensities of the deformed samples increase as the deformation temperature increases. In addition, due to the existence of an asymmetrical cavity, as the passes increase, the basal textures of all samples are deflected with maximum intensities increase, and even an unusual bimodal texture is formed, resulting in a soft orientation that is easy to basal slip.

Analysis of Large Strain Hot Torsion Textures Associated With “Continuous” Dynamic Recrystallization

2008 ◽  
Vol 131 (1) ◽  
Author(s):  
S. M. Lim ◽  
C. Desrayaud ◽  
F. Montheillet
Keyword(s):  
Grain Boundary ◽  
Dynamic Recrystallization ◽  
Large Strain ◽  
Texture Evolution ◽  
Boundary Migration ◽  
Grain Boundary Migration ◽  
Shear Direction ◽  
Continuous Dynamic Recrystallization ◽  
Hot Torsion ◽  
Continuous Dynamic

The development of ideal orientations within the steady-state region of hot torsion flow curves of fcc and bcc metals undergoing “continuous” dynamic recrystallization is analyzed. It is well known that in fcc metals, e.g., Al deformed at 400°C and above, the experimentally observed end texture consists of the twin-symmetric B(112¯)[11¯0]/B¯(1¯1¯2)[1¯10] component, whereby the (hkl)[uvw] indices correspond to the shear plane z and the shear direction θ, respectively. In bcc iron however, only one of the self-symmetric D1(112¯)[111] and D2(1¯1¯2)[111] components dominates (the former in the case of positive shear or clockwise rotation about the r-axis, and the latter during negative shear). The tendency toward a single end orientation imposes certain limitations on grain refinement, as this would ultimately imply the coalescence of subgrains of or close to this orientation, and therefore the disappearance of existing high angle boundaries (≥15 deg). It is believed that the preference of D1 over D2, or vice versa, could be related to phenomena other than glide-induced rotations, e.g., grain boundary migration resulting from differences in work hardening rates. In this paper, the standard Taylor model is first used to predict the texture evolution in simple shear under the full-constraint rate-sensitive scheme. This is then coupled with an approach that takes into account grain boundary migration resulting from differences in dislocation densities within grains of varying orientations. The preliminary results are in agreement with experimental findings, i.e., grains with initial orientations close to D2 grow at the expense of neighboring grains during negative shear and vice versa.

scholarly journals A Physically Based Constitutive Model and Continuous Dynamic Recrystallization Behavior Analysis of 2219 Aluminum Alloy during Hot Deformation Process

Materials ◽  
2018 ◽  
Vol 11 (8) ◽  
pp. 1443 ◽  
Author(s):  
Lei Liu ◽  
Yunxin Wu ◽  
Hai Gong ◽  
Shuang Li ◽  
A. S. Ahmad
Keyword(s):  
Constitutive Model ◽  
Dynamic Recrystallization ◽  
Strain Rate ◽  
Hot Deformation ◽  
Flow Behavior ◽  
Large Strains ◽  
Al Alloy ◽  
Continuous Dynamic Recrystallization ◽  
Physically Based ◽  
Continuous Dynamic

The isothermal compression tests of the 2219 Al alloy were conducted at the temperature and the strain rate ranges of 623–773 K and 0.01–10 s−1, respectively, and the deformed microstructures were observed. The flow curves of the 2219 Al alloy obtained show that flow stress decreases with the increase in temperature and/or the decrease in strain rate. The physically based constitutive model is applied to describe the flow behavior during hot deformation. In this model, Young’s modulus and lattice diffusion coefficient are temperature-dependent, and the creep exponent is regarded as a variable. The predicted values calculated by the constitutive model are in good agreement with the experimental results. In addition, it is confirmed that the main softening mechanism of the 2219 Al alloy during hot deformation is dynamic recovery and incomplete continuous dynamic recrystallization (CDRX) by the analysis of electron backscattered diffraction (EBSD) micrographs. Moreover, CDRX can readily occur under the condition of high temperatures, low strain rates, and large strains. Meanwhile, the recrystallization grain size will also be larger.

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