scholarly journals Microstructure Heredity of Inconel 718 Nickel-Based Superalloy during Preheating and Following Deformation

Crystals ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 303
Author(s):  
Jianguo Wang ◽  
Dong Liu ◽  
Xiao Ding ◽  
Haiping Wang ◽  
Hai Wang ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Grain Size ◽  
Dynamic Recrystallization ◽  
Inconel 718 ◽  
Volume Fraction ◽  
Effective Strain ◽  
Hot Working ◽  
Solution Temperature ◽  
Compression Tests ◽  
Δ Phase

Preheating and compression tests of Inconel 718 superalloy double cone specimens were carried out to investigate the microstructure heredity during hot working. Optical microscopy, scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and transmission electron microscopy (TEM) were used to characterize the microstructure evolution. The results show that intense microstructure heredity can be found at the temperature 960~990 °C. During the preheating process, δ phase precipitation or grain growth could increase the fraction of high angle grain boundary (HAGBs) and Σ3n boundaries. Otherwise, the generation or spread of annealing twin could increase the fraction of LAGBs, Volume fraction of recrystallized grains was evaluated at the whole hot working process. At the temperature of 960~990 °C, the volume fraction of recrystallized grains increases with effective strain increasing. At the super solution temperature of δ phase, the volume fraction of recrystallized grains decreases and then increases with the increase of the effective strain. The unimodal grain size distribution and fully recrystallized grains can be obtained at low strains at 960~990 °C. The twin boundary length fraction of deformed specimens is always lower than that of preheated ones. Discontinuous dynamic recrystallization (DDRX) was considered as the dominant nucleation mechanism, and continuous dynamic recrystallization (CDRX) was strengthened with the increasing grain size. Twin introduced deformation will be the main deformation mode for alloy 718 with larger grain.

Effect of Initial Microstructure under Different Solidification Conditions on Hot Working Behavior of AZ31 Alloy

2007 ◽  
Vol 561-565 ◽  
pp. 325-328
Author(s):  
L. Shang ◽  
Steve Yue ◽  
Elhachmi Essadiqi ◽  
A. Javaid ◽  
Jon T. Carter ◽  
...  
Keyword(s):  
Grain Size ◽  
Dynamic Recrystallization ◽  
Flow Behavior ◽  
Az31 Alloy ◽  
Hot Working ◽  
Water Cooling ◽  
Compression Tests ◽  
Significant Difference ◽  
Second Phases ◽  
Cast Microstructure

In order to investigate the effect of the as-cast microstructure on the hot working behavior of an AZ31 magnesium alloy, specimens were cast in copper moulds with and without water cooling. A series of compression tests were performed at a temperature of 350 °C, a strain rate of 0.01 s-1, and at strains up to 1.0. It was found that as-cast microstructure is very sensitive to the solidification conditions, which leads to a significant difference in flow behavior and dynamic recrystallization (DRX) characteristics. It appears that more uniform and refined as-cast grain size promotes dynamic recrystallization and reduces the flow stress. It is also possible that second phases (>1+m in size) contribute to DRX by acting as nuclei.

scholarly journals The Formation of 14H-LPSO in Mg–9Gd–2Y–2Zn–0.5Zr Alloy during Heat Treatment

Materials ◽  
2021 ◽  
Vol 14 (19) ◽  
pp. 5758
Author(s):  
Yunfang Liu ◽  
Yaqin Yang ◽  
Ming Yi ◽  
Jianmin Yu ◽  
Baocheng Li ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Heat Treatment ◽  
Grain Size ◽  
Volume Fraction ◽  
Cast Alloy ◽  
Solution Treatment ◽  
Phase Changes ◽  
Solution Temperature ◽  
Second Phase ◽  
Lpso Phase

There is a new long-period stacking ordered structure in Mg–RE–Zn magnesium alloys, namely the LPSO phase, which can effectively improve the yield strength, elongation, and corrosion resistance of Mg alloys. According to different types of Mg–RE–Zn alloy systems, two transformation modes are involved in the heat treatment transformation process. The first is the alloy without LPSO phase in the as-cast alloy, and the MgxRE phase changes to 14H-LPSO phase. The second is the alloy containing LPSO phase in the as-cast state, and the 14H-LPSO phase is obtained by the transformations of 6H, 18R, and 24R. The effects of different solution parameters on the second phase of Mg–9Gd–2Y–2Zn–0.5Zr alloy were studied by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). The precipitation mechanism of 14H-LPSO phase during solution treatment was further clarified. At a solution time of 13 h, the grain size increased rapidly initially and then decreased slightly with increasing solution temperature. The analysis of the volume fraction of the second phase and lattice constant showed that Gd and Y elements in the alloy precipitated from the matrix and formed 14H-LPSO phase after solution treatment at 490 °C for 13 h. At this time, the hardness of the alloy reached the maximum of 74.6 HV. After solution treatment at 500 °C for 13 h, the solid solution degree of the alloy increases, and the grain size and hardness of the alloy remain basically unchanged.

Study on Dynamic Recrystallization Behavior in Deformed Austenite of 52100 Steel by Using JMAK-Model

2013 ◽  
Vol 275-277 ◽  
pp. 1833-1837
Author(s):  
Ke Lu Wang ◽  
Shi Qiang Lu ◽  
Xin Li ◽  
Xian Juan Dong
Keyword(s):  
Grain Size ◽  
Dynamic Recrystallization ◽  
Hot Deformation ◽  
Volume Fraction ◽  
True Strain ◽  
Strain And Strain Rate ◽  
Average Grain Size ◽  
Dynamic Recrystallization Behavior ◽  
Simulation And Experiment ◽  
Good Agreement

A Johnson-Mehl-Avrami-Kolmogorov (JMAK)-model was established for dynamic recrystallization in hot deformation process of 52100 steel. The effects of hot deformation temperature, true strain and strain rate on the microstructural evolution of the steel were physically studied by using Gleeble-1500 thermo-mechanical simulator and the experimental results were used for validation of the JMAK-model. Through simulation and experiment, it is found that the predicted results of DRX volume fraction, DRX grain size and average grain size are in good agreement with the experimental ones.

Recrystallization and Grain Growth during Alloy 718 Processing

2007 ◽  
Vol 539-543 ◽  
pp. 3094-3099
Author(s):  
Nho Kwang Park ◽  
Jeoung Han Kim ◽  
Jong Taek Yeom
Keyword(s):  
Grain Size ◽  
Grain Growth ◽  
Heat Treatments ◽  
Grain Structure ◽  
Alloy 718 ◽  
Compression Tests ◽  
Δ Phase ◽  
Grain Boundary Characteristics ◽  
The Difference ◽  
Boundary Characteristics

In Alloy 718 ingot cogging process, dynamic and metadynamic recrystallizations, and static grain growth occur, and also the presence of δ phase plays a key role in controlling the grain size. In this study, the evolution of grain structure in VIM/VAR-processed Alloy 718 ingots during post-cogging heat treatments is dealt with. Compression tests were made on VIM/VAR-processed Alloy 718 ingot at temperatures between 900oC ~ 1150oC. Heat treatments were made on the compression-tested specimens, and the variation of grain size was evaluated. Constitutive equations for the grain growth are established to represent the evolution of microstructures. Special attention is paid to the evolution of grain structure under the condition of dynamic and metadynamic recrystallizations, and grain growth. The grain growth rate depends mainly on the presence of δ-phase below the δ-solvus temperature, and on the difference in the grain boundary characteristics above it.

Hot Deformation and Dynamic Recrystallization in Titanium Aluminide

2018 ◽  
Vol 941 ◽  
pp. 1391-1396 ◽  
Author(s):  
Nitish Bibhanshu ◽  
Satyam Suwas
Keyword(s):  
Shear Band ◽  
Dynamic Recrystallization ◽  
Titanium Aluminide ◽  
Volume Fraction ◽  
Shear Bands ◽  
Hot Workability ◽  
Compression Tests ◽  
Electron Backscattered Diffraction ◽  
Gamma Titanium Aluminide ◽  
Z Contrast

The hot workability of gamma titanium aluminide alloy, Ti-48Al-2V-2Nb, was assessed in the cast condition through a series of compression tests conducted over a range of temperatures (1000 to 1175 °C) and at the strain rate of 10 S-1. The mechanism of dynamics recrystallization has been investigated from SEM Z-contrast images and from the Electron backscattered diffraction EBSD as well. It has been observed that volume fraction of the recrystallized grains increases with increasing the deformation temperature. The major volume fraction of the recrystallized grains was observed in the shear band which was forming at an angle 45 ̊ with respect to the compression direction. The mechanism of breaking of the laths and the region of the dynamic recrystallization were also investigated from the SEM Z-contrast image and EBSD. The dynamic recrystallization occurred in the region of the broken laths and shear bands. The breaking of the laths was because of the kinking of the lamellae. The shear band, kinked lamellae and dynamic recrystallized region where all investigated simultaneously.

Numerical Simulation and Experimental Verification of Microstructure Evolution during the Seamless Tube Extrusion of Semi-Continuous Casting AZ31 Magnesium Alloy

2017 ◽  
Vol 898 ◽  
pp. 79-85
Author(s):  
Tao Lin ◽  
Ji Xue Zhou ◽  
Bai Chang Ma ◽  
Yun Teng Liu ◽  
Di Zhang ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Magnesium Alloy ◽  
Continuous Casting ◽  
Dynamic Recrystallization ◽  
Volume Fraction ◽  
Seamless Tube ◽  
Compression Tests ◽  
Extrusion Speed ◽  
Tube Extrusion ◽  
Az31 Mg Alloy

Based on the stress-strain curves at the temperature of 300-450 °C with strain rate of 0.01-1 s−1 by hot compression tests, the empirical dynamic recrystallization models for the semi-continuous AZ31magnesium alloy were developed. The dynamic recrystallization evolution during the seamless tube extrusion of the AZ31 Mg alloy was simulated by numerical method with the derived models and validated by experiment measurements. The results show that at certain extrusion speed the influence of the extruding temperature on the dynamic recrystallization fraction was significant. With the increase of the extruding temperature the volume fraction of dynamic recrystallization increase obviously. The predicted dynamic recrystallization fraction was in an excellent agreement with the experimental results.

scholarly journals Study of Static Recrystallization Kinetics and the Evolution of Austenite Grain Size by Dynamic Recrystallization Refinement of an Eutectoid Steel

Metals ◽  
2019 ◽  
Vol 9 (12) ◽  
pp. 1289
Author(s):  
Cesar Facusseh ◽  
Armando Salinas ◽  
Alfredo Flores ◽  
Gerardo Altamirano
Keyword(s):  
Grain Size ◽  
Dynamic Recrystallization ◽  
Static Recrystallization ◽  
Controlled Rolling ◽  
Strain Rates ◽  
Peak Strain ◽  
Compression Tests ◽  
Eutectoid Steel ◽  
Austenite Grain Size ◽  
Austenite Grain

Interrupted and continuous hot compression tests were performed for eutectoid steel over the temperature range of 850 to 1050 °C and while using strain rates of 0.001, 0.01, 0.1, and 1 s−1. The interrupted tests were carried out to characterize the kinetics of static recrystallization(SRX) and determinate the interpass time conditions that are required for initiation and propagation of dynamic recrystallization (DRX), while considering that the material does not contain microalloying elements additions for the recrystallization delay. Continuous testing was used to investigate the evolution of the austenite grain size that results from DRX. The results indicate that carbon content accelerates the SRX rate. This effect was observed when the retardation of recrystallization due to a decrease in deformation temperature from 1050 to 850 °C was only about one order of magnitude. The expected decelerate effect on the SRX rate when the initial grain size increases from 86 to 387 µm was not significant for this material. Although the strain parameter has a strong influence on SRX rate, in contrast to a lesser degree of strain rate, both of the effects are nearly independent of the chemical composition. The calculated maximum interpass times that are compatible with DRCR (Dynamic Recrystallization Controlled Rolling), for relatively low strain rates, suggest that the onset and maintaining of the DRX is possible. However, while using the empirical equations that were developed in the present work to estimate the maximum times for high strain rates, such as those observed in the wire and rod mills, indicate that the DRX start is feasible, but maintaining this mechanism for 5% softening in each pass after peak strain is not possible.

scholarly journals Finite Element Analysis of Dynamic Recrystallization of Casting Slabs during Hot-Core Heavy Reduction Rolling Process

Metals ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 181
Author(s):  
Haijun Li ◽  
Tianxiang Li ◽  
Meina Gong ◽  
Zhaodong Wang ◽  
Guodong Wang
Keyword(s):  
Grain Size ◽  
Dynamic Recrystallization ◽  
Volume Fraction ◽  
Rolling Process ◽  
Reduction Ratio ◽  
Secondary Development ◽  
Innovative Technology ◽  
Element Analysis ◽  
The Core ◽  
Average Grain Size

Hot-core heavy reduction rolling (HHR2) is an innovative technology, where a two-high rolling mill is installed after the solidification end of a strand, which can significantly eliminate the core defects of the slab. The mill exhibits a heavy reduction ratio, which promotes the dynamic recrystallization (DRX) of the slab. This study aims to optimize the parameters of the HHR2 process considering the effect of DRX on microstructure homogeneity. The secondary development of commercial software DEFORM-3D is conducted to calculate the deformation and DRX behavior of HHR2 for different reduction ratios. The parameters of DRX volume fraction and DRX grain size are compared, and finer DRX grains are obtained when the greater reduction ratios are conducted in HHR2. Then, corresponding to the deformation conditions in the HHR2, the thermal–mechanical simulations are conducted on the Gleeble3800 to obtain the average grain sizes before and after this process. When the reduction amount increases from 20 mm to 50 mm, the difference of average grain size between the core and the surface reduces by 52%. In other words, appropriately enhancing the reduction ratio is helpful to reduce the average austenite grain and promote the microstructure uniformity of the slab. These results provide some valuable information on the design of deformation parameters for HHR2.

High Temperature Deformation Mechanisms and Processing Map for Hot Working of Cast-Homogenized Mg-3Sn-2Ca Alloy

2010 ◽  
Vol 638-642 ◽  
pp. 3616-3621 ◽  
Author(s):  
K.P. Rao ◽  
Y.V.R.K. Prasad ◽  
Norbert Hort ◽  
Karl Ulrich Kainer
Keyword(s):  
Strain Rate ◽  
Processing Map ◽  
Volume Fraction ◽  
Flow Instability ◽  
Back Stress ◽  
Hot Working ◽  
High Temperature Deformation ◽  
Temperature Deformation ◽  
Strain Rates ◽  
Compression Tests

The hot working behavior of Mg-3Sn-2Ca alloy has been investigated in the temperature range 300–500 oC and strain rate range 0.0003–10 s-1, with a view to evaluate the mechanisms and optimum parameters of hot working. For this purpose, a processing map has been developed on the basis of the flow stress data obtained from compression tests. The stress-strain curves exhibited steady state behavior at strain rates lower than 0.01 s-1 and at temperatures higher than 350 oC and flow softening occurred at higher strain rates. The processing map exhibited two dynamic recrystallization domains in the temperature and strain rate ranges: (1) 300–420 oC and 0.0003–0.003 s-1, and (2) 420–500 oC and 0.003–1.0 s-1, the latter one being useful for commercial hot working. Kinetic analysis yielded apparent activation energy values of 161 and 175 kJ/mole in domains (1) and (2) respectively. These values are higher than that for self-diffusion in magnesium suggesting that the large volume fraction of intermetallic particles CaMgSn present in the matrix generates considerable back stress. The processing map reveals a wide regime of flow instability which gets reduced with increase in temperature or decrease in strain rate.

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