Effect of Number of Roughing Passes on the Dynamic Transformation of Austenite during Simulated Plate Rolling

2018 ◽  
Vol 941 ◽  
pp. 717-722
Author(s):  
Samuel F. Rodrigues ◽  
Fulvio Siciliano ◽  
Clodualdo Aranas Jr. ◽  
Gedeon S. Reis ◽  
Brian J. Allen ◽  
...  
Keyword(s):  
Grain Size ◽  
Volume Fraction ◽  
Austenite Phase ◽  
Mean Flow ◽  
Grain Sizes ◽  
Dynamic Transformation ◽  
Plate Rolling ◽  
Forward Transformation ◽  
The Mean ◽  
Rough Rolling

When austenite is deformed within the austenite phase field, it partially transforms dynamically into ferrite. Here, plate rolling simulations were carried out on an X70 steel using rough rolling passes of 0.4 strain each. The influence of the number of roughing passes on the grain size and volume fraction of induced ferrite was determined. Up to three roughing passes applied at 1100 °C followed by 5 finishing passes at 900 °C were employed. The sample microstructures were analysed by means of metallographic techniques. Both the critical strain to the onset of dynamic transformation as well as the grain size decreased with pass number during the roughing simulations. For the finishing passes, the mean flow stresses (MFS`s) applicable to each schedule decreased when a higher number of roughing passes was applied. The volume fraction of dynamically formed ferrite retained after simulated rolling increased with the roughing pass number. This is ascribed to the increased amount of ferrite retransformed into austenite and the finer grain sizes produced during roughing. The forward transformation is considered to occur displacively while the retransformation into austenite during holding takes place by a diffusional mechanism. This indicates that both dynamic transformation (DT) and dynamic recrystallization were taking place during straining.

scholarly journals Strain-Induced Ferrite Formation During Steckel Mill Simulations with Varying Roughing Pass Schedules

Metals ◽  
2019 ◽  
Vol 9 (8) ◽  
pp. 814 ◽  
Author(s):  
Henry B. Palhano ◽  
Clodualdo Aranas ◽  
Samuel F. Rodrigues ◽  
Eden S. Silva ◽  
Gedeon S. Reis ◽  
...  
Keyword(s):  
Volume Fraction ◽  
Rolling Process ◽  
Mean Flow ◽  
Dynamic Transformation ◽  
Plate Rolling ◽  
Mean Flow Stress ◽  
The Mean ◽  
Critical Strains ◽  
Microstructure Of The Material ◽  
Very High

It has been previously demonstrated that austenite may undergo partial dynamic transformation (DT) during the plate rolling process. Austenite dynamically transforms into unstable ferrite during hot deformation even at very high temperatures. In this work, the plate rolling simulations, with emphasis on Steckel mill operations, through torsion testing under isothermal conditions were performed on an X70 steel. Four different roughing schedules were tested followed by five finishing passes with pass strains of 0.3 applied at 900 °C. The roughing schedules had zero, one, two and three roughing passes at a temperature of 1100 °C, strain of 0.4 and strain rate of 1 s−1. The stress–strain curves as well as the mean flow stress (MFS) behaviors indicated that both dynamic transformation (DT) and dynamic recrystallization (DRX) occurred during straining. The critical strains for the onset of DT and DRX were determined by means of the double differentiation method and the critical strain values decreased with the number of roughing and finishing strains from the first going to the last pass. It was observed that the volume fraction of the dynamically formed ferrite increased sharply during the finishing stage as the number of previous roughing passes increased, which can be attributed to higher strain accumulation. The results presented here indicate that improved models are needed to control the microstructure of the material during subsequent cooling.

Induced ferrite formation above the Ae3 during plate rolling simulation of a X70 steel

MRS Advances ◽  
2019 ◽  
Vol 4 (57-58) ◽  
pp. 3077-3085
Author(s):  
Samuel F. Rodrigues ◽  
Thiago B. Carneiro ◽  
Clodualdo Aranas ◽  
Eden S. Silva ◽  
Fulvio Siciliano ◽  
...  
Keyword(s):  
Volume Fraction ◽  
Accelerated Cooling ◽  
Strain Accumulation ◽  
Mean Flow ◽  
Ferrite Formation ◽  
Dynamic Transformation ◽  
Cooling Conditions ◽  
Plate Rolling ◽  
Stable Austenite ◽  
The Mean

ABSTRACTPartial amount of austenite can be dynamically transformed into ferrite above the Ae3 temperature when it is being deformed. This happens by a displacive mechanism. On removal of the load, it retransforms back into the stable austenite by diffusional processes. Plate rolling simulation under continuous cooling conditions was carried out on a high Nb X70 steel. Pass strains of 0.2 together with interpass times of 10, 20 and 30 s were employed. The initial and final temperatures for the finishing simulation were 920 and 830 °C, respectively. The mean flow stresses (MFS`s) behaviour indicates that dynamic transformation (DT) and recrystallization (DRX) were taking place during straining. It is shown that ferrite is formed during the roughing passes and increases its volume fraction throughout the finishing rolling steps. The ferrite formation is favoured by strain accumulation, shorter time between passes and also when the temperature reaches the Ae3 line. The results obtained here can be used to design improved models for transformation on accelerated cooling.

Evaluation of Static Liquefaction Characteristics of Saturated Loose Sand Through the Mean Grain Size and Extreme Grain Sizes

2017 ◽  
Vol 35 (5) ◽  
pp. 2079-2105 ◽  
Author(s):  
Leila Hazout ◽  
Zein El-Abidine Zitouni ◽  
Mostefa Belkhatir ◽  
Tom Schanz
Keyword(s):  
Grain Size ◽  
Loose Sand ◽  
Grain Sizes ◽  
Static Liquefaction ◽  
Mean Grain Size ◽  
The Mean

scholarly journals Mathematical Modeling of the Mean Flow Stress, Fractional Softening and Grain Size during the Hot Strip Rolling of C-Mn Steels.

1996 ◽  
Vol 36 (12) ◽  
pp. 1500-1506 ◽  
Author(s):  
F. Siciliano, Jr. ◽  
K. Minami ◽  
T. M. Maccagno ◽  
J. J. Jonas
Keyword(s):  
Mathematical Modeling ◽  
Grain Size ◽  
Flow Stress ◽  
Mean Flow ◽  
Hot Strip Rolling ◽  
Strip Rolling ◽  
Hot Strip ◽  
Mean Flow Stress ◽  
Fractional Softening ◽  
The Mean

Nonlinear vorticity-banding instability in granular plane Couette flow: higher-order Landau coefficients, bistability and the bifurcation scenario

2013 ◽  
Vol 718 ◽  
pp. 131-180 ◽  
Author(s):  
Priyanka Shukla ◽  
Meheboob Alam
Keyword(s):  
Couette Flow ◽  
Volume Fraction ◽  
Critical Density ◽  
Higher Order ◽  
Jump Discontinuity ◽  
Linear Growth Rate ◽  
Plane Couette Flow ◽  
Mean Flow ◽  
Dense Flows ◽  
The Mean

AbstractThe rapid granular plane Couette flow is known to be unstable to pure spanwise perturbations (i.e. perturbations having variations only along the mean vorticity direction) below some critical density (volume fraction of particles), resulting in the banding of particles along the mean vorticity direction: this is dubbed ‘vorticity banding’ instability. The nonlinear state of this instability is analysed using quintic-order Landau equation that has been derived from the pertinent hydrodynamic equations of rapid granular fluid. We have found analytical solutions for related modal/harmonic equations of finite-size perturbations up to quintic order in perturbation amplitude, leading to an exact calculation of both first and second Landau coefficients. This helped to identify the bistable nature of nonlinear vorticity-banding instability for a range of densities spanning from moderately dense to dense flows. For perturbations with small spanwise wavenumbers, the bifurcation scenario for vorticity banding unfolds, with increasing density from the dilute limit, as supercritical pitchfork $\rightarrow $ subcritical pitchfork $\rightarrow $ subcritical Hopf bifurcations. The transition from supercritical to subcritical pitchfork bifurcations is found to occur via the appearance of a degenerate/bicritical point (at which both the linear growth rate and the first Landau coefficient are simultaneously zero) that divides the critical line into two parts: one representing the first-order and the other the second-order phase transitions. Both subcritical oscillatory and stationary solutions have also been uncovered for dilute and dense flows, respectively, when the spanwise wavenumber is large. In all cases, the nonlinear solutions correspond to inhomogeneous states of shear stress and pressure along the vorticity direction, and hence are analogues of vorticity banding in other complex fluids. The quartic-order mean-flow resonance is evidenced in the parameter space for which the second Landau coefficient undergoes a jump discontinuity of infinite order. The importance of retaining higher-order terms to calculate the second Landau coefficient and their possible effects on the nature of bifurcations are elucidated.

Hall-Petch Relationship in Nano-RuAl Prepared by Mechanical Alloying

2001 ◽  
Vol 676 ◽  
Author(s):  
K. W. Liu ◽  
F. Mücklich ◽  
R. Birringer
Keyword(s):  
Grain Size ◽  
Lower Bound ◽  
Unit Cell Volume ◽  
Size Dependence ◽  
Volume Fraction ◽  
Triple Junctions ◽  
Petch Relationship ◽  
Grain Sizes ◽  
Transition Mechanism ◽  
Coble Creep

ABSTRACTA transition from a normal Hall-Petch relationship to an abnormal one is observed at a grain size of approximately 18.5 nm for nano-RuAl. Several models each representing a controlling factor have been employed to rationalize the transition mechanism. The grain sizes corresponding to the dislocation pile-ups lower bound [2] in grain interior are much smaller than the observed transition grain size and no apparent transition grain size has been derived from the grain size dependence of unit cell volume change [5]. While the grain sizes corresponding to the transition of strain rate according to Coble creep [1] and to the significant triple junction volume fraction [3, 4] (1 %) are well consistent with the observed transition grain size. The overall results indicate that the transition of H-P relationship is dominated by the weakening effect of grain boundaries and triple junctions.

Effect of Grain Size and Residual Strain on the Dynamic Transformation of Austenite under Plate Rolling Conditions

2018 ◽  
Vol 89 (6) ◽  
pp. 1700547 ◽  
Author(s):  
Samuel F. Rodrigues ◽  
Clodualdo Aranas ◽  
Binhan Sun ◽  
Fulvio Siciliano ◽  
Stephen Yue ◽  
...  
Keyword(s):  
Grain Size ◽  
Residual Strain ◽  
Dynamic Transformation ◽  
Plate Rolling

Mass Loading Effects on Turbulence Modulation by Particle Clustering in Dilute and Moderately Dilute Channel Flows

2015 ◽  
Vol 137 (11) ◽  
Author(s):  
Jesse Capecelatro ◽  
Olivier Desjardins
Keyword(s):  
Carrier Phase ◽  
Volume Fraction ◽  
Flow Direction ◽  
Channel Flows ◽  
Wall Region ◽  
Mass Loading ◽  
Mean Flow ◽  
Particle Clustering ◽  
Significant Volume ◽  
The Mean

Wall-bounded particle-laden flows exhibit a variety of interesting phenomena that can greatly impact the underlying carrier-phase turbulence in practical systems. This work aims at investigating the effects of particle clustering on the carrier-phase turbulence in both dilute and moderately dilute channel flows via highly resolved Euler–Lagrange simulations. It is shown that the fluid turbulence departs significantly from the initially fully developed turbulent flow at moderate concentrations. In particular, the gas velocity retains a viscous sublayer at higher values of mass loading, but displays a strongly reduced boundary layer thickness and a flatter velocity profile compared to the dilute case. Furthermore, the flow orientation with respect to gravity is found to significantly impact the multiphase dynamics. Particles showed a preference to be in the near-wall region with significant volume fraction fluctuations when gravity opposed the mean flow direction, while particles accumulated at the channel center with less significant volume fraction fluctuations for flows with gravity aligned with the mean flow direction.

Ordering and Grain Growth Kinetics in CoPt Thin Films

1995 ◽  
Vol 398 ◽  
Author(s):  
R. A. Ristau ◽  
K. Barmak ◽  
D. W. Hess ◽  
K. R. Coffey ◽  
M. A. Parker ◽  
...  
Keyword(s):  
Grain Size ◽  
Size Distribution ◽  
Grain Growth ◽  
Grain Size Distribution ◽  
Volume Fraction ◽  
Domain Size ◽  
Face Centered Cubic ◽  
Temperature Range ◽  
Mean Grain Size ◽  
The Mean

ABSTRACTOrdering and grain growth have been studied in a 10 nm thick CoPt alloy film of equiatomic composition annealed in the temperature range 550–700°C by quantifying ordered domain size, volume fraction ordered, grain size, and grain size distribution. Ordering occurs by nucleation and growth of Ll0 ordered domains, with a mean size of 3 nm at 550°C and 19 nm at 700°C. The volume percent ordered shows a dramatic increase from <y1% to approximately 28% between the two extremes of annealing temperature. The mean grain size of the as-deposited films is 5 nm and the entire film is face-centered cubic. Upon annealing in the temperature range 550–600°C, the mean grain size reaches a stagnation limit of 27 nm and the grain size distribution is log-normal. Grain growth resumes beyond 600°C and the mean grain size reaches as high as 55 nm at 700°C. The increase in the coercivity of the annealed films follows the increase in the ordered fraction more closely than the increase in grain size. The shape of the M-H loop shows evidence of coupling between the magnetically hard (ordered) and soft (disordered) regions.

scholarly journals Effect of Temperature and Texture on Hall–Petch Strengthening by Grain and Annealing Twin Boundaries in the MnFeNi Medium-Entropy Alloy

Metals ◽  
2019 ◽  
Vol 9 (1) ◽  
pp. 84 ◽  
Author(s):  
Mike Schneider ◽  
Felicitas Werner ◽  
Dennis Langenkämper ◽  
Christian Reinhart ◽  
Guillaume Laplanche
Keyword(s):  
Grain Size ◽  
Grain Boundaries ◽  
Dislocation Motion ◽  
Annealing Twin ◽  
Effect Of Temperature ◽  
Compression Tests ◽  
Twin Boundaries ◽  
Grain Sizes ◽  
Crystallite Sizes ◽  
The Mean

Among equiatomic alloys of the Cr-Mn-Fe-Co-Ni system, MnFeNi was shown to exhibit a strong anti-invar behavior but little is known regarding its mechanical properties. The objective of the present study is to investigate Hall–Petch strengthening by grain and annealing twin boundaries in MnFeNi. For this purpose, seven different grain sizes between 17 and 216 µm were produced. Mean grain sizes (excluding annealing twin boundaries) and crystallite sizes (including them) were determined using the linear intercept method. Overall, 25% of the boundaries were found to be annealing twin boundaries regardless of the grain size. In some cases, two twin boundaries can be present in one grain forming an annealing twin, which thickness represents one quarter of the mean grain size. Based on a comparison of the mean twin thickness of different alloys with different stacking fault energy (SFE), we estimated an SFE of 80 ± 20 mJ/m2 for MnFeNi. Compression tests of MnFeNi with different grain sizes were performed between 77 and 873 K and revealed a parallel shift of the Hall–Petch lines with temperature. The interaction between dislocations and boundaries was investigated by scanning transmission electron microscopy (STEM) in a deformed specimen. It was found that a large number of dislocations are piling up against grain boundaries while the pile-ups at annealing twin boundaries contain much fewer dislocations. This indicates that annealing twin boundaries in this alloy are less effective obstacles to dislocation motion than grain boundaries.

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