Effect of Ultrasonic-Assisted Casting on Hot Deformation Mechanism and Microstructure of 35CrMo Steel Ingot

Hot compression tests were performed with strain rates (0.01–10 s−1) and temperatures (850–1150 °C). The power law relationship between the critical stress and critical strain and Zener–Hollomon parameters was determined by θ-σ curves. Microstructure was investigated by electron backscattered diffraction. The results showed that the flow behavior and microstructure of 35CrMo steel was affected by ultrasonic-assisted casting. The activation energy of non-ultrasonic and ultrasonic-assisted 35CrMo steel were 410 ± 9.9 and 386 ± 9.4 kJ/mol, respectively, and the activation energy of ultrasonic-assisted specimens was reduced by 6%. In addition, the ultrasonic-assisted treatment refines the grains to some extent and makes the softening process of ultrasonic-assisted samples progress faster, which promoted the development of dynamic recrystallization and the production of Σ3 boundaries. The discontinuous dynamic recrystallization was the main DRX nucleation mechanism of the 35CrMo steel.

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Constitutive Equation of Mg-13Al-3Ca-3Zn-1Nd-0.2Mn Magnesium Alloy

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.968.3 ◽

2014 ◽

Vol 968 ◽

pp. 3-6

Author(s):

Wei Chen ◽

Gang Chen ◽

Jing Zhai ◽

Li Ma

Keyword(s):

Activation Energy ◽

Magnesium Alloy ◽

Constitutive Equation ◽

Temperature Regime ◽

Constitutive Equations ◽

Flow Behavior ◽

Strain Rates ◽

Compression Tests ◽

Related Material ◽

Base Analysis

The constitutive equations may properly describe the flow behavior of the materials. In the present study, the constitutive equation of Mg-13Al-3Ca-3Zn-1Nd-0.2Mn alloy were investigated using hot compression tests at the temperatures range of 200, 250, 300, 350 and 400°Cwith the constant strain rates of 0.001, 0.01, 0.1, 1 and 10s-1.The hot working constitutive base analysis has been conducted on the experimental alloy. The related material constants n, α and β, as well as the activation energy Q for each temperature regime have been determined. At last, the constitutive equations is given.

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Deformation Behavior of Mg-7Gd-5Y-1Nd-0.5Zr Alloy during Hot Compression

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.633-634.108 ◽

2014 ◽

Vol 633-634 ◽

pp. 108-115

Author(s):

Ting Li ◽

Kui Zhang ◽

Zhi Wei Du ◽

Jia Wei Yuan ◽

Xing Gang Li

Keyword(s):

Activation Energy ◽

Regression Analysis ◽

Dynamic Recrystallization ◽

Apparent Activation Energy ◽

Deformation Behavior ◽

Optical Microscope ◽

Hot Compression ◽

Avrami Equation ◽

Compression Tests ◽

Electron Backscattered Diffraction

The hot deformation behavior of Mg-7Gd-5Y-1Nd-0.5Zr alloy was investigated by compression tests at temperatures of 673 K, 713 K, 753 K, and 793 K and strain rates of 0.001 s-1, 0.01 s-1, 0.1 s-1, and 1s-1. The stress-strain curves exhibit typical dynamic recrystallization behavior with a single peak stress followed by a gradual fall toward a steady-state stress. The apparent activation energy of deformation and constitutive equations for the alloy were determined through regression analysis for conventional hyperbolic sine equation. The apparent activation energy of DRX and dynamic kinetics model for alloy were determined using the regression analysis for Avrami equation. Optical microscope and electron backscattered diffraction were employed to investigate the microstructure evolution of Mg-7Gd-5Y-1Nd-0.5Zr alloy during hot compression. The results suggested that the grain boundary is the main nucleation sites of dynamic recrystallization, and (0001) basal fiber texture has formed during hot compression.

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Dynamic Recrystallization of the Alloy Fe-40at.%Al-Zr-B

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.592-593.161 ◽

2013 ◽

Vol 592-593 ◽

pp. 161-164

Author(s):

Ivo Schindler ◽

Petr Kawulok ◽

Rostislav Kawulok ◽

Stanislav Rusz

Keyword(s):

Activation Energy ◽

Flow Stress ◽

Dynamic Recrystallization ◽

Maximum Flow ◽

Material Constant ◽

Iron Aluminide ◽

Coarse Grained ◽

Strain Rates ◽

Compression Tests ◽

Hollomon Parameter

On the basis of the uniaxial compression tests realized in the temperature range from 800 °C to 1200 °C and at strain rates from 0.05 s-1 to 30 s-1 the value of the activation energy at hot forming of coarse-grained as-cast iron aluminide Fe40at.%Al-Zr-B was calculated as Q = 502 kJ·mol-1. With use of this material constant, relatively precise mathematical description of the maximum flow stress and the corresponding strain in dependence on the Zener-Hollomon parameter was possible. As was discovered by metallographical analysis, at high values of the Zener-Hollomon parameter slight decrease in flow stress occurs even without significant course of dynamic recrystallization.

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Dynamic Restoration Processes in High-Mn TWIP Steels

Journal of Engineering Materials and Technology ◽

10.1115/1.3120394 ◽

2009 ◽

Vol 131 (4) ◽

Cited By ~ 15

Author(s):

M. Sabet ◽

A. Zarei-Hanzaki ◽

Sh. Khoddam

Keyword(s):

Dynamic Recrystallization ◽

Flow Behavior ◽

Austenitic Steels ◽

Strain Rates ◽

Compression Tests ◽

Steel Microstructure ◽

Different Temperatures ◽

Twip Steels ◽

Equiaxed Grains ◽

Microstructural Studies

The twinning-induced plasticity (TWIP) phenomenon is established as the most effective mechanism to enhance the formability of the advanced high-Mn (15–30 wt %) austenitic steels (known as TWIP steels). As the formability is very sensitive to the steel microstructure, the study of their hot deformation characteristics is highly desired. The aim of the present work is to investigate the effects of strain rate on the high temperature flow behavior, dynamic recrystallization (DRX) and the microstructural evolution of a grade of TWIP steels (with 29 wt % Mn) through single hit compression testing. The hot compression tests were carried out at two different temperatures (850°C and 1150°C) applying a range of strain rates (0.001–0.1 s−1). The results indicated a greater deformation resistance at higher strain rates. The detected broad stress peaks at higher strain rates were related to the occurrence of DRX. The microstructural studies revealed that, in addition to DRX, a geometrical dynamic recrystallization occurred at 850°C. This results in a microstructure with finer equiaxed grains.

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Effect of Trace Magnesium Additions on the Dynamic Recrystallization in Cast Alloy 825 after One-Hit Hot-Deformation

Metals ◽

10.3390/met11010036 ◽

2020 ◽

Vol 11 (1) ◽

pp. 36

Author(s):

Munir Al-Saadi ◽

Wangzhong Mu ◽

Christopher N. Hulme-Smith ◽

Fredrik Sandberg ◽

Pär G. Jönsson

Keyword(s):

Service Life ◽

Dynamic Recrystallization ◽

Hot Deformation ◽

Cast Alloy ◽

True Strain ◽

Peak Strain ◽

Compression Tests ◽

Electron Backscattered Diffraction ◽

Hollomon Parameter ◽

Test Conditions

Alloy 825 is widely used in several industries, but its useful service life is limited by both mechanical properties and corrosion resistance. The current work explores the effect of the addition of magnesium on the recrystallization and mechanical behavior of alloy 825 under hot compression. Compression tests were performed under conditions representative of typical forming processes: temperatures between 1100 and 1250 °C and at strain rates of 0.1–10 s−1 to a true strain of 0.7. Microstructural evolution was characterized by electron backscattered diffraction. Dynamic recrystallization was found to be more prevalent under all test conditions in samples containing magnesium, but not in all cases of conventional alloy 825. The texture direction ⟨101⟩ was the dominant orientation parallel to the longitudinal direction of casting (also the direction in which the samples were compressed) in samples that contained magnesium under all test conditions, but not in any sample that did not contain magnesium. For all deformation conditions, the peak stress was approximately 10% lower in material with the addition of magnesium. Furthermore, the differences in the peak strain between different temperatures are approximately 85% smaller if magnesium is present. The average activation energy for hot deformation was calculated to be 430 kJ mol−1 with the addition of magnesium and 450 kJ mol−1 without magnesium. The average size of dynamically recrystallized grains in both alloys showed a power law relation with the Zener–Hollomon parameter, DD~Z−n, and the exponent of value, n, is found to be 0.12. These results can be used to design optimized compositions and thermomechanical treatments of alloy 825 to maximize the useful service life under current service conditions. No experiments were conducted to investigate the effects of such changes on the service life and such experiments should now be performed.

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Constitutive Equation for 3104 Alloy at High Temperatures in Consideration of Strain

High Temperature Materials and Processes ◽

10.1515/htmp-2014-0238 ◽

2016 ◽

Vol 35 (6) ◽

pp. 599-605 ◽

Cited By ~ 1

Author(s):

Fuqiang Zhen ◽

Jianlin Sun ◽

Jian Li

Keyword(s):

Hot Deformation ◽

Flow Behavior ◽

Temperature Correction ◽

Strain Rates ◽

Compression Tests ◽

Hot Deformation Behavior ◽

Element Analysis ◽

Hollomon Parameter ◽

The Finite Element Analysis ◽

Effects Of Temperature

AbstractThe flow behavior of 3104 aluminum alloy was investigated at temperatures ranging from 250°C to 500°C, and strain rates from 0.01 to 10 s−1 by isothermal compression tests. The true stress–strain curves were obtained from the measured load–stroke data and then modified by friction and temperature correction. The effects of temperature and strain rate on hot deformation behavior were represented by Zener–Hollomon parameter including Arrhenius term. Additionally, the influence of strain was incorporated considering the effect of strain on material constants. The derived constitution equation was applied to the finite element analysis of hot compression. The results show that the simulated force is consistent with the measured one. Consequently, the developed constitution equation is valid and feasible for numerical simulation in hot deformation process of 3104 alloy.

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Hot Deformation Behavior of a Ni-Based Superalloy with Suppressed Precipitation

Metals ◽

10.3390/met11040605 ◽

2021 ◽

Vol 11 (4) ◽

pp. 605

Author(s):

Franco Lizzi ◽

Kashyap Pradeep ◽

Aleksandar Stanojevic ◽

Silvana Sommadossi ◽

Maria Cecilia Poletti

Keyword(s):

Dynamic Recrystallization ◽

Strain Rate ◽

Hot Deformation ◽

Strain Rates ◽

Compression Tests ◽

Deformation Bands ◽

Stress Softening ◽

Relative Stress ◽

The Matrix ◽

Thermomechanical Processes

Inconel®718 is a well-known nickel-based super-alloy used for high-temperature applications after thermomechanical processes followed by heat treatments. This work describes the evolution of the microstructure and the stresses during hot deformation of a prototype alloy named IN718WP produced by powder metallurgy with similar chemical composition to the matrix of Inconel®718. Compression tests were performed by the thermomechanical simulator Gleeble®3800 in a temperature range from 900 to 1025 °C, and strain rates scaled from 0.001 to 10 s−1. Flow curves of IN718WP showed similar features to those of Inconel®718. The relative stress softening of the IN718WP was comparable to standard alloy Inconel®718 for the highest strain rates. Large stress softening at low strain rates may be related to two phenomena: the fast recrystallization rate, and the coarsening of micropores driven by diffusion. Dynamic recrystallization grade and grain size were quantified using metallography. The recrystallization grade increased as the strain rate decreased, although showed less dependency on the temperature. Dynamic recrystallization occurred after the formation of deformation bands at strain rates above 0.1 s−1 and after the formation of subgrains when deforming at low strain rates. Recrystallized grains had a large number of sigma 3 boundaries, and their percentage increased with strain rate and temperature. The calculated apparent activation energy and strain rate exponent value were similar to those found for Inconel®718 when deforming above the solvus temperature.

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Hot Deformation and Dynamic Recrystallization in Titanium Aluminide

Materials Science Forum ◽

10.4028/www.scientific.net/msf.941.1391 ◽

2018 ◽

Vol 941 ◽

pp. 1391-1396 ◽

Cited By ~ 5

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.

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A Comparative Study on Johnson Cook, Modified Zerilli–Armstrong, and Arrhenius-Type Constitutive Models to Predict Compression Flow Behavior of SnSbCu Alloy

Materials ◽

10.3390/ma12101726 ◽

2019 ◽

Vol 12 (10) ◽

pp. 1726 ◽

Cited By ~ 5

Author(s):

Tongyang Li ◽

Bin Zhao ◽

Xiqun Lu ◽

Hanzhang Xu ◽

Dequan Zou

Keyword(s):

Experimental Data ◽

Flow Behavior ◽

Constitutive Models ◽

Strain Range ◽

Type Model ◽

Strain Rates ◽

Compression Tests ◽

Predictive Values ◽

Specific Strain ◽

Optimum Model

The flow behavior of the SnSbCu alloy is studied experimentally by the compression tests in the range of the strain rates from 0.0001 to 0.1 s−1 and temperature from 293 to 413 K. Based on the experimental data, three constitutive models including the Johnson–Cook (J–C), modified Zerilli–Armstrong (Z–A), and Arrhenius-type (A-type) models are compared to find out an optimum model to describe the flow behavior of the SnSbCu alloy. The results show that the J–C model could predict the flow behavior of the SnSbCu alloy accurately only at some specific strain rates and temperature near the reference values. The modified Z–A and A-type constitutive models can give better fitting results than the J–C model. While, at high strains, the predictive values of the modified Z–A model have larger errors than those at low strains, which means this model has limitations at high strains. By comparison, the A-type model could predict the experimental results accurately at the whole strain range, which indicates that it is a more suitable choice to describe the flow behavior of the SnSbCu alloy in the focused range of strain rates and temperatures. The work is beneficial to solve the tribological problem of the bearing of the marine engine by integrating the accurate constitutive model into the corresponding numerical model.

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

Metals ◽

10.3390/met9121289 ◽

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.

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