Microstructure Mapping: An Approach to Quantitative Interpretation of Microstructural Evolution in Indian Fast Reactor Advanced Clad Material during Hot Forging

2015 ◽  
Vol 830-831 ◽  
pp. 350-353 ◽  
Author(s):  
B. Aashranth ◽  
Santosh Kumar ◽  
Dipti Samantaray ◽  
Shaju K. Albert ◽  
Utpal Borah ◽  
...  
Keyword(s):  
Microstructural Evolution ◽  
Fast Reactor ◽  
True Strain ◽  
Hot Forging ◽  
Strain Rate Range ◽  
Mechanical Processing ◽  
True Strain Rate ◽  
Strain Data ◽  
Instability Map ◽  
Map Analysis

In this paper, microstructural evolution of Indian Fast Reactor Advanced Clad (IFAC-1) steel during thermo-mechanical processing has been investigated. Hot isothermal forging has been simulated in a Gleeble® thermo-mechanical simulator in the temperature range 1173-1473K and true strain rate range 0.01-100s-1. Instability map has been developed using the stress-strain data obtained. Effect of major forging parameters on various microstructural features has been studied quantitatively. Results from this study have been used to construct various maps (‘μ-maps’) representing different aspects of microstructural evolution. An analogy between the μ-maps and instability maps provides essential insights into possible instability mechanisms operative in the material. The μ-map analysis shows potential as a tool for optimisation of industrial-scale forging parameters.

On the High Temperature Creep and Relaxation Behaviour of Zr-based Bulk Metallic Glasses

2000 ◽  
Vol 644 ◽  
Author(s):  
B. S. S. Daniel ◽  
M. Heilmaier ◽  
A. Reger-Leonhard ◽  
J. Eckert ◽  
L. Schultz
Keyword(s):  
High Temperature ◽  
Strain Rate ◽  
Deformation Behaviour ◽  
True Strain ◽  
Constant Load ◽  
Strain Rate Range ◽  
High Temperature Deformation ◽  
Temperature Deformation ◽  
Creep Tests ◽  
True Strain Rate

AbstractCreep tests under constant load as well as constant true strain rate were carried out at near the glass transition temperatures (Tg) to study the time dependent flow behaviour of a Zr-based bulk metallic glass (BMG). The strain rate - stress relation over a wide strain rate-range (10-7 to 10-2 s-1) was established for different temperatures. The high temperature deformation behaviour is explained on the basis of stress induced creation of free volume versus diffusion controlled annihilation processes. It was found that the creep kinetics near Tg is controlled by the mobility of atoms with an activation energy value Q =410kJ/mol.

scholarly journals Effects of deformation on the microstructure of a Ti-V microalloyed steel in the phase transition region

2004 ◽  
Vol 57 (4) ◽  
pp. 303-311
Author(s):  
Wiliam Regone ◽  
Sérgio Tonini Button
Keyword(s):  
Phase Transition ◽  
Phase Transformation ◽  
Transition Region ◽  
Microstructural Evolution ◽  
Microalloyed Steel ◽  
Hot Forging ◽  
Microalloyed Steels ◽  
Air Cooling ◽  
Water Cooling ◽  
Phase Transition Region

Microalloyed steels are used in the forging of many automotive parts like crankshafts and connecting rods. They are hot worked in a sequence of stages that includes the heating to the soaking temperature, followed by forging steps, and finally the controlled cooling to define the microstructure and mechanical properties. In this work it was investigated the thermomechanical behavior and the microstructural evolution of a Ti-V microalloyed steel in the phase transition region. Torsion tests were done with multiple steps with true strain equal to 0.26 in each step. After each torsion step the samples were continuous cooled for 15 seconds to simulate hot forging conditions. These tests provided results for the temperature at the beginning of the phase transformation, and allowed to analyze the microstructural changes. Also, workability tests were held to analyze the microstructural evolution by optical and scanning electron microscopy. Results from the torsion tests showed that the temperature for the beginning of phase transformation is about 700 ºC. Workability tests held at 700 ºC followed by water-cooling presented microstructures with different regions: strain hardened, and static and dynamic recrystallized. Workability tests at 700 ºC followed by air-cooling showed a complex microstructure with ferrite, bainite and martensite, while tests at 650 and 600 ºC followed by water-cooling showed a microstructure with allotriomorphic ferrite present in the grain boundaries of the previous austenite.

scholarly journals Study on the Hot Deformation Characterization of Borated Stainless Steel by Hot Isostatic Pressing

Materials ◽  
2021 ◽  
Vol 14 (23) ◽  
pp. 7110
Author(s):  
Yanbin Pei ◽  
Xuanhui Qu ◽  
Qilu Ge ◽  
Tiejun Wang
Keyword(s):  
Stainless Steel ◽  
Hot Deformation ◽  
True Strain ◽  
Hot Isostatic Pressing ◽  
Microstructural Analysis ◽  
Critical Conditions ◽  
True Strain Rate ◽  
Isostatic Pressing ◽  
Different Temperatures ◽  
Borated Stainless Steel

Borated stainless steel (BSS) specimens have a boron content of 1.86 wt%, and are prepared by hot isostatic pressing (HIP) conducted at different temperatures, ranging from 1000 to 1100 °C and a constant true strain rate (0.01, 0.1, 1 and 10 s−1). These tests, with observations and microstructural analysis, have achieved the hot deformation characteristics and mechanisms of BSS. In this research, the activation energy (Q) and Zener–Hollomon parameter (Z) were contrasted against the flow curves: Q = 442.35 kJ/mol. The critical conditions associated with the initiation of dynamic recrystallization (DRX) for BSS were precisely calculated based on the function between the strain hardening rate with the flow stress: at different temperatures from 1000 to 1100 °C: the critical stresses were 146.69–254.77 MPa and the critical strains were 0.022–0.044. The facts show that the boron-containing phase of BSS prevented the onset of DRX, despite the saturated boron in the austenite initiated DRX. The microstructural analysis showed that hot deformation promoted the generation of borides, which differed from the initial microstructure of HIP. The inhomogeneous distribution of elements in the boron-containing phase was caused by hot compression.

scholarly journals Hot Deformation Treatment of Grain-Modified Mg–Li Alloy

Materials ◽  
2020 ◽  
Vol 13 (20) ◽  
pp. 4557
Author(s):  
Mariusz Król ◽  
Przemysław Snopiński ◽  
Marek Pagáč ◽  
Jiří Hajnyš ◽  
Jana Petrů
Keyword(s):  
Hot Deformation ◽  
Cast Alloy ◽  
Material Model ◽  
Strain Rate Range ◽  
Al Alloy ◽  
Grain Refiner ◽  
Systematic Analysis ◽  
Dynamic Material Model ◽  
Instability Map

In this work, a systematic analysis of the hot deformation mechanism and a microstructure characterization of an as-cast single α-phase Mg–4.5 Li–1.5 Al alloy modified with 0.2% TiB addition, as a grain refiner, is presented. The optimized constitutive model and hot working terms of the Mg–Li alloy were also determined. The hot compression procedure of the Mg–4.5 Li–1.5 Al + 0.2 TiB alloy was performed using a DIL 805 A/D dilatometer at deformation temperatures from 250 °C to 400 °C and with strain rates of 0.01–1 s−1. The processing map adapted from a dynamic material model (DMM) of the as-cast alloy was developed through the superposition of the established instability map and power dissipation map. By considering the processing maps and microstructure characteristics, the processing window for the Mg–Li alloy were determined to be at the deformation temperature of 590 K–670 K and with a strain rate range of 0.01–0.02 s−1.

scholarly journals Effect of Strain Rate on Hot Ductility of a Duplex Stainless Steel

2019 ◽  
Vol 2019 ◽  
pp. 1-6 ◽  
Author(s):  
Zhenhua Wang ◽  
Wenyuan Ma ◽  
Chengming Wang
Keyword(s):  
Strain Rate ◽  
Hot Forging ◽  
Total Elongation ◽  
Strain Rate Range ◽  
Hot Ductility ◽  
Hot Workability ◽  
Crack Tips ◽  
The Difference ◽  
Edge Cracking ◽  
Reduction In Area

Duplex stainless steels (DSSs) often have bad hot workability. In this study, specimens of 2205 DSS were hot tensioned over a strain rate range from 0.005 s–1 to 50 s–1 to examine the hot ductility. The crack morphology was observed, and the dependence of hot ductility on the strain rate was analyzed. From 0.005 s–1 to 0.5 s–1, both the total elongation and the reduction in area increased with the strain rate. The reduction in area exhibited a small decrease when the strain rate was greater than 0.5 s–1. More than 85% of cracks formed between the ferrite and austenite, and no less than 70% of crack tips propagated between the ferrite and austenite. When the strain rate was increased from 0.005 s–1 to 0.5 s–1, dynamic recrystallization was promoted in the austenite, and the number fraction of low-angle grain boundaries in the ferrite was improved. The higher strain rate reduced the difference between ferrite and austenite in hardness, which improved the hot ductility. For 2205 DDS, the suggested strain rate is 0.5 s–1 and above to avoid surface and edge cracking during hot forging or hot rolling. The findings will be of value for the understanding of hot ductility of DSSs and other dual-phase alloys.

A Mathematical Description for the Stress-Strain Behavior of Annealed 2 1/4 Cr-1 Mo Steel

1976 ◽  
Vol 98 (2) ◽  
pp. 118-125 ◽  
Author(s):  
R. L. Klueh ◽  
T. L. Hebble
Keyword(s):  
Mathematical Description ◽  
Flow Behavior ◽  
True Strain ◽  
Empirical Relationship ◽  
Tensile Tests ◽  
Strain Rates ◽  
Strain Behavior ◽  
Test Conditions ◽  
Wide Range ◽  
Strain Data

We have conducted a detailed series of tensile tests on one heat of annealed 2 1/4 Cr-1 Mo steel over the range 25 to 593°C (75 to 1100°F) and at nominal strain rates of 0.4, 0.04, 0.004, and 0.0004/min. To determine an empirical relationship to represent the flow behavior, we fitted the true-stress true-strain data from these tests to several proposed models. The models fit were those proposed by Hollomon, Ludwik, Ludwigson, and Voce. From a comparison of the standard error of estimate, the Voce equation was concluded to be the best mathematical description of the data under most test conditions and the best single representation over the wide range of test conditions.

Microstructural Evolution of Two Medium Carbon Microalloyed Steels during Hot Forging Process

2005 ◽  
Vol 500-501 ◽  
pp. 155-162 ◽  
Author(s):  
A. Al Omar ◽  
A. Chenaoui ◽  
Rachid Dkiouak ◽  
Jose María Cabrera ◽  
Jose Manuel Prado
Keyword(s):  
Microstructural Evolution ◽  
Hot Forging ◽  
Microalloyed Steels ◽  
Hollomon Parameter ◽  
Medium Carbon ◽  
Grain Sizes ◽  
Recrystallized Grain Size ◽  
Carbon Microalloyed ◽  
Hot Forging Process ◽  
Cyclic Dynamic

The main aim of the present investigation was to study the flow behaviour of two medium carbon microalloyed steels under hot forming conditions, and to analyse its microstructural evolution. The dependence of recrystallized grain size (Drec) on the Zener-Hollomon parameter Z shows a bimodal behaviour with transition from single to cyclic dynamic recrystallization. Also we observed that the variation of Drec normalized by Burgers vector (b) with sss normalized by shear modulus ( µ) shows the same bimodal behaviour cited above. The Derby’s universal equation cited in literature for recrystallized grain sizes was not followed; it seems that the presence of fine precipitated particles has a clear effect on this disagreement.

scholarly journals Hot Deformation Behaviors of the Mg-3Sn-2Al-1Zn Alloy: Investigation on its Constitutive Equation, Processing Map, and Microstructure

Materials ◽  
2020 ◽  
Vol 13 (2) ◽  
pp. 312 ◽  
Author(s):  
Yuhang Guo ◽  
Yaodong Xuanyuan ◽  
Xuannam Ly ◽  
Sen Yang
Keyword(s):  
Constitutive Equation ◽  
Strain Rate ◽  
Processing Map ◽  
True Strain ◽  
Strain Rate Range ◽  
Hot Working ◽  
Microstructure Observation ◽  
Stability And Instability ◽  
Deformation Behaviors ◽  
Working Parameters

In this work, the Mg-3Sn-2Al-1Zn (TAZ321, wt. %) alloy with excellent high temperature resistance was compressed using a Gleeble-3500 thermo-mechanical simulator at a wide temperature and the strain rate range. The kinetics analyses showed that the dominant deformation mechanism was likely caused by the cross slipping of dislocations. A constitutive equation which expressed the relationship between the flow stress, deformation temperature, and strain rate was established, and the average activation energy Q was calculated to be 172.1 kJ/mol. In order to delineate the stability and instability working domains, as well as obtain the optimum hot working parameters of the alloy, the hot processing maps in accordance with Prassad’s criterion are constructed at the true strain of 0.2, 0.4, 0.6, and 0.8, respectively. Based on the hot processing map and microstructure observation, the optimum hot working parameter was determined to be 350 °C/1 s−1. The continuous fine dynamic recrystallization (CDRX) grains occurred in the optimum deformation zone. The predicted instability domains was identified as T = 200–300 °C, ε ˙ = 10−2–1 s−1, which corresponded to the microstructure of deformation twinning and micro cracks at the intersection of grain boundaries.

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