Hot Deformation and Microstructural Characteristics of Nitrogen Enhanced 316L Stainless Steel

2016 ◽  
Vol 716 ◽  
pp. 317-322 ◽  
Author(s):  
Santosh Kumar ◽  
B. Aashranth ◽  
Dipti Samantaray ◽  
Marimuthu Arvinth Davinci ◽  
Utpal Borah ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Critical Strain ◽  
316L Stainless Steel ◽  
Peak Stress ◽  
Strain Rate Range ◽  
Isothermal Compression ◽  
Compression Tests ◽  
Microstructural Characteristics ◽  
Analysis Of Results ◽  
Experimental Data Analysis

Dynamic recrystallization (DRX) in 316LN austenitic stainless steel with 0.14wt% nitrogen has been studied using hot isothermal compression tests carried out in temperature range 1073-1423K and strain rate range 0.001 - 10 s-1. Critical strain and stress for DRX has been characterized using experimental data. Analysis of results shows that for the entire domain the critical stress is directly proportional to peak stress. However, no clear relationship between εc and εp prevails over the entire tested domain. Dynamic Recrystallized (DRX) grains are quantified by GOS and KAM maps. The four stages of DRX progression have been identified using the correlation between GOS and critical strain at different deformation conditions.

Critical Strain for the Initiation of Dynamic Recrystallization in a Ni-Fe Base Alloy

2004 ◽  
Vol 449-452 ◽  
pp. 577-580
Author(s):  
Young Sang Na ◽  
Young Mok Rhyim ◽  
J.Y. Lee ◽  
Jae Ho Lee
Keyword(s):  
Dynamic Recrystallization ◽  
Strain Rate ◽  
Critical Strain ◽  
Base Alloy ◽  
Strain Rate Range ◽  
Boundary Phase ◽  
Alloy 718 ◽  
Compression Tests ◽  
Temperature Range ◽  
Critical Strains

In order to quantitatively analyze the critical strain for the initiation of dynamic recrystallization in Ni-Fe-based Alloy 718, a series of uniaxial compression tests was conducted in the temperature range 927°C - 1066°C and the strain rate range 5 x 10-4s-1- 5 s-1with varying initial grain size. The critical strains were graphically determined based on one parameter approach and microscopically confirmed. The effect of γ'' (matrix-hardening phase) and δ (grain boundary phase)on the critical strain was simply discussed. The constitutive model for the critical strain of Alloy 718 was constructed using the experimental data obtained from the higher strain rate and the temperature range between 940°C and 1040°C.

Characterization of Hot Deformation Behavior of Udimet720Li Superalloy Using Processing Map

2014 ◽  
Vol 887-888 ◽  
pp. 1161-1168
Author(s):  
Jian Guo Wang ◽  
Dong Liu ◽  
Tao Wang ◽  
Yan Hui Yang
Keyword(s):  
Strain Rate ◽  
Deformation Behavior ◽  
High Strain ◽  
Flow Behavior ◽  
Strain Range ◽  
Peak Stress ◽  
Strain Rate Range ◽  
Hot Working ◽  
Compression Tests ◽  
Hollomon Parameter

The deformation behavior of a Udimet720Li superalloy under hot compression tests was characterized in the temperature range of 1060~1160°C and strain rate range of 0.001~20s-1. Processing maps were conducted at a series of strains to calculate the efficiency of hot working and to recognize the instability regions of the flow behavior. A Zener-Hollomon parameter is given to characterize the dependence of peak stress on temperature and strain rate. The efficiency of power dissipation of the Udimet720Li superalloy obtained in a strain range of 0.1~0.7 are essentially similar, which indicates that strain does not have a significant influence and the instability region shown in high strain and high strain rates at all temperatures. The regions for the full recrystallization can be divided by the dissolution beginning temperature of primary γ'which are the optimum hot working parameters.

Work Hardening and Flow Softening of γ-TiAl Containing Ni

2004 ◽  
Vol 449-452 ◽  
pp. 833-836 ◽  
Author(s):  
Jian Hui Zhang ◽  
Kenong Xia ◽  
Erik Strom ◽  
Zeng Yong Zhong ◽  
Chang Hai Li
Keyword(s):  
Work Hardening ◽  
Flow Behavior ◽  
Peak Stress ◽  
True Stress ◽  
Flow Softening ◽  
Strain Rates ◽  
Isothermal Compression ◽  
Compression Tests ◽  
Steady State Flow ◽  
Ni Addition

This paper presents the true stress - strain curves and data analyses of a Ni-containing TiAl and its reference alloy based on the isothermal compression tests at 1000°C and 0.01 - 1.0s-1strain rates. The results show that the minor Ni addition makes the flow softening coming sooner and therefore significantly lowers the peak stress. Those effects, in addition with a better balance between the work hardening and flow softening during hot deformation, improve the steady state flow behavior of TiAl. The Ni-influence mechanisms are also suggested based on the TEM observation of dislocation configurations and lamellar breakdown during the deformation.

The Strain Dependence of Post-Deformation Softening during the Hot Compression of 304H Stainless Steel

2007 ◽  
Vol 539-543 ◽  
pp. 100-107 ◽  
Author(s):  
John J. Jonas ◽  
Evgueni I. Poliak ◽  
Abbas Najafizadeh
Keyword(s):  
Stainless Steel ◽  
Strain Rate ◽  
Critical Strain ◽  
Test Method ◽  
Peak Strain ◽  
Compression Tests ◽  
Strain Dependence ◽  
Fractional Softening ◽  
Temperature Time ◽  
Strain Dependent

Experiments were carried out in which the dependence of the fractional softening on temperature, time and strain rate was determined in a 304H stainless steel. Three prestrain ranges were identified pertaining to three different post-deformation softening behaviors: 1) prestraining to below the DRX critical strain: strongly strain dependent softening by SRX alone with softening kinetics controlled by growth rate of the nuclei; 2) prestraining to above the DRX critical strain: SRX + MDRX softening with weaker strain dependence of the kinetics but still controlled by grain growth; 3) at a prestrain of ε* and beyond: nucleation-controlled MDRX softening with the full inhibition of SRX. The transition prestrain ε* can exceed the peak strain if the DRX grain refinement ratio g = D0/DDRX > 4. The transition to MDRX-dominated softening can be attributed to a constant value of the normalized strain hardening rate independent of the preloading temperature and strain rate. The softening data from the compression tests show that at ε*, the time for half softening t50 exhibits a minimum. These data differ somewhat from observations obtained in the torsion testing of solid bars, in which no strain dependence of t50 was detected at ε* and beyond. Whether or not the strain dependence of t50 vanishes in the MDRX range is sensitive to the test method employed to study the post-deformation softening.

Constitutive Equation of 5Cr21Mn9Ni4N Valve Steel during Hot Compression

2013 ◽  
Vol 750-752 ◽  
pp. 2165-2169 ◽  
Author(s):  
Yong Qi Cheng ◽  
Zheng Rong Zhang ◽  
Miao Yan Zheng ◽  
Dong Qiang Mo
Keyword(s):  
Flow Stress ◽  
Constitutive Equation ◽  
Strain Rate ◽  
Constitutive Equations ◽  
Peak Stress ◽  
Strain Rate Range ◽  
Hot Compression ◽  
Compression Tests ◽  
State Regime ◽  
Valve Steel

The hot compression tests on a Gleeble-1500D thermal mechanics simulator were carried out under the strain rate range of 1~ 0.005s-1 at the temperature range of 873-1373K in order to evaluate the constitutive equation of 5Cr21Mn9Ni4N valve steel. All of the flow stress curves exhibit a single peak stress, after which the stress is followed by a steady state regime. The results indicate that the deforming behavior is strongly depending on the strain rate and the deforming temperature. According the experimental data, the hyperbolic law is used to develop the constitutive equations. In the constitutive equations, the effect of the deforming temperature and the strain rate are represented by the Zener-Hollomam parameter. And the flow stress curves are coinciding with the constitutive equation of .

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