Hot Deformation Behaviors of as Cast 321 Austenitic Stainless Steel

AISI 321 stainless steel has excellent resistance to intergranular corrosion and is generally used in nuclear power reactor vessels and other components. The as-cast and wrought structures are quite different in hot workability, so physical simulation, electron back-scatter diffraction, and hot processing maps were used to study the mechanical behavior and microstructure evolution of as-cast nuclear grade 321 stainless steel in the temperature range of 900–1200 °C and strain rate range of 0.01–10 s−1. The results showed that the flow curve presented work-hardening characteristics. The activation energy was calculated as 478 kJ/mol. The fraction of dynamic recrystallization (DRX) increased with increasing deformation temperature and decreasing strain rate. DRX grain size decreased with increasing Z value. Combining the hot working map and DRX state map, the suggested hot working window was 1000–1200 °C and 0.01–0.1 s−1. The main form of instability was necklace DRX. The nucleation mechanism of DRX was the migration of subgrains. The δ phase reduced the activation energy and promoted DRX nucleation of the tested steel.

Download Full-text

Hot Workability of 300M Steel Investigated by In Situ and Ex Situ Compression Tests

Metals ◽

10.3390/met9080880 ◽

2019 ◽

Vol 9 (8) ◽

pp. 880 ◽

Cited By ~ 2

Author(s):

Rongchuang Chen ◽

Haifeng Xiao ◽

Min Wang ◽

Jianjun Li

Keyword(s):

Flow Stress ◽

Strain Rate ◽

Hot Working ◽

Ex Situ ◽

Lower Strain Rate ◽

Hot Workability ◽

Compression Tests ◽

300M Steel ◽

Lower Strain

In this work, hot compression experiments of 300M steel were performed at 900–1150 °C and 0.01–10 s−1. The relation of flow stress and microstructure evolution was analyzed. The intriguing finding was that at a lower strain rate (0.01 s−1), the flow stress curves were single-peaked, while at a higher strain rate (10 s−1), no peak occurred. Metallographic observation results revealed the phenomenon was because dynamic recrystallization was more complete at a lower strain rate. In situ compression tests were carried out to compare with the results by ex situ compression tests. Hot working maps representing the influences of strains, strain rates, and temperatures were established. It was found that the power dissipation coefficient was not only related to the recrystallized grain size but was also related to the volume fraction of recrystallized grains. The optimal hot working parameters were suggested. This work provides comprehensive understanding of the hot workability of 300M steel in thermal compression.

Download Full-text

Study on Plastic Deformation Behavior of Mo-10Ta under Ultra-High Strain Rate

Metals ◽

10.3390/met10091153 ◽

2020 ◽

Vol 10 (9) ◽

pp. 1153

Author(s):

Ping Song ◽

Wen-Bin Li ◽

Yu Zheng ◽

Jiu-Peng Song ◽

Xiang-Cao Jiang ◽

...

Keyword(s):

Activation Energy ◽

High Strain Rate ◽

Strain Rate ◽

Strain Rate Sensitivity ◽

Deformation Behavior ◽

High Strain ◽

Rate Sensitivity ◽

Strain Rate Range ◽

Rate Range ◽

Strain Relationship

This study investigated the deformation behavior of the Mo-10Ta alloy with a strain rate range of 102–105 s−1. The Split Hopkinson pressure bar (SHPB) experiments were conducted to investigate the influence of deformation conditions on the stress-strain relationship and strain rate sensitivity of the material within a strain rate range of 0.001–4500 s−1. The Shaped Charge Jet (SCJ) forming experiments under detonation loading was conducted to clarify the dynamic response and microstructure evolution of the material within an ultra-high strain rates range of 104–105 s−1. Based on the stress-strain relationship of Mo-10Ta alloy at high temperature (286–873 K) and high strain rate (460–4500 s−1), the influence of temperature and strain rate on the activation energy Q was analyzed. The results indicate that the material strain rate sensitivity increased with the increase in strain rate and strain. Meanwhile, the activation energy Q decreased as the temperature and strain rate increased. The plasticity of the Mo-10Ta alloy under the condition of SCJ forming was substantially enhanced compared with that under quasi-static deformation. The material grain was also refined under ultra-high strain rate, as reflected by the reduction in grain size from 232 μm to less than 10 μm.

Download Full-text

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

Advances in Materials Science and Engineering ◽

10.1155/2019/6810326 ◽

2019 ◽

Vol 2019 ◽

pp. 1-6 ◽

Cited By ~ 1

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.

Download Full-text

Determination of Instability in Zr-2.5Nb-0.5Cu Using Lyapunov Function

Materials Science Forum ◽

10.4028/www.scientific.net/msf.830-831.329 ◽

2015 ◽

Vol 830-831 ◽

pp. 329-332 ◽

Cited By ~ 4

Author(s):

Kuldeep Kumar Saxena ◽

Vivek Pancholi ◽

Dinesh Srivastava ◽

G.K. Dey ◽

Sanjay K. Jha ◽

...

Keyword(s):

Lyapunov Function ◽

Strain Rate ◽

Flow Instability ◽

Peak Stress ◽

Strain Rate Range ◽

Rate Of Change ◽

Deformation Condition ◽

Hot Workability ◽

Lower Temperature

Hot workability of Zr-2.5Nb-0.5Cu alloy has been investigated by means of hot compression test using Gleeble-3800®, in the temperature and strain rate range of 700 to 925°C and 0.01-10s-1, respectively. Deformation behavior was characterized in terms of flow instability using peak stress with the help of Lyapunov Function. The true stress-strain curves shows that softening occurs at all lower temperature and for entire strain rates of deformation. The instable flow was suggested by negative m value at deformation condition of 700°C (5 and 10 s-1), while s value at 925°C (10 s-1). The combined result of rate of change of m and s with respect to log strain rate suggest that the deformation condition ranges from 725-780°C (10-2- 10-1 s-1) and 700°C (1-10 s-1) representing safe domain for stable flow.

Download Full-text

Characterization of Hot Deformation Behavior of Udimet720Li Superalloy Using Processing Map

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.887-888.1161 ◽

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.

Download Full-text

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

Materials ◽

10.3390/ma13020312 ◽

2020 ◽

Vol 13 (2) ◽

pp. 312 ◽

Cited By ~ 1

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.

Download Full-text

Flow Stress Equations for Type 304 Stainless and AISI 1055 Steels

Journal of Engineering Materials and Technology ◽

10.1115/1.3225798 ◽

1985 ◽

Vol 107 (2) ◽

pp. 97-100 ◽

Cited By ~ 15

Author(s):

P. Dadras

Keyword(s):

Experimental Data ◽

Stainless Steel ◽

Flow Stress ◽

Strain Rate ◽

Working Conditions ◽

Hot Working ◽

304 Stainless Steel ◽

Strain Behavior ◽

Type 304 ◽

Type 304 Stainless Steel

A model for stress-strain behavior under hot working conditions has been proposed. Based on experimental data, equations for the dependence of flow stress on strain, strain rate, and temperature have been developed. Application to type 304 stainless steel and AISI 1055 steel has been demonstrated.

Download Full-text

Dynamic Mechanical Response of Biomedical 316L Stainless Steel as Function of Strain Rate and Temperature

Bioinorganic Chemistry and Applications ◽

10.1155/2011/173782 ◽

2011 ◽

Vol 2011 ◽

pp. 1-13 ◽

Cited By ~ 21

Author(s):

Woei-Shyan Lee ◽

Tao-Hsing Chen ◽

Chi-Feng Lin ◽

Wen-Zhen Luo

Keyword(s):

Activation Energy ◽

Stainless Steel ◽

Flow Stress ◽

Strain Rate ◽

Thermal Activation ◽

316L Stainless Steel ◽

Rate Sensitivity ◽

Thermal Activation Energy ◽

Work Hardening Rate ◽

Stress Work

A split Hopkinson pressure bar is used to investigate the dynamic mechanical properties of biomedical 316L stainless steel under strain rates ranging from 1 × 103 s-1to 5 × 103 s-1and temperatures between25∘Cand800∘C. The results indicate that the flow stress, work-hardening rate, strain rate sensitivity, and thermal activation energy are all significantly dependent on the strain, strain rate, and temperature. For a constant temperature, the flow stress, work-hardening rate, and strain rate sensitivity increase with increasing strain rate, while the thermal activation energy decreases. Catastrophic failure occurs only for the specimens deformed at a strain rate of 5 × 103 s-1and temperatures of25∘Cor200∘C. Scanning electron microscopy observations show that the specimens fracture in a ductile shear mode. Optical microscopy analyses reveal that the number of slip bands within the grains increases with an increasing strain rate. Moreover, a dynamic recrystallisation of the deformed microstructure is observed in the specimens tested at the highest temperature of800∘C.

Download Full-text