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.

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

2015 ◽  
Vol 830-831 ◽  
pp. 329-332 ◽  
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.

Hot Workability of a High Strength Low Alloy Steel for Construction Application

2012 ◽  
Vol 724 ◽  
pp. 178-181
Author(s):  
Woo Young Jung ◽  
Tae Kwon Ha
Keyword(s):  
Strain Rate ◽  
Power Dissipation ◽  
High Efficiency ◽  
Hsla Steel ◽  
High Strength ◽  
Plastic Instability ◽  
Strain Rate Range ◽  
Hot Workability ◽  
Compression Tests ◽  
Increasing Temperature

The hot deformation behavior of a high strength low alloy (HSLA) steel for construction application under hot working conditions in the temperature range of 900 to 1100 and strain rate range from 0.1 to 10 s-1 has been studied by performing a series of hot compression tests. The dynamic materials model has been employed for developing the processing maps, which show variation of the efficiency of power dissipation with temperature and strain rate. Also the Kumars model has been used for developing the instability map, which shows variation of the instability for plastic deformation with temperature and strain rate. The efficiency of power dissipation increased with decreasing strain rate and increasing temperature. High efficiency of power dissipation over 20 % was obtained at a finite strain level of 0.3 under the conditions of strain rate lower than 1 s-1 and temperature higher than 1050. Plastic instability was expected in the regime of temperatures lower than 1000°C and strain rate lower than 0.3 s-1.

Effect of Melting Processing on Tensile Properties and Microstructure of New RAFM Steel

2010 ◽  
Author(s):  
Jun Yao ◽  
Jinping Suo
Keyword(s):  
Tensile Strength ◽  
Tensile Properties ◽  
Hot Forging ◽  
Total Elongation ◽  
Thermal Ageing ◽  
Vacuum Induction Melting ◽  
Induction Melting ◽  
The Difference ◽  
Rafm Steel ◽  
Better Than

All of the RAFM steels only safely used under 550°C, that is not enough for the next reactor. An new RAFM steel was melted by non-vacuum induction melting (VIM) and electro-slag remelting (ESR), followed by hot-forging and rolling into rods and plates. In this paper, we investigated the effect of thermal ageing treatment on tensile properties of the rods and plates. The microstructure was studied by OM (optics micrograph) and scanning electron microscopy (SEM). The results showed that by using the same heat treatment process, the tensile strength of the samples was 680MPa, the total elongation was 31%, which were better than the CLAM steel whose tensile strength and total elongation were 668MPa and 25% respectively. The difference between the transverse and the longitudinal properties was reduced markedly. So the ESR played an important part in improving the mechanical properties.

scholarly journals Effect of strain rate on mechanical properties and microstructure of TRIP steel

2021 ◽  
Vol 252 ◽  
pp. 02058
Author(s):  
Libo Pan ◽  
Wanjun Zhu ◽  
Zhaojun Deng ◽  
Zhijiang Zuo
Keyword(s):  
Mechanical Properties ◽  
Strain Rate ◽  
Trip Steel ◽  
Volume Fraction ◽  
Aging Effect ◽  
Tensile Tests ◽  
Total Elongation ◽  
Dynamic Strain ◽  
Soaking Time ◽  
The Difference

TRIP effect is one of the important features for TRIP steel. A Nb-Mo microalloyed TRIP steel was developed by employing two different soaking time during annealing, and tensile tests at three different strain rate for specimens after annealing were performed. The microstructures and the volume fraction of retained martensite were examined and analyzed. The result indicated that TRIP steel showed significantly different behaviour at different strain rates. The ultimate tensile strength and total elongation decreased with the strain rate increasing. The dynamic strain aging effect might occur at low strain rate. With shorter soaking time during annealing, microstructure with ultra-refined grain size could be achieved. Fracture surfaces were different at different strain rate. As strain rate increases, the fraction of retained austenite to martensite transformation at failure point decreases which leads to the difference of mechanical properties.

Establishment of Processing Maps for 25vol.% B4CP/AA6061 Composite and its Application in Hot Pack-Rolling Process

2018 ◽  
Vol 913 ◽  
pp. 498-508
Author(s):  
Sheng Pu Liu ◽  
De Fu Li ◽  
Sheng Li Guo ◽  
Peng Du
Keyword(s):  
Rolling Process ◽  
Processing Parameters ◽  
Strain Rate Range ◽  
Processing Maps ◽  
Hot Workability ◽  
Rolling Velocity ◽  
Surface Cracking ◽  
Pack Rolling ◽  
Edge Cracking ◽  
Hot Pack

The hot workability and hot pack-rolling process of B4CP/AA6061 composite were studied. The results showed that the addition of B4C particles could effectively promote the dynamic recrystallization (DRX) process of the composite. DRX and DRX grains growth were dominant deformation mechanism during hot deformation of B4CP/AA6061composite. Typical instability defects included micro voids and particle aggregation. The optimum processing parameters for good workability were obtained in the temperature range of 450°C-500°C and strain rate range of 0.01s-1-0.1s-1. According to the flow stress curves and processing maps, a temperature of 500°C and a rolling velocity of 40 mm/s were chosen for pack-rolling experiments. The pack-rolled composite sheets in the RD and TD showed more homogeneous DRX grains than as-HIPed microstructures, which might indicate that hot pack-rolling could lead to more homogeneous microstructures without any edge cracking and surface cracking.

scholarly journals Hot Deformation Behaviors of as Cast 321 Austenitic Stainless Steel

Metals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 1245
Author(s):  
Deli Zhao ◽  
Liguo Ren ◽  
Yong Wang ◽  
Wei Wang ◽  
Zhe Zhu ◽  
...  
Keyword(s):  
Activation Energy ◽  
Stainless Steel ◽  
Strain Rate ◽  
Nuclear Power ◽  
Physical Simulation ◽  
Strain Rate Range ◽  
Electron Back Scatter Diffraction ◽  
Hot Working ◽  
Hot Workability ◽  
Nuclear Power Reactor

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.

scholarly journals Evaluation of Hot Workability of Powder Metallurgy Ni-Based Superalloy with Different Initial Microstructures

2020 ◽  
Vol 52 (1) ◽  
pp. 181-193
Author(s):  
Masaya Higashi ◽  
Naoya Kanno
Keyword(s):  
Grain Size ◽  
Powder Metallurgy ◽  
Strain Rate ◽  
Hot Isostatic Pressing ◽  
Hot Extrusion ◽  
Strain Rate Range ◽  
Coarse Grained ◽  
Hot Workability ◽  
Fine Grained ◽  
Nucleation Sites

AbstractThe effect of the initial microstructure on the hot workability of a powder metallurgy Ni-based superalloy was investigated in the high-temperature range of 950 °C to 1180 °C and strain rate range of 0.001 to 1.0 s−1. Six samples with different initial microstructures were fabricated by various hot isostatic pressing (HIP) conditions and subsequent treatments such as hot extrusion. The coarse-grained samples exhibited low hot workability regardless of the deformation conditions. In contrast, the hot workability of the fine-grained samples significantly varied depending on the deformation conditions. The hot workability exhibited a peak at the sub-solvus temperature of ~ 1100 °C and decreased at temperatures higher and lower than this temperature. In addition, the hot workability decreased monotonically with increasing the strain rate. The prior particle boundaries (PPBs) acted as cavity nucleation sites and crack paths, especially at lower temperatures and higher strain rates, resulting in early fracture and low hot workability. With decreasing the grain size, the hot workability at the peak temperature improved. The extruded sample with the smallest grain size exhibited the best hot workability, owing to the avoidance of PPB fracture and the acceleration of dynamic recrystallization.

High Strain Rate Superplasticity in an Al-Mg-Sc-Zr Alloy Produced by Equal Channel Angular Pressing and Subsequent Cold and Warm Rolling

2012 ◽  
Vol 710 ◽  
pp. 223-228 ◽  
Author(s):  
Elena Avtokratova ◽  
Oleg Sitdikov ◽  
Oksana Mukhametdinova ◽  
Michael Markushev
Keyword(s):  
Grain Size ◽  
Strain Rate ◽  
Equal Channel Angular Pressing ◽  
Volume Fraction ◽  
Warm Rolling ◽  
Strain Rate Range ◽  
Ambient Temperatures ◽  
Angular Pressing ◽  
The Difference ◽  
Zr Alloy

Superplastic (SP) properties of an Al−5%Mg−0.2%Sc−0.08%Zr alloy subjected to equal channel angular pressing (ECAP) at T=325°C with an effective stain of ~ 8 and subsequent rolling at the same and ambient temperatures were studied. It has been shown that the formation of ultrafine grained (UFG) structure with the grain size of about 1 μm and the volume fraction 0.6-0.7 under ECAP resulted in exceptionally high SP ductilities in a wide temperature - strain rate range. Maximum elongations ~3300% appeared at 475°C and the strain rate () of 5.6×10-2s-1. Subsequent warm rolling with a total reduction of 86% led to increased to 0.8-0.85 volume fraction of ultrafine grains with no changes in grain size. Cold rolling with reduction of 80%, in contrast, provided a heavily deformed structure with high dislocation density. In spite of the difference in the alloy microstructures, the SP properties in both rolled conditions were close to similar. The both states exhibited SP behavior with maximum elongation of ~ 2800% at 520°C and = 1.4 ×10-2s-1.

Deformation Behavior of An O + β0 Processed Ti-21 Ai-23Nb Alloy at High Temperatures

1994 ◽  
Vol 364 ◽  
Author(s):  
Venkat Seetharaman
Keyword(s):  
Strain Rate ◽  
High Temperatures ◽  
High Volume ◽  
Strain Rate Range ◽  
Dynamic Strain ◽  
Initial Structure ◽  
Hot Workability ◽  
Compression Tests ◽  
Nominal Strain Rate ◽  
Heat Treated

AbstractA hot workability study was conducted on an orthorhombic Ti-21AI-23Nb alloy using isothermal, constant velocity compression tests, over the temperature range 900–1155°C and nominal strain rate range 0.001 to 1.0 s−1. Three different microstructures corresponding to (a) hot rolled and mill annealed, (b) β0 -heat treated, and (c) β0 solution treated and direct aged conditions were examined. These microstructures varied from a relatively coarse distribution of O-phase precipitates in a matrix of transformed βO to the metastable retained βO. Flow stress displayed a sharp dependence on temperature, strain rate and on the initial structure. While uniform plastic flow was obtained at high temperatures and for structures containing primary O, βO-heat treated structures led to pronounced flow softening. Strong yield point phenomena and serrated flow were observed in selected test conditions and for microstructures containing high volume fractions of metastable βO. These flow instabilities resulting from Luder band propagation and dynamic strain aging are interpreted in terms of dislocation interactions in supersaturated βO.

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

Metals ◽  
2019 ◽  
Vol 9 (8) ◽  
pp. 880 ◽  
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.

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