scholarly journals Fine Structure of Shear Bands Formed during Hot Deformation of Two Austenitic Steels

2004 ◽  
Vol 45 (7) ◽  
pp. 2157-2164 ◽  
Author(s):  
Pavel Cizek ◽  
Fang Bai ◽  
W.Mark Rainforth ◽  
John H. Beynon
Keyword(s):  
Fine Structure ◽  
Hot Deformation ◽  
Shear Bands ◽  
Austenitic Steels

Hot working of SP-700 titanium alloy with lamellar α + β starting structure using a processing map

2020 ◽  
Vol 111 (4) ◽  
pp. 297-306
Author(s):  
Amir Hosein Sheikhali ◽  
Maryam Morakkabati
Keyword(s):  
Titanium Alloy ◽  
Strain Rate ◽  
Hot Deformation ◽  
Processing Map ◽  
Microstructural Analysis ◽  
Shear Bands ◽  
Alpha Phase ◽  
Strain Rates ◽  
Compression Tests ◽  
Temperature Range

Abstract In this study, hot deformation behavior of SP-700 titanium alloy was investigated by hot compression tests in the temperature range of 700-9508C and at strain rates of 0.001, 0.1, and 1 s-1. Final mechanical properties of the alloy (hot compressed at different strain rates and temperatures) were investigated using a shear punch testing method at room temperature. The flow curves of the alloy indicated that the yield point phenomenon occurs in the temperature range of 800- 9508C and strain rates of 0.1 and 1 s-1. The microstructural analysis showed that dynamic globularization of the lamellar α phase starts at 7008C and completes at 8008C. The alpha phase was completely eliminated from b matrix due to deformation- induced transformation at 8508C. The microstructure of specimens compressed at 8508C and strain rates of 0.001 and 0.1 s-1showed the serration of beta grain boundaries, whereas partial dynamic recrystallization caused a necklace structure by increasing strain rate up to 1 s-1. The specimen deformed at 7008C and strain rate of 1 s-1was located in the instability region and localized shear bands formed due to the low thermal conductivity of the alloy. The processing map of the alloy exhibited a peak efficiency domain of 54% in the temperature range of 780-8108C and strain rates of 0.001- 0.008 s-1. The hot deformation activation energy of the alloy in the α/β region (305.5 kJ mol-1) was higher than that in the single-phase β region (165.2 kJ mol-1) due to the dynamic globularization of the lamellar a phase.

scholarly journals Hot Deformation Behavior of Cu–Sn–La Polycrystalline Alloy Prepared by Upcasting

Materials ◽  
2020 ◽  
Vol 13 (17) ◽  
pp. 3739
Author(s):  
Siming Hua ◽  
Pingze Zhang ◽  
Zili Liu ◽  
Lin Yang
Keyword(s):  
Dynamic Recrystallization ◽  
Hot Deformation ◽  
Deformation Behavior ◽  
Testing Machine ◽  
Shear Bands ◽  
Strain Curve ◽  
Extrusion Process ◽  
Hot Deformation Behavior ◽  
Polycrystalline Alloy ◽  
Promising Application

In this study, the hot deformation of a Cu–0.55Sn–0.08La (wt.%) alloy was studied using a Gleeble-3180 testing machine at deformation temperatures of 400–700 °C and various strain rates. The stress–strain curve showed that the hot deformation behavior of the Cu–0.55Sn–0.08La (wt.%) alloy was significantly affected by work hardening, dynamic recovery, and dynamic recrystallization. The activation energy Q was 261.649 kJ·mol−1 and hot compression constitutive equation was determined as  ε˙=[sinh(0.00651σ)]10.2378·exp(33.6656−261.649RT). The microstructural evolution of the alloy during deformation at 400 °C revealed the presence of both slip and shear bands in the grains. At 700 °C, dynamic recrystallization grains were observed, but recrystallization was incomplete. In summary, these results provide the theoretical basis for the continuous extrusion process of alloys with promising application prospects in the future.

Studies on Ductile Damage and Flow Instabilities during Hot Deformation of a Multiphase γ-TiAl Alloy

2014 ◽  
Vol 611-612 ◽  
pp. 99-105 ◽  
Author(s):  
Dilek Halici ◽  
Hassan Adrian Zamani ◽  
Daniel Prodinger ◽  
Cecilia Poletti ◽  
Daniel Huber ◽  
...  
Keyword(s):  
Hot Deformation ◽  
Titanium Aluminide ◽  
Titanium Aluminides ◽  
Turbine Blades ◽  
Shear Bands ◽  
Flow Instabilities ◽  
Ductile Damage ◽  
Gamma Titanium Aluminide ◽  
Gamma Titanium ◽  
Damage Models

Gamma titanium aluminides are promising alloys for low-pressure turbine blades. A significant disadvantage of such intermetallic alloys is failure induced during forming processes due to ductile damage and flow instabilities. Previous investigations on a gamma titanium aluminide alloy (TNM), have shown ductile damage due to tensile stress components and instabilities such as shear bands, pores and micro-cracks at low temperatures and high strain rates. The main part of the current work is to delineate damage and unstable regions in the low temperature region. Hot deformation experiments are conducted on a Gleeble®3800 thermomechanical treatment simulator to obtain flow curves to be implemented in a finite element method (FEM) code. Instabilities in the material are described by existing instability criteria as proposed by Semiatin and Jonas and implemented into FEM code DEFORMTM 2D. Predictions of ductile damage models and the instability parameter are validated through detailed microstructural studies of deformed specimens analysed by light optical- and scanning electron microscopy.

TRIP Effect and Deformation Damaging of Metastable Austenitic Steels

2007 ◽  
Vol 539-543 ◽  
pp. 4903-4908 ◽  
Author(s):  
H. Oettel ◽  
M. Glavatskikh ◽  
U. Martin ◽  
A. Nikulin
Keyword(s):  
Crack Formation ◽  
Uniform Elongation ◽  
Shear Bands ◽  
Local Deformation ◽  
Austenitic Steels ◽  
Low Flow ◽  
Trip Effect ◽  
Fracture Path ◽  
Continuous Transformation ◽  
Additional Hardening

The TRIP – effect in metastable austenitic steels is caused by a moderate local martensitic transformation, connected with an extraordinary increase e.g. of the uniform elongation in tensile testing. In this case the martensite formation causes an additional hardening effect, preventing the local deformation as well as damaging during plastic deformation. The main conditions of a marked TRIP – effect is a low flow stress in the undeformed state, a high strengthening exponent, a continuous transformation up to about 20 % martensite and a high resistance against damaging (e.g. crack formation and propagation). The martensite transformation starts in glide or shear bands and their crossings also at temperatures clearly above the conventional Md – temperatures, reducing the stress local concentrations and so preventing damaging. Furthermore, high martensite contents can be detected along the fracture path, indicating the hindering of the crack propagation by the transformation. To demonstrate the influence of damaging on the TRIP – effect the deviations from the so-called Considere-criterion for uniform elongation can be used. Related to the deformation the damaging under TRIP – conditions is minimal.

Hot Deformation Behavior of Ti-6Al-4V Alloy with a Transitional Microstructure in the Isothermal Hot Compression

2014 ◽  
Vol 1019 ◽  
pp. 273-279 ◽  
Author(s):  
Yong Xu ◽  
Xiang Jie Yang ◽  
Xiong Xin Jiang ◽  
Yi He ◽  
Dan Ni Du
Keyword(s):  
Strain Rate ◽  
Hot Deformation ◽  
Deformation Behavior ◽  
Flow Instability ◽  
Testing Machine ◽  
Shear Bands ◽  
Hot Deformation Behavior ◽  
Factors Affecting ◽  
Working Region ◽  
Gleeble 3500

The hot deformation behavior of Ti-6Al-4V alloy with transitional microstructure over temperature 800°C~950°C and strain rate ranges of 0.001~10s-1 has been studied by Gleeble-3500 hot working simulation testing machine. The flow softening of stress-strain curves is resulted from the spheroidization of transitional microstructure, dynamic recrystallization and superplasticity. Both temperature and strain rate are important factors affecting the deformation behavior. Flow instability induced by adiabatic shear bands occurs at 800-880°Cand 0.32-10 s-1. With the increasing of strain rate and decreasing of temperature, the degree of strain localization increases. The optimum working region of Ti-6Al-4V alloy with a transitional microstructure is at 820-910°C and 0.001-0.1 s-1.

scholarly journals Hot Deformation Response of Al 6061-MWCNTs Alloy Composites

2019 ◽  
Vol 8 (12) ◽  
pp. 27-32
Keyword(s):  
Hot Deformation ◽  
Processing Map ◽  
Shear Bands ◽  
Processing Parameters ◽  
Hot Compression ◽  
Compression Tests ◽  
Sem Images ◽  
Al 6061 ◽  
Characterization Study ◽  
Multi Walled Carbon Nanotubes

In this investigation, the effect of multi walled carbon nanotubes (MWCNTs) on compressive response with Al 6061 alloy nanocomposites prepared by mechanical alloying has been investigated. Hot deformation tests required to develop processing map were conducted at three temperatures such as 250, 350 and 450°C and in the three strain rates of 0.01, 0.1 and 1.0 s-1 . The development of geometric dynamic recrystallization (DRX), dynamic recovery (DRV), instability regions and shear bands were confirmed by characterization study of prepared nanocomposites after hot Compression tests. The average activation energies for hot compression response was calculated as 153.00 KJ/mole for 2 wt.% MWCNTs reinforced Al 6061 alloy (AA 6061) nanocomposites. The most favorable key processing parameters for hot deformation was identified as temperature between 370-450°C and the range of strain rate was 0.1- 0.01s -1 . The region which are prone to shear localization, cracks and other instability were identified using the processing map and the same was verified with microstructural images obtained using optical and SEM images.

Effect of Hot Deformation Temperature on the Restoration Mechanisms and Texture in a High-Cr Ferritic Stainless Steel

2013 ◽  
Vol 762 ◽  
pp. 705-710 ◽  
Author(s):  
Saara Mehtonen ◽  
L. Pentti Karjalainen ◽  
David A. Porter
Keyword(s):  
Stainless Steel ◽  
Ferritic Stainless Steel ◽  
Hot Deformation ◽  
Deformation Temperature ◽  
Electron Backscatter Diffraction ◽  
Shear Bands ◽  
Compression Tests ◽  
Recrystallized Grain Size ◽  
Evolution Of Microstructure ◽  
Backscatter Diffraction

The effect of hot deformation temperature on the deformed microstructures and evolution of microstructure and texture of a 21Cr Ti-Nb dual-stabilized ferritic stainless steel was studied using plane strain hot compression tests on a Gleeble 1500 thermomechanical simulator. The deformation was carried out at 550 - 950 °C with a strain of 0.5 at 1 s-1. The compression was followed by fast cooling to room temperature in order to study the deformed microstructures. Some specimens were heated from the deformation stage to either 750 or 950 °C and held for 0 or 30 s in order to study the nucleation process of recrystallization. The electron backscatter diffraction technique was used to analyze the resultant microstructures and textures. Lowering of the deformation temperature increased the rate of static recrystallization (SRX) and decreased the recrystallized grain size. After deformation at 550 and 600 °C and complete SRX, beneficial γ-fibre texture formed presumably as a result of nucleation at in-grain shear bands. SRX after deformation at 750 °C or above led to the formation of harmful α-fibre textures with weak γ-fibre.

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