Geometrically Necessary Dislocations in Deformed Martensitic Steel

2014 ◽  
Vol 1013 ◽  
pp. 23-30 ◽  
Author(s):  
Nina Koneva ◽  
Natal'ya Popova ◽  
Marina Fedorischeva ◽  
Eduard Kozlov
Keyword(s):  
Plastic Deformation ◽  
Dislocation Density ◽  
Structure Formation ◽  
Defect Structure ◽  
Martensitic Steel ◽  
Deformation Mechanisms ◽  
Main Attention ◽  
Structural Formation

Effect of a size of closed structural formation on accumulation of dislocation density and its components at plastic deformation is studied. Main attention is given to a role of a division of boundaries of a different type. Structural formation sizes are determined and different parameters of structure defining micro-and mezolevel at development of plastic deformation mechanisms are distinguished. A role of statistically stored dislocations (SSD) and geometrically necessary dislocations (GND) for defect structure formation of a material is examined. It is determined that than a size of closed structural formation is less than that a component of GND is larger and component of SSD is less. The work is based on results of TEM reserches of a structure of deformed materials.

The Influence of Plastic Deformation on Lattice Defect Structure and Mechanical Properties of 316L Austenitic Stainless Steel

2017 ◽  
Vol 885 ◽  
pp. 13-18 ◽  
Author(s):  
Moustafa El-Tahawy ◽  
Jenő Gubicza ◽  
Yi Huang ◽  
Hye Lim Choi ◽  
Hee Man Choe ◽  
...  
Keyword(s):  
Plastic Deformation ◽  
Stainless Steel ◽  
Dislocation Density ◽  
Defect Structure ◽  
High Pressure Torsion ◽  
Defect Density ◽  
Lattice Defect ◽  
Coarse Grained ◽  
316L Austenitic Stainless Steel ◽  
Processed Sample

The effect of different plastic deformation methods on the phase composition, lattice defect structure and hardness in 316L stainless steel was studied. The initial coarse-grained γ-austenite was deformed by cold rolling (CR) or high-pressure torsion (HPT). It was found that the two methods yielded very different phase compositions and microstructures. Martensitic phase transformation was not observed during CR with a thickness reduction of 20%. In γ-austenite phase in addition to the high dislocation density (~10 × 1014 m-2) a significant amount of twin-faults was detected due to the low stacking fault energy. On the other hand, γ-austenite was gradually transformed into ε and α’-martensites with transformation sequences γ→ε→α’ during HPT deformation. A large dislocation density (~133 × 1014 m-2) was detected in the main phase (α’-martensite) at the periphery of the disk after 10 turns of HPT. The high defect density is accompanied by a very small grain size of ~45 nm in the HPT-processed sample, resulting in an very large hardness of 6130 MPa.

Defect Structure Parameters of Deformed Polycrystals on Micro- and Mesolevel of Grain Sizes

2014 ◽  
Vol 1013 ◽  
pp. 1-6
Author(s):  
Eduard Kozlov ◽  
Natal'ya Popova ◽  
Marina Fedorischeva ◽  
Nina Koneva
Keyword(s):  
Plastic Deformation ◽  
Size Effect ◽  
Defect Structure ◽  
Structure Parameters ◽  
Scalar Density ◽  
Grain Sizes ◽  
Different Types ◽  
Closed Structure ◽  
Mechanisms Of Plastic Deformation

In the paper we consider the size effect of the closed structural formations as the function of accumulation of scalar density dislocations and their components under plastic deformation. The focus is on the role of interfaces of different types. The sizes are determined and the various parameters of the structure defining the micro-and mesolevel are identified at the development of the mechanisms of plastic deformation. The role of statistically stored dislocations (SSD) and geometrically necessary dislocations (GND) in the formation of the defect structure of the material is examined. It has been established that the smaller the size of the closed structure, the greater the GND part and the smaller the SSD component. The work is based on the TEM research of the structure of deformed materials.

Activation Volume in Fine Grained Metals from Stress Relaxation and Nano-Indentation

2008 ◽  
Vol 584-586 ◽  
pp. 399-404 ◽  
Author(s):  
Yannick Champion ◽  
Sophie Nowak
Keyword(s):  
Plastic Deformation ◽  
Stress Relaxation ◽  
Dislocation Density ◽  
Deformation Mechanism ◽  
Activation Volume ◽  
Testing Technique ◽  
Nano Indentation ◽  
Fine Grained

Fine grained copper was studied using the stress relaxation technique and creep testing in nano-indentation, to determine the activation volume involved in the micro-mechanism of the deformation. This material exhibits a near-perfect elasto-plastic deformation, featured by a steep work-hardening, after the elastic domain, followed by flow at a constant stress. Measurements of the activation volumes in the various domains reveal the role of the dislocations and the variation in the dislocation density in the deformation mechanism. This emphasizes the importance, in the determination of the activation volume, of the deformation domain investigated as well as the testing technique used and whether in both cases, the measurement is carried out in a transient domain or condition where variation in dislocation density occurs.

scholarly journals The role of plastic deformation mechanisms in high temperature sintering of the particles

2013 ◽  
Vol 3 (4) ◽  
pp. 315-317
Author(s):  
M. I. Alymov ◽  
S. I. Averin ◽  
V. S. Shustov ◽  
L. V. Gordopolova
Keyword(s):  
Plastic Deformation ◽  
High Temperature ◽  
Deformation Mechanisms

Defect Structure Evolution in HCP-Zirconium Alloys: The Role of Anisotropy

2014 ◽  
Vol 1013 ◽  
pp. 62-66
Author(s):  
Tomara Poletika ◽  
Svetlana Girsova ◽  
Natal'ya Popova ◽  
Eduard Kozlov ◽  
Nina Koneva
Keyword(s):  
Plastic Deformation ◽  
Electron Microscope ◽  
Dislocation Structure ◽  
Defect Structure ◽  
Polycrystalline Material ◽  
Zirconium Alloys ◽  
Structure Evolution ◽  
Internal Stresses

The evolution of the dislocation structure and the ensemble of boundaries during plastic deformation of Zr-Nb alloys studied using electron microscope. The role of the anisotropy of slip in the formation and restructuring of the boundaries, recurrence of dislocation transformation was established. Special emphasis is placed on specific features of geometrically necessary defects evolution. It was found that the geometrically necessary boundaries formation involves an athermal coalescence as a mechanism of relaxation of large accumulated internal stresses, which prevents fracture in an anisotropic polycrystalline material.

Investigation of shock-wave deformation history from recovered structure

1986 ◽  
Vol 44 ◽  
pp. 434-435
Author(s):  
M.A. Mogilevsky ◽  
L.S. Bushnev
Keyword(s):  
Shock Wave ◽  
Plastic Deformation ◽  
Dislocation Density ◽  
Shock Waves ◽  
Shock Front ◽  
Single Crystals ◽  
Residual Deformation ◽  
Deformation Structure ◽  
Deformation History ◽  
Deformation Velocity

Single crystals of Al were loaded by 15 to 40 GPa shock waves at 77 K with a pulse duration of 1.0 to 0.5 μs and a residual deformation of ∼1%. The analysis of deformation structure peculiarities allows the deformation history to be re-established.After a 20 to 40 GPa loading the dislocation density in the recovered samples was about 1010 cm-2. By measuring the thickness of the 40 GPa shock front in Al, a plastic deformation velocity of 1.07 x 108 s-1 is obtained, from where the moving dislocation density at the front is 7 x 1010 cm-2. A very small part of dislocations moves during the whole time of compression, i.e. a total dislocation density at the front must be in excess of this value by one or two orders. Consequently, due to extremely high stresses, at the front there exists a very unstable structure which is rearranged later with a noticeable decrease in dislocation density.

Sign in / Sign up

Export Citation Format

Share Document