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Exfoliation corrosion initiated after 30 minutes in the coarse-grained structure (279μm), whereas it was delayed to 60 minutes in the fine-grained structure (75μm) and further to 75 minutes in the ultrafine-grained structure (39μm).
Previous studies have investigated the influence of grain aspect ratio on the origination of exfoliation corrosion in elongated grains.
This is attributed to the increased grain boundary density on the corroded surface associated with higher aspect ratios, as oxide films formed during the initial stages of corrosion tend to be thinner at grain boundaries, thus, increasing the number of corrosion initiation sites and accelerating the origination of exfoliation corrosion.
In the fine-grained microstructure, the small grain size restricts dislocation movement within the grains, promoting dislocation annihilation at grain boundaries [4].
Furthermore, even within coarse-grained microstructures, in grains that do not contain shear bands, passive film growth depends on intragranular processes due to the low grain boundary density.

Annealed pure copper was subjected to equal-channel angular pressing (ECAP) by route Bc for different passes number.
Depending on the number of ECAP passes or collected true strain the microstructure parameters such as grain size, dislocation density and angle of grain boundaries are different [9].
Depending on ECAP passes number and therefore formed grain sizes, the specimens were classified as follow: N1 -CG, annealed; N2 - 4 ECAP passes by Bc route; N3 - 8 passes; N4 - after 10 passes.
Investigations established that during HCV deformation at stabile stress amplitude the grain size had not changed in dimensions as the cycles number is limited up to 20-30 as maximal.
During HCV deformation the dislocation density decreases and depends on cycle's number, amplitude and frequency.

Next, these lamellas are subdivided by transverse LABs into sub-grains and/or (sub)grains bounded partly by LABs and partly by HABs (Fig. 2a).
However, certain grain orientations are resistant to CDRX, and large remnants of initial grains remain (Fig. 2b).
The size of the grains and (sub)grains remained nearly unchanged.
The number of dislocations emitted by sources was significantly higher than the number of dislocations consumed for the formation of LABs with misorientation less than 2º.
In this stage, the number of lattice dislocations accumulated by deformation-induced boundaries exceeds the number of dislocations stored within the interiors of the round crystallites.

Grain size in N-T specimen is limited to less than 2 μm, whilst over 2μm grains exist in HR specimen.
These heterogeneous grains in IPF map correspond to the coarse grains shown in Fig. 2(b).
From ODF maps of N-T and HR specimens, red grains with {100}<011> and green grains with {110}<011> could be the residual ferrite[5].
Hence, heterogeneously coarse grains in HR specimen are considered to be transformed ferrite from the HRed γ-austenite grains.
This process induced a formation of the coarse ferrite grains from the severely hot rolled γ-grains.

Ferrite Number The effect of sub-zero temperature on ferrite number is shown in Figure 1.
The yield strength increased significantly from 191 MPa for ferrite number 5 to 863 MPa for ferrite number 65.
The value of UTS increased from 1180 MPa for ferrite number 5 to 1418 MPa for ferrite number 65.
Effect of martensite reversion on the formation of nano/submicron grained AISI 301 stainless steel, Materials Characterization 63 (2009) 1220-1223
Formation of nano-grained structure in a 301 stainless steel using a repetitive thermo-mechanical treatment, Materials Letters 63(2009) 1442-1444 [5] Karpov LP.

The fracture was characterized by ductile fracture due to existence of a large number of dimples. 1 Introduction According to the Hall–Petch relationship, the average grain size of the material plays a significant role in determining the mechanical and physical properties of crystalline materials.
The spacing between each band is approximately 100-500nm.The smaller grains appear to be equiaxed whereas the larger grains are elongated.
The dimples in the fracture zone are mainly large and deep, and their number is high.
It is found that there are a large number of equiaxial dimple.
The average dimple size gradually decreases with increasing number of DECLE passes, which was beneficial to enhance the mechanical properties.

Measurements of the Vickers microhardness showed improving hardness homogeneity with increasing numbers of HPT turns.
It is readily apparent that the structure before HPT processing contained nearly equiaxed grains with an average grain size of about 10.5 μm.
Thirdly, the samples processed by HPT under 6 GPa had relatively higher hardness compared with samples processed under 3 GPa for the same number of HPT revolutions.
The ω phase has been detected in HPT processed HP and CP Ti at various pressures and for various numbers of rotations of the HPT die [16,17].
The commercially pure Ti attained equiaxed grains with a grain size of ~105 nm after HPT under 6 GPa for 20 turns.

Tensile Properties and Fatigue strength of Ultrafine Grained Pure Copper M.
Oxygen-free copper was processed by equal channel angular pressing with different numbers of ECAP process cycles, NP.
Here, the terms 1P, 4P and 8P mean the materials processed with the number of ECAP process cycles NP = 1, 4 and 8, respectively.
After the 8th pressing (c), no change in grain size was recognized, however the GB (grain boundary) contours appear to recover their sharpness.
The high HF values in UFG copper after formation of exiaxed grains indicated that the existence of non-equilibrium grain boundaries (N-E GBs) [2].

According to different experimental data the grain boundary diffusion the triple product (P) can change in opposite directions after alloying.
The grain boundaries in polycrystals are less studied objects.
The situation became more difficult if we speak about grain boundary diffusion (GBD).
One can find a number of results, demonstrated the depletion of the GBD by alloying.
Increasing of K value increases the number of Cu atoms participated in atomic complexes formation and excluded from the diffusion process.

The assumptions numbered 1 and 2 and 3 are essentially correct.
Statistically, any grain moves along its grain boundary a mean “flight time” .
The increment of section can be calculated if we consider that in a time period a number of grains N0 moves a distance w, N0 being the number of grains of the sample.
Let W be the average volume of a grain (W»d3, d being the average grain size).
Accordingly, the number of grains displaced to the lateral faces of the sample will be given by: (2) Since the number of available sites along the lateral faces is SL/d2 (being SL the lateral faces area), the radial increment of the surface per unit time would be .