Search results

The composites fabricated with each number of cycles are called 5C, 8C, and 10C.
As increasing the number of cycles, both tensile strength and elongation increased, indicating that mechanical properties improved with an increase in the number of cycles.
Fig. 4 shows the relative comparison among two-dimensional local grain number dispersity (LN2DR) of Al2O3 particles measured by SEM and EBSD, the particle volume fraction, the particle density, the average grain size of aluminum, and the large-angle grains of aluminum matrix, and the field ratio and the local misorientation (KAL) (an index representing the plastic strain gradient in a microregion) in 5C, 8C, and 10C composites.
Comparison of microstructure parameters such as LN2DR, number of density of particles, average aluminum grain size, high angle grain boundary fraction (HAGBs), and kernel average misorientation (KAL) in composites after ARB with 8 and 8 cycles.
A uniform distribution of fine grains would introduce more high-angle grain boundaries and refine the grains.

The fresh dislocations multiply from the Frank-Read sources within the grains, and pile up against the twin and grain boundaries of two kinds of specimens.
Although there were many annealing twins, the grown-in dislocations were quite uniformly distributed in the surface grains.
Fig. 1 Typical pile-up dislocations in Cu-6.8at%Al alloys etched under pulling in tension: (a) a stress of 17 MPa at a true strain of 0.05 %; (b) a stress of 26 MPa at a true strain of 0.1 %. 20µm (a) Tensile direction Twin boundary Grown-in dislocations Pile-up dislocations Grain boundary 50µm (b) Tensile direction Secondary slip plane Grain boundary Primary slip plane Although the number of dislocations in the pile-up groups became about two-thirds of that for tensile loading, the distance of them spread within the grains.
It was confirmed that the fresh dislocations multiplied from the Frank-Read sources within the grains, and piled up against the twin and grain boundaries of two kinds of specimens.
Compressive direction 20µm (a) Pile-up dislocations Grain boundary 20µm Compressive direction (b) Twin boundary Grain boundary Pile-up dislocations

However, the previous process takes place retarded in comparison to fully austenitic steels [7] due to the smaller number of internal austenite-austenite grain boundaries.
The crystallite size of the ferrite grains and/or subgrains was determined by using a grain tolerance angle of 0.5°.
The IPF coloring plot in Figure 3a shows small recrystallized grains at prior austenite-austenite grain boundaries.
As can be seen in Table 1, the grain size of the ferrite grains in the starting material is large (~700 µm²) and the majority of grain boundaries is of high angle character.
This results in a fine grained microstructure consisting of (sub)grains at 1100°C.

The result shows that the alternating magnetism promotes the austenitic grain growth of low carbon steel.
Fig.1 Grain in air cooling after hot rolling Fig.2 Grain in austenite region by alternating Fig.3 Grain in ferrite region by magnetic after hot rolling alternating magnetic after hot rolling Seen from Figure 1, the fine grain size under air cooling after hot rolling is about 12μm (10 grades)，the grain is coarse and uneven.
After alternating magnetic under austenite region, the grain is recrystallization coarse and even(Figure 2), the grain saw being more blunt and pearlier is uniform.
After alternating magnetic radiating (1T), the properties of low carbon steel has a influence on the microstructure and austenitic grain tends to uniform and lower angle grain boundaries. 2.
In the tensile test, mechanical properties is in accordance with grain shape and size, the grain enlarge and mechanical properties decrease less.

This phenomenon strengthens with a further increase in the number of passes and the grain structure almost vanishes after the fourth pass: the grains appear in the form of parallel lines (Figs. 8d and 8e).
At the same time, porosity between the grains also changes, circular pores can be observed between the initial equi-axial grains, while part of them close and cease to exist with the number of passes, and while those remaining become elongated.
For a sintered sample this is 1 or a value close to 1 due to the initial equi-axial grain shape (the number of the horizontal and vertical sections is nearly identical).
In the case of grains becoming more and more elongated with an increase in the number of passes, the value of anisotropy decreases, for the horizontal number of sections decreases and the vertical increases (Figs. 1c and 8e), i.e. the value of the fraction tends to zero.
The grain structure of the deformed samples follows a directional structure identical to the direction of the deformation, and develops gradually with increasing the number of passes. 3.

The main reason for low ductility is associated with an insufficient number of deformation systems, activated at these temperatures due to the hexagonal crystal lattice type of the alloys with a high ratio c / a.
The average grain size also depends on the routes and modes of ECAP and generally decreases with increasing total strain due to increase in the number of passes.
Types of grain boundaries.
Grain refinement during ECAP is the result of activation of large shear deformation and dynamic recovery and recrystallization behavior, and with increasing of the number of passes low angle boundaries (LAGBs)of the formed small subgrains rotate relative to each other and adsorb a large number of dislocations, becoming the non-equilibrium high-angle grain boundaries (HAGBs)[10,11].
At relatively high temperature deformation of ECAP preferential formation of HAGBs can occur and at the small number of passes [12].

In the AA1100 alloy sheets, the grains were elongated along RD and the thickness of the elongated grains gradually decreased with increasing the number of ARB cycles.
Specimen Annealed 2 Passes 4 Passes 7 Passes 10 Passes 13 Passes Grain Thickness (µm) 35 4.5 1.8 1.1 0.5 0.45 Grain Length (µm) 33 14 6.1 3.4 1.3 1.1 In the sheet ARB processed by 2 cycles, a number of dislocations were generated in the original grains and it made subgrain structures.
The fraction of the UFG regions increased with increasing the number of ARB cycles, i.e. strain.
With increasing ARB cycles the grains were elongated along RD and the thickness of the grains gradually decreased
(2) The reduction of the grains thickness and length was carried out with increasing the number of ARB cycles, i.e. strain

studied carefully the hardness of the alloy during aging and revealed the existence of softer regions near the surface and the grain boundary than the interior of the grain even after aging for a long time [1].
Specimens for hardness test, 10x50x1mm 3, were strain annealed for the grains to grow to about 5mm in average diameter.
Fig.3 (a) shows the hardness number measured at 0.25 to 98N of load when the various thickness of surface layer was removed by electropolishing for the binary alloy specimen aged for 120ks at 293K after quenching from 623K.
When no surface layer is removed (as aged), hardness number decreases with decreasing load less than 9.8N.
If the specimen was homogeneous in hardness from the surface inward, hardness number would not show the dependence on the load, which has been confirmed by measuring a reference specimen [1].

With the increase of Fe-V, vanadium-rich carbides number increase, the grain size and hardness increase firstly then decrease above 2, at 20% gain the highest.
Vanadium has characteristics of improving solidification and refining the grain for improving crack resistance.
However, when Fe-V is very low, the grain size is thick and the direction of the columnar grain is remarkable, so the solidification cracks appear.
Effect of grain refinement is very obvious as increasing in Fe-V added content.
With the increase of Fe-V, the carbide phases number increase; the grain size and hardness increase firstly then decrease, at 20% gain the highest.

(3) where is the local free energy density, p is the number of lro parameters considered in a particular simulation, and ki and kc are the gradient coefficients which determine the width and the energy of the surface and grain boundary regions for a given f0 [15].
For simplicity, the diffusion coefficients have been assumed to be the same value within grains, e.g. , and grain boundaries in these simulations. p=36, according to Chen and Wang [17], such a number provides a reasonably good description of a polycrystalline microstructure.
Finally, in the region of these circles, the following values were assigned to the parameters: ,, i is a randomly natural number between 1 and 36, and c=1.
Then pore appears as black spots, grains are bright and grain boundaries gray.
Depending on the initial coordination number of the surrounding particles, the pores may have different shapes, as shown in Fig. 3(a) and (f).