Search results

The results showed that air-cooling cast strips have uniform and equiaxed grains with average size of 250 μm.
The microstructure of the water-spraying cast strips compose of most equiaxed grains and a small number of abnormal big grains.
Fig. 4 show respectively the grain size and texture of the cast strips which corresponding to Fig. 2.
As shown in Fig. 3, the size of most grains under water-cooling condition is smaller than that under air-cooling condition, while the cast microstructure under water-cooling condition has some abnormal big grains with diameter of 600-800 μm. as shown in Fig. 3b and Fig. 3d. it distributed the equiaxed grains containing straight grain boundary with average grain diameter of 210 μm along the rolling plane.
(2) The water-spraying cast microstructure becomes uneven, most of grains is smaller than that of the air-cooling cast strips, but some grains becomes bigger, and many of grains boundaries are bent

No austenite is observed at the prior austenite grain boundaries.
From these observations, the change in the number fraction of austenite grains formed at prior austenite grain boundaries is shown in Fig. 5 as a function of reversion treatment temperature.
The number fraction of austenite formed at prior austenite grain boundary is only a few percentages in the lower temperature region.
Figure 7 is the 100 Number fraction of reversed austenite grain formed at prior austenite grain boundary, N / % Reversion temperature, T / K 80 60 40 20 0 800 850 900 950 1000 600 550 650 700 Reversion temperature, T / ℃ T0 temperature Figure 5.
Effect of reversion temperature on fraction of reversed austenite grain formed at prior austenite grain boundary.

The sizes and number densities of dispersoids in at least 20 images from each homogenization condition were measured to ensure high accuracy.
It has been demonstrated that recrystallization and grain growth are inhibited when the migrating recrystallization front encounters a sufficient number of dispersoid particles, as a result of the Zener drag effect [12].
The number density of the dispersoid particles types decreases significantly with the increasing distance toward the grain boundaries.
It is clear that the sizes and number densities of the Zr-containing dispersoid particles change with the homogenization condition.
During homogenization at a given temperature, Figs. 6 (a) and (b), the sizes of dispersoid particles increase slightly, with time while the number density remain almost unchanged.

Development of initial structures similar to the real ones by simulating the grain-coarsening We began by developing a one-phase grain structure (Fig. 2.a) by using a simulation suitable for calculating the grain coarsening [6].
So-called smaller sub-grains could be developed by further grain-coarsening (Fig. 2.b) in these grains by modifying the simulation.
The boundaries of the earlier grains indicate the former grain boundaries of austenite while the boundaries of the above smaller grains indicate the boundaries of pearlite colonies.
b) a) Fig. 2. a, b Grain structures developed by the simulation of grain coarsening (a, one-phase grain structure, b, sub-grains in the previous structure) The ferritic-pearlitic initial structures are developed from these pearlitic structures in such a way that the former austenite grain boundaries „are thickened” after the second step so the proeutectoid ferrite can be obtained (Fig. 4).
The cementite balls with different sizes and numbers were drawn in this ferritic matrix by the software.

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 grain size is computed assuming the grains to be circular and calculating diameter from the circular grain area.
When the average grain size enlarges and the uniformity of the grain size distribution is improved in Cu lines, the number of grain boundaries and the fraction of triple junctions will reduce, respectively.
We can conclude that the number of grain boundaries in Cu lines with trench aspect ratio of 0.068 and the fraction of triple junctions in Cu lines with trench aspect ratio of 0.176 is the minimum.
Therefore, the number of grain boundaries in Cu lines with line spacing of 1.81 mm and the fraction of triple junctions in Cu lines with line spacing of 0.19 mm is the maximum.
Since Σ3 grain boundaries are twin grain boundaries as well as Σ9 grain boundaries are the twin variant grain boundaries, so it is also easy to exist in annealed Cu lines and Cu blanket films.

The analysis result can be known that the atomic number ratio of Mg and Al was 17:12, and little zinc was melted in it from Fig4 (b), which is consistent with β-Mg 17Al12, therefor spectrum1 is β-Mg 17Al12.
The number of dimples with irregular shape gradually increases.
During the deformation of the UCAP, the mechanism of grain refinement can be attributed to the shear action of the extruded angle inducing grain net changing, and the grain crushing caused by the slip deformation of the prismatic plane and compression deformation process, and the continuously dynamic recovery and recrystallization occurred during the entire UCAP deformation; Under the shear stress, a number of plastic deformation are introduced through constant deformation, and dislocations are produced and accumulated in grains especially coarse grains, and dislocation network are continuously formed.
Finally, the large angle grain boundary migrates, and part of the grain and sub grain boundary is eliminated, then obtain fine recrystallized grains.
We know that the recrystallization is suitable for occurring in defect density higher place, a large number of crystal nucleus are produced in the high energy region of severely crystal lactic distortion, the new grains grow up in the boundary of recrystallization grain, so that through the recrystallization and dislocation rearrangement formed by large angle grain the magnesium alloy grain is refined.

The fluid effect is attributed to the number of active abrasives, but the effects of slurry particles under hydrodynamic contact were not investigated.
Recently, Jeng and Tsai presented and discussed the mathematical formulae for grain/grain collision elasticity, grain size and roughness [23-24].
That is, increasing kw implies the grain-grain collision is becoming more inelastic and makes the energy loss larger.
Our prior works have discussed the effect of grain-grain collision elasticity on the flow factors.
grain/grain collision elasticity, particle size and pad asperity.

In contrast, in 3rd and 4th passes of rolling new grains nucleated at grain boundaries, due to low grain size of the alloy.
Because of their low formability due to the limited number of available slip system, the forming and shaping of wrought magnesium alloys at room temperature has been highly restricted.
Although the average grain size increased during heating the specimen, the grain size of the alloy reduced with the increase of the number of rolling passes.
In the beginning of the hot rolling process, mechanical twinning occurs easily inside the grains, because of large grain size.
In last two samples, mostly new grains nucleated at primary grain boundaries forming equiaxed grains.

For a polycrystalline structure, the grains are deformed by crystallographic sliding located in the most favorably oriented systems and which support a strong constrained stress . 1.
Volume fraction of grain.
Its microstructure (number and orientation of grains) can be determined by using Euler angles defining the orientation of each grain.
From now on this study can be generalized to other model of the mechanics of the materials and especially for models having a large number of parameters.
A note on Guttman’s lower bound for the number of common factors.