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Effect of various numbers of passes through ECAP (Equal Chanel Angular Pressing) die on microstructure and properties have been evaluated.
It is clearly seen effect of improving both yield stress Re as well as tensile strength Rm with number of passes through the ECAP die.
It is also seen the positive effect number of passes through on the grain size that decrease more twice after two passes through.
Microstructure investigation were carry out only using light microscopy as the grain size of the cast was quit large (corresponds grain size number G0) and it is documented both for virgin state and for ECAP samples in the Fig. 4 and Fig. 5.
Change in the grain size can be also expressed using Grain size number according to ASTM E 112 that changed from G0 for cast state to G2.5 – G3 after two passes through, it means refining about 50 %.

Effect of Casting Temperature on Grain Size of Al-Si Alloys Refined by a Novel Grain Refiner L.
After the addition of the NGR (Figure 4 b), not only the size of the primary α-Al dendrites is significantly reduced but the mean length of the eutectic phase and the size and number of primary silicon particles present in the microstructure is reduced as well.
Moreover, the presence of a much bigger number of dendrites growing is favouring the nucleation of the eutectic phase due to the fact that the lattice mismatch between them is rather small. 4.
John, Grain Refinement of Aluminum Alloys: Part I.
Bolzoni, Grain Refiner for Al-Si Alloys, Light Metals, (2013) 1009-1012

Recent research has shown an interest in this method, which can be declared with an increasing number of scientific publications or patent activities on this issue [1-10].
These measurements were supplemented by the measurement of changes in the speed of the longitudinal ultrasonic wave UZvl in the realized number of Nextr = 6.
The greater the grain size of the structure, the greater the irregularity and randomness in grain distribution and vice versa.
Grain distribution according to equivalent hekv depth.
However, it should be noted that in the system of our calculation methodology, the parameter h does not represent a single parameter variable, but is in mutual functions to a number of other parameters in the process.

This grain element is connected by grain boundary element to account for shear deformation between grains.
This grain element is connected by grain boundary element to account for shear deformation between grains [8].
Grain Boundary Element.
In FE model, the numbers of grain element and grain boundary element are 910EA and 1132EA, respectively.
Grain element is used to analyze the deformation of individual grains while grain boundary element is for observing the sliding, extension and grain boundary effect.

The process of plastic deformation in ultrafine grain titanium is considered.
A single diffraction peak (main reflex) or a number of diffraction maxima (subreflexes) would arise in the same area according to whether the material of the crystal has an ideal structure or is composed of individual crystalline blocks separated by low-angle boundaries.
A number of factors determine the angular resolution of the method: (i) the quality of a focused beam of X-rays, depending on emitter type and monochromator performance; (ii) the angle of reflexion and (iii) the extent of misorientation of crystallite blocks.
It can be seen from the histogram in Fig. 3 that subgrains and grains having sizes 0.1…0.4 μm account for 80% and non-equiaxial subgrains and grains having sizes 0.6…0.9 μm, the remaining 20%.
Fold-like meso-defects characteristic for ultrafine grain metals will form within the high-amplitude zone; the ultrafine grain structure of metal is characterized by the occurrence of non-equiaxed subgrains, which are elongated along the sample extension axis.

With reference to the characteristics of polycrystalline materials, according to contemporary terminology UFG materials may be defined as polycrystals having very small grains with average grain sizes less than ~1 mm [1].
Mechanical properties of steel AISI 321 and structure parameters after HTMP with different numbers of passes n and different rolling reduction, e.
The volume density of the precipitates increases and their size decreases up to 0,1 mm as the number of passes increases.
Langdon, Twenty-five years of ultrafine-grained materials: Achieving Exceptional properties through grain refinement.
Micro-Mechanical Responses of Ultrafine-Grained Materials Processed through High-Pressure Torsion.

When the grain size is sufficiently small and dislocation-dislocation interactions and then workhardening is improbable, dislocations most likely interact with grain boundaries.
Compared to the first series, the relaxations depend on the relaxation number and on the strain history.
The apparent activation volume, * vΩ , increases with the relaxation number from about 30 3b to 40 3b , which indicates a transient domain with variation in dislocations density.
Slop at t=0 of the relative dislocations density as a function of the relaxation number.
This value is relevant regarding the fact that the fine grained copper is ductile and pile-up effect is observed at the indent.

The dynamic evolution of grain growth in the process of aluminum casting and the impact of different casting conditions on the grain growth were simulated by using the Cellular Automation(CA) method in this paper.
A computer was used to simulate microstructure formation of aluminum in the grain scale.
Based on the above considerations, in this paper, the CA method was used to simulate the grain growth in the solidification process of aluminum casting and the effect of the process parameters on grain growth.
(8) As, a unitary quadratic equation about can be got as below: (9) Where: is the diffusion coefficient of solute, , is the growth velocity of dendrite tip, is the slope of liquidus, is the compositionally gradient of interface, is the function of Peclet number, is the average temperature gradient, is the stability constant, ,is the Gibbs-Thomson coefficient, is the ingredients undercooling, is the curvature undercooling, is the thermal undercooling, is the kinetics undercooling, is the solute partition coefficient, is surface energy,is volume melting entropy, is the Peclet number of solute, is the Ivantsov function of Peclet number, ,, is the initial concentration of the alloy, is the solute partition coefficient,is the growing radius of dendrite tip.
The dynamic growth of grain shows as Fig.2.

EBSD method is effective to measure the orientation relationships since it is easy to calculate localized textures and to obtain the statistical satisfactory analyses with Goss grains populating with significantly low number in the primary recrystallization matrix.
The mean grain diameters and frequencies of these grains were shown in Table 1.
The orientations of over 1000 grains surrounding Goss grains were measured to achieve the statistically satisfactory analysis, as well as {311}<011> grains.
It is supposed that Goss grains grow more preferentially than the other candidate grains due to the highest Σ9 frequency at the commencement of the grain growth.
Σ1 and Σ3 frequencies were higher around {311}<011> grains than Goss grains.

TEM image of the two kinds of precipitates in as-rolled tested steel A great number of precipitates, see Fig.1, which appear to be nearly rectangular or spherical, in tested as-rolled microalloyed steel were revealed under TEM.
As seen from the Fig.4(a), the finer austenite grains distribute inhomogeneously as new austenite grains contact with each other and the grain boundary is bent.
Under the temperature of 1100℃, the average grain size of austenite is less than 50μm; from 1100℃ to 1270℃, the grain size grows up gradually; at the temperature above 1270℃, the grain size increases rapidly.
However, under the same condition, effect of holding time on the grain size is less obvious than heating temperatures on the grain size of austenite.
Consequently, the grain size increases tremendously.