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The microstructure was effectively refined with increasing the number of CEC cycles as the grain size was reduced from ≈250µm to ≈30 µm after 6 cycles of CEC.
Microstructure Analysis Coarse equiaxed grains with ≈250 µm grain size were observed in annealed specimen, Fig.3, which represents the initial condition samples for CEC.
With increasing the number of cycles the macrohardness increased with a lower rate up to 6 cycles reaching about 2 times the hardness of the annealed alloy.
The improvement of the hardness value of the CECed samples is mainly due to the grain refining and work hardening in the material with increasing the number of cycles.
Summary · As the number of CEC cycles increases a more homogeneous grain structure with reduction in grain size from 250 µm to 25 µm

Cold rolling flattens the original grains.
As there is no significant increase in the total number of particles, the solute is precipitated at already existing particles and their coarsening takes place.
The non-homogenised alloy, SV97, contains a number density of dispersoids that is five times greater than that in the homogenised SH97, which should give an appreciably higher Zener drag on moving grain boundaries.
These circumstances together with the observed similarity in the kinetics of precipitation and grain growth and the relative constancy in the volume fraction and number of dispersoids suggest that the precipitation of Mn during subgrain growth takes place by boundary diffusion to existing precipitates.
A pre-requisite for continuous grain growth to occur in these alloys is that the amount of cold work before annealing should be very high, which creates a large number of HAGBs.

Introduction It is well known that grain refinement improves both strength and toughness simultaneously in polycrystalline materials.
So, the number of nuclei for recrystallization [4] is larger in the reversed austenite than the original austenite, resulting in the smaller recrystallized austenite grain size in the initial martensite structure.
(2) The recrystallized austenite grain size is much smaller in the start structure of martensite than the original austenite
Mould: Recrystallization and Grain growth in Metals (A Haisted Press book, 1976), p. 62 20 30 40 50 60 70 80 90 10 20 30 40 50 60 70 original austenite martensite Grain size (§-) Reduction of thickness (%) Fig. 6 Relation between the recrystallized austenite grain size and the initial hardness for the two structures of Fe32%Ni alloy.
Fig. 5 Relation between recrystallized austenite grain size and reduction of thickness in the two start structures of Fe32%Ni alloy. 58 59 60 61 62 63 64 65 66 67 10 20 30 40 50 60 70 Grain size (§-) Hardness (HR-15N) Original austenite Martensite

The number density of platelike particle was low and the surface of particles was curved.
The condition for the preferential growth of template grains at the expense of matrix grains was lost at this stage.
Template grains in Na-excess specimen (side view). they were formed from one BiT grains.
Therefore, the number density of platelike grains was low, resulting in the small degree of orientation in the sintered compacts.
In the Na-deficient specimen, on the other hand, the coalescence of small grains in the skeleton particles was not so extensive, resulting in a low number density of template particles and a small degree of orientation.

Finer equiaxed grains can also help improve castability and thus grain refinement is a critical step in the microstructural design of many alloy castings.
There are several ways of producing finer grains in alloy castings but grain refinement using inoculants is the preferred route.
Observations reveal that although a large number of inoculant particles are added greater than 90% do not take part in the grain refinement process [3-5] indicating that not only is size important but that another factor is limiting a master alloy’s effectiveness.
Greer, Grain refinement of alloys by inoculation of melts, Phil.
StJohn, An analysis of the relationship between grain size, solute content, and the potency and number density of nucleant particles.

As the temperature is above recrystallization, some small cracks (or voids) formed along grain boundaries and slip deformation took place in many coarsened grains, while only extrusions and intrusions instead of obvious cracks or voids are observable for UFG Ti.
Experimental Procedures The UFG Ti and Cu rods with an average grain size of ~250 nm were produced by ECAP.
Simultaneously, some small cracks (or voids) initiated along grain boundaries (GBs) and slip deformation took place in many coarsened grains, as indicated in Fig. 1(c).
Analogously, the microstructures of compressed UFG Ti exhibited a somewhat decreased number of GBs than its initial states [10].
Notably abnormal growth of many grains occurred and the maximum grain size has got to more than 2 mm.

The process parameters of ECAP (Channel Angle, angle of curvature, friction, number of passes, etc) influences major impact on the properties.
In all the above methods, the grain refinement to nano-scale grain structure in the bulk material is achieved by applying a severe plastic deformation.
Researchers have demonstrated a number of theoretical and experimental analysis on ECAP process [5-10], Fig. 1, to study the effect of process parameters on material behaviour.
Figure 6: Variation of MicroHardness with number of passes Figure 7: Variation of UTS with number of passes Tensile properties evaluated upto 2 passes of ECAP is depicted in Fig. 7.
Langdon, Ultrafine-Grained Materials: a Personal Perspective, J.

Route A has no rotation of the sample, route BA is rotated counter clockwise 90° on even number of passes and clockwise 90° on odd number of passes, route BC is rotated counter clockwise 90° after every pass (see Fig. 1b.), and route C is rotated 180° after every pass [9].
Increasing the number of passes (the accumulated equivalent strain), secondary phase particle size decreases, its distribution becomes more uniform, and also the grain size of 6063-T1 alloy is more refined.
It was determined that for the unprocessed aluminum alloy, the microstructure shows coarse dendritic grains, with a secondary phase at grain boundaries (specific continuous casting structure).
Increasing the number of passes, secondary phase particle size decreases and its distribution becomes more uniform and also the material grain size is more refined.
Butu, Mechanical behavior and microstructural development of 6063-T1 aluminum alloy processed by equal-channel angular pressing (ECAP): pass number influence, JOM, 64 (2012) 607-614

The effect of thickness and grain size on the scattering was discussed.
thickness in the case of specimen with different grain size.
Many grains exist in the through-the-thickness direction when grain size is very small, so the variation in crack growth resistance becomes small.
Thus, it is demonstrated that the error of estimated cyclic number is small and the measurement accuracy is improved using specimen with small grain size such as ED Cu for smart patch.
(3) The error of estimated cyclic number was reduced using specimen with small grain size such as ED Cu for smart patch.

On the grain scale, the Schmid coupling between the stress tensor and the distribution of crystallographic orientations provides a grain-by-grain distribution in strain.
The number of nuclei per element is computed via Eq. (3) using the local strain at that element, and nuclei are placed in the element.
Journal Title and Volume Number (to be inserted by the publisher) 5 Figure 3.
For e = 0.3, the distribution are similar; however, the nonuniform system has a larger number of very small grains, due to the clustering of nuclei and their subsequent growth impingement in high strain regions.
While both uniform and nonuniform microstructures are quite fine-grained, the nonuniform system contains a significant number of larger grains, which result from nuclei growing in to the low-strain, low-nuclei regions of the microstructure.