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The CR 7075 Al alloy shows improved fracture toughness and tensile strength due to high dislocation density, grain refinement, and ultrafine-grain (UFG) formation by multiple cryorolling passes.
The microstructure of the bulk alloy exhibits lamellar grains having average grain size around 40m, lying parallel to the ingot axis.
Since the dynamic recovery is effectively suppressed by rolling at cryogenic temperature (-190oC), the CR Al 7075 alloy shows high amount of dislocation cells and ultrafine grains or grain fragments.
(1) Where, = Constant (Mpa m1/2), d= Grain size.
Dislocation piled up in the grain boundary, during cryorolling, rearrange themselves, and form sub grains.

It was observed that the grain sizes increases appreciably.
It is important to note that grain characteristics are controlled to produce different mechanical properties.
Generally, the faster the cooling rate, the refined and smaller the grain sizes will be but in this instance, the rate of cooling was kept constant but varied the number of scan irradiation and the laser power.
Table : Measured grains of the parent and the LBF components No.
The number of scan irradiation being the number of time the laser passes on the surface of the component.

The increase in number density and volume fraction are associated with precipitation of new particles.
The low magnification image shows constituent particles decorating the boundaries of a grain.
Within the grain, the dispersoids can be seen to have precipitated, with a relatively wide dispersoid free zone adjacent to the grain boundaries.
Figure 5 (a) shows the predicted number of excess vacancies (introduced by deformation) relative to the number of thermal vacancies and the predicted dislocation density as a function of strain rate at 500�C.
Above a strain rate of approximately two, the number of deformation induced vacancies is predicted to exceed the number of thermal vacancies.

The grain refinement was assisted by the development of deformation twinning.
An early warm deformation leads to the elongation of original grains along the rolling direction (RD) and the development of large strain gradients within the grains.
At a maximum total strain (e=3), the deformation structure is composed of highly flattened austenite grains with transverse grain size of about 220 nm (Table 1).
The grain refinement was assisted by the deformation twinning, which resulted in rapid grain subdivision at relatively small strains, followed by shear banding.
Acknowledgements The financial support received from the Ministry of Education and Science, Russia, under Grant No. 14.575.21.0092 (ID number RFMEFI57514X0092) is gratefully acknowledged.

The coercivity decreased as the number of precipitate decreased and the width of martensite lath increased.
However, some experimental investigations reported the effect of grain boundaries on the magnetic properties.
The magnetic coercivity versus the inverse of the width of martensite lath and number of precipitates.
Degauque et al. [12] noticed that the magnetic coercivity was inversely proportional to the grain size in high-purity iron and they insisted that the grain boundaries could be obstacles to the movement of the domain wall.
Takahashi et al. [13] also showed that the magnetic coercivity was inversely proportional to the grain size in α-Fe metal.

The basal texture is enhanced during sintering by selective anisotropic grain growth.
The increasing number of papers, based on this methodology, illustrates the interest of many researchers in materials science for Rietveld texture analysis [13-17].
As mentioned above, the number of points results from a selection with a criteria of confidence index (CI>0.01), in order to optimize the accuracy of the indexing selection.
However, while about 3×109 grains were involved in the neutron analysis, EBSD measurements on the polished surface covered at most 10000 grains.
Further experiments must however be performed for increasing the number of points and improving the accuracy of the analysis.

The processing routes exert a strong influence on the development of the ultra-fine grain structure [5,6,10-12].
rationalized the effect of the processing route in terms of crystallography; when a billet was rotated in order for a slip plane to be inclined close to the grain elongation direction or theoretical shear plane, the grain fragmentation was promoted [13].
Slip pattern analysis suggested that a large number of slip systems were activated, resulting in the formation of deformation bands as observed macroscopically.
In route A, however, microstructures are still layered structures with dislocation boundaries closely parallel to the grain elongation direction, while those in route Bc are more equiaxed structures with grain diameter less than 500 nm.
It is suggested that these heterogeneous structure might promote the grain refinement in the subsequent passes.

The higher Fc value, the more round of the α-Al grain is.
As seen from Fig. 2(a), the α-A1 primary grains in the sample were not of uniform size and the fine grained regions were detected.
As seen from Fig. 2(b), the distribution of α-A1 primary grains in the sample were uniform and the average grain size was 38µm with the casting temperature up to 740℃.
Temperature(℃) Temperature(℃) Fig. 3 The relationships of the average grain size and the average equivalent roundness of the squeeze-cast Al-Zn-Mg-Cu alloy with the casting temperature According to the thermodynamics law, the nucleation in molten metal is more and more difficult and the crystal nucleus number which can be kept is less and less with the increasing physics heat supplied by melt temperature.
The grain size constantly decreased with the increasing Al-10RE refiner.

The microstructure with coarse carbides and large grains reached greater loss of impact toughness [9].
The number of particles per µm2 was calculated by counting the precipitates and their diameter was directly measured.
The fractographic analysis revealed the presence of two types of particles precipitated within the fracture surface [11], which were intergranular, i.e., along the grain boundaries, and transgranular across the grains.
Substitute pin showed a larger transgranular particle density value compared to that of the original pin, which was related to a greater number of particles precipitated.
The original pin showed medium size, nearly rounded particles (Fig. 6a), which exhibited preferential transgranular precipitation, i.e., across the grains, followed by the intergranular precipitation (among grain boundaries).

Structural-Phase State of the Interphase Boundary at Thermal Diffusion Metallization of Diamond Grains by Cr and Ti P.P.
Metal powder Grain size [μm] Chromium 3-5 Titanium 120-125 In order to study the microstructure, morphology, the chemical composition of the metallized diamond grains and the diamond-coating interphase boundary, the scanning electron microscopy (SEM), X-ray spectroscopy and diffraction methods were used.
The numbers on the images indicate the points where the chemical composition of the coating was measured by the Energy-dispersive X-ray spectroscopy (EDX) method.
Whereas, the coating metallized by titanium has a layered and non-uniform in grain size and homogeneous in elemental composition structure.
Agren, Sintering shrinkage of WC-Co materials with bimodal grain size distribution, Acta Materialia. 53 (2005) 1665–1671