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As a large number of surface monoclinic phase was generated, due to there are a lot of microscopic defects in the phase transition layer, crystals loose, strength of grain boundary lower than that of not aging area and phase transformation layers fracture in the intergranular mode, that damages the flexural strength.
It can be seen that grains in phase transformation region are clear and strong three-dimensional sense, while grains in no phase transformation region is fuzzy.
At the same time, there are a large number of micro-cracks and other defects in the t-m phase transformation layer in surface, which makes flexural strength decrease.
Because there are a large number of defects in phase transformation layer, the flexural strength is lower than that of no phase transformation part.
As a large number of surface monoclinic phase was generated, due to there are a lot of microscopic defects in the phase transition layer, crystals loose, strength of grain boundary lower than that of not aging area and phase transformation layers fracture in the intergranular mode, that damages the flexural strength.

Materials processed by SPD show not only unique physical and mechanical properties inherent in various ultrafine grained materials, such as high strength and superplasticity, but also a number of advantages, such as less grain growth and contamination, over nanostructured materials manufactured by other methods through powder processing.
The present authors envisage that ECAP would be effective in matrix grain refinements as well as enhancing matrix-particle bonding.
Agglomerates of CNTs and pores were found in many places by EDX analyses after 1 pass, and the separations of the CNT agglomerates and the homogeneous distribution of CNTs were achieved with the number of ECAP passes.
The decreases in matrix grain size and inter particle spacing increase strength and strain hardening of the composite by decreasing dislocation mean free paths.
Cu sheath CNT/Cu powder P-ECAP Sample 1 2 3 4 5 6 7 8 40 60 80 100 120 140 Initial Cu Hardness, HV Number of ECAP Passes 5 vol% CNT/Cu Composite Fig. 4 Hardness with the number of ECAP passes.

To describe the corrosion morphology, two parameters were statistically determined: the number of corrosion defects propagating in the L direction and observed for a given distance in the ST direction (density of corrosion defects) and the average depth of corrosion defects in the L direction.
Taking into account the cumulated length of corroded surface observed in the ST direction, i.e. 80 mm, and the grain size in this direction (about 60 μm), almost 1000 grain boundaries and grains were observed for each test.
When the NHT samples were aged, the density and size of T1 precipitates in the grain boundaries increased but numerous T1 precipitates also formed inside the grains.
The galvanic coupling effect between the grains and the grain boundaries was reduced so that intergranular corrosion did not occur.
Fig. 3c suggested that the branching could be attributed to both an extent of the corrosion to a larger number of grain boundaries but also to the dissolution of subgrain boundaries.

Grains modelling.
Fig.1 shows the results of the computational homogenization for BaTiO3 performed by computing volume averages of the micro-fields over aggregates containing different numbers of grains.
Fifty morphologically different random realizations are generated for each selected number of grains, which are assigned random spatial crystallographic orientation.
For each realization the volume averaged values of the apparent shear modulus and relative dielectric constant are plotted versus the number of grains in the aggregate; ensemble averages are also shown.
Moreover, since only meshing of the grain boundaries is required, simplification in data preparation and reduction in the number of DoFs are attained, with consequential computational benefits.

The parent alloy casting sample was an equiaxed structure with a grain size of 15–60 μm and contained a large number of eutectic phases at the grain boundary (Fig. 3(a) and (b)).
According to Figure 4(a), the master alloy casting sample is an equiaxed structure, and there are a large number of skeletal eutectic phases at the grain boundary with a width of ~2–10 μm, which are evenly distributed along the grain boundary.
From Figures 5(a) and (c) and the energy spectrum analysis, a large number of Al3Ti phases (needle-like and with a massive structure) and TiC phases (granular) are distributed in the alloy casting, and the grain size is between 10 and 200 μm.
Acknowledgments Foundation item: This work was supported by the National Natural Science Foundation Project [number 51661031; 51861033].
Microstructure and formation mechanism of grain-refining particles in Al-Ti-C-RE grain refiners[J].

Journal Title and Volume Number (to be inserted by the publisher) 3 Steel C Si Mn P S Cr Al N Nb Ti DIN EN 10084 0,14 - 0,19 ≤ 0,40 1,00 - 1,30 ≤0,035 ≤0,035 0,80 - 1,10 - - - - 16MnCr5+Nb 0,19 0,23 0,74 0,011 0,012 1,19 0,041 0,026 0,045 0,001 Table 1 Chemical composition of the investigated steel, mass content in %.
This gives improved grain size stability at higher temperatures that has been confirmed by grain growth investigations.
The grain size distribution is given by means of the cumulative frequency of grains belonging to different ASTM classes; the approximate average grain size is represented by the 50% cumulative frequency.
Figure 4 Calculated nitride and carbide precipitates. 700 600 500 400 300 200 100 0 700 600 500 400 300 200 100 0 NbC NbN TiN AlN 1000 1200 1100 Temperature, °C Mass fraction of precipitates, ppm Journal Title and Volume Number (to be inserted by the publisher) 5 ening temperature (GCT) is associated to the following limit in this investigation: all grains must be of ASTM size 5 or finer; grains of ASTM size classes 4 and 3 are tolerated up to a total volume fraction of 10%; grains of ASTM size class 2 or coarser are not permissible [6/10].
The grain size stability at elevated temperatures is attributed to a sufficient amount of precipitates which guaranty a grain boundary pinning.

INFLUENCE OF TEMPERATURE AND HOLDING TIME ON NUMBER AND SIZE OF METAL PARTICLES DURING SOLID-PHASE REDUCTION OF IRON BY CARBON A.
Relatively large nuclei are formed on the surface of the ore grains; first in the form of a non-continuous shell and in a slightly changed internal volume of grains, and second in the form of small metal phase forming separate lines [2].
These phases (metal and slag) appear on the surface of the initial grains of titanomagnetite, as well as along the boundaries of the crystallographic blocks inside the initial grain of titanomagnetite [5, 6] and crush the original grain into smaller particles [7, 8-12].
A total number of 1439 fields of view were examined and 542483 iron particles were detected.
The average number of reduced metal particles at temperatures of 1300, 1500 and 1600 °C varied from 252 to 407.

It can be seen that the number of cleavage planes of Alloy Ⅰ is higher than Alloy Ⅱ.
However, the number of dimples shows the opposite trend.
The curves of crack length versus the number of cycles (a-N curves) are presented in Fig. 3(b).
It can be seen from Fig. 5(a, c) that fine recrystallized grains ( the green part in the picture ) are scattered in the alloy and the number is small.
In general, the FCP rate is smaller for alloys with coarse grain size than for those with fine grain size.

For a number of alloys based on titanium nickelide the effect of SRQ on the internal structure, grain refinement, and amorphization has been considered.
The number of such orientations can be only 12.
First crystals that have appeared in the grain of an initial phase determine in a considerable extent the further course of MT not only in the given but also in adjacent grains.
Crystallographic texture is provided via employing quite a number of ways [6-11].
Employment of several passes by different optimum technological routes made it possible to create in these alloys the nano-structure highly uniform uni- or bi-modal grain–subgrain state with average grain sizes close in value to 100–200 nm (Fig. 21).

Optimum Pass Design of Bar Rolling for Producing Bulk Ultrafine-grained Steel by Numerical Simulation Tadanobu Inoue National Institute for Materials Science, 1-2-1, Sengen, Tsukuba, 305-0047, Japan INOUE.Tadanobu@nims.go.jp Keywords: Rolling, groove design, finite element analysis, ultrafine-grained structure, strain distribution, low-carbon steel Abstract.
The groove design for creating ultrafine-grained low-carbon steel through a caliber rolling process was studied from the viewpoint of the large strain accumulation and cross-sectional shape variation in a bar.
The optimum pass schedule to fabricate a 13mm square bar of ultrafine-grained steel from a 24 mm square bar by caliber rolling at warm working temperatures was proposed.
Introduction Refinement of crystal grains is an effective method for developing toughness and strength in steels without the addition of alloying elements by controlling the thermomechanical treatment.
Since a large strain is needed for creating ultrafine-grained (UFG) structures, various severe plastic deformation processes have been proposed [1].