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MC(2) carbide and γ' phase in the grain boundary form chain along grain boundary, and effectively retard grain boundary sliding. γ+γ' eutectic is basically eliminated by solution treatment and only a little γ+γ' eutectic exists around carbide.
During subsequent low temperature ageing of 870℃/20h, the primary γ' phase further grows into regular cuboidal with the size of 0.4 µm and the number of secondary γ' phase is dwindled because the solute elements in the secondary γ' phase, which were consumed for the precipitation and growth of the primary γ' phase, diffuse to around the larger primary γ' phase, and the uniformity of alloy composition is further increased.
The MC(2) carbide and γ' phase in the grain boundary distribute in chain-like along grain boundary( see Fig. 3).
Fig. 2 Carbide morphologies at different directional solidification rates after heat treatment： (a) V=50μm/s; (b) V=100μm/s; (c) V=255μm/s; (d) V=500μm/s; (e) V=800μm/s Table 2 Composition (wt %) of different MC(2)carbide after heat treatment Elements Ni Co Cr Ti Al Mo Ta Hf W Blocky carbide 3.61 1.02 0.6174 0.6047 0 0.651 28.7 53.15 9.75 Chinese-script carbide 4.3 1.3 0.7076 1.08 0.0148 1.1 32.7 45.38 11.69 Fig. 3 Morphology of carbide in the grain boundary after heat treatment (V=100 μm/s) γ+γ' eutectic after heat treatment.
The MC(2) carbide and γ' phase in the grain boundary distributed in chain-like along grain boundary. γ+γ' eutectic was almost dissolved other than in very small amounts around carbide.

To get good properties, we need to have at least 10 grains per foil thickness.
Can we not invent a new hybrid process that will increase the number of grains to at least 10 grains per foil thickness?
The deviation was from 10 to 2%, depending on the number of passes.
The more the number of passes, the less the deviation.
It is well known that shear strain plays a critical role in the grain refinement.

In comparison with Fig.2(b), W are wrapped by Cu along the W grain boundary, and two phases are distributed homogenously.
La addition changes the morphology and distribution of impurities among W grains and densifies W skeleton.
For the infiltrated WCu alloy, its properties mainly depend on the porosity and grain size.
These are beneficial to eliminate their disseverment to the grain boundary, and hinder the movement of grain boundary or subgrain boundary.
On the other hand, the grain refinement increases the number of grain boundary, thus enhancing the electron scatter and decreasing the electrical conductivity.

A number of previous researches about the Inconel 718 superalloy grinding have been carried out to investigate the correlation of forces, temperature and power during the grinding process, wheel wear condition and final workpiece quality with grinding parameters [5,6].
Moreover, in order to establish the correlation of grain failure patterns with the measured power to predict wheel wear condition, cBN grains on the wheel surface are observed by FEI Quanta 200 FEG Environmental Scanning Electron Microscope (ESEM) to identify different wheel wear conditions.
When the wheel goes into the re-sharpening stage, new cBN grain or cutting edges emerges due to old grain worn-out or grain breakage as in Fig. 6(d).
Therefore, the growth rate decrease, which is shown at the third stage in Fig. 5, result from the higher cutting efficiency of new cBN grains.
When the grinding wheel goes into the severe stage, the surface roughness drops dramatically, as the number of grains contacting with the workpiece increases and forms smoother surface.

For comparison, the number fractions of the small angle grain boundaries for all annealed tapes calculated by orientation image micrography (OIM) software were plotted together in Fig. 3.
The fraction of the small angle grain boundaries in the tapes annealed in flowing gas is higher than that of the tape annealed in vacuum.
It is worthwhile to note that no twin boundaries were observed in the TSA tape, where the grain sizes are smaller.
It is supposed that the first step annealing at lower temperature increases the number of nuclei of cube oriented grains, suppressing the random orientation nuclei which are always occurred during one step annealing at higher temperature.
On the other hand, the second step annealing at higher temperature is of benefit to the further growth of cube textured grains [8].

Both mechanisms result in improved mechanical properties due to grain size refinement of the transformed ferrite.
Since both grain boundaries and deformation bands act as nucleation sites for the austenite-ferrite transformation and since the austenite grain elongation means that the grain boundaries are getting closer to each other, it is obvious that the deformation below Tnr increases the nucleation density.
The first mechanism is the so-called solute drag effect [3,4] by which elements in solid solution interact with the grain boundaries so that they decrease the grain boundary mobility and thus the recrystallization rate.
Another big difference might be due to the grain size at 900°C deformation temperature.
At this temperature, the torsion test sample has already undergone a large number of deformation passes and a large amount of total deformation.

The casting materials had grain-shaped structure when they reached to 585℃ which is an eutectic temperature in this alloy.
In semi-solid region, the structure of the torsion working material was finer than that of casting material and became a more grain-shaped structure.
However the torsion working material was remained grain-shaped structure. 1.
γ＝nrπ/L (1) Where n, γ, and L are number of rotation, radius and gauge length, respectively.
Grain shaped crystals become finer and more granular with increasing the amount of strain.

SEM imagines exhibits that the grains of the products become larger with increasing N2 pressures.
SHS technique has been effectively applied to produce a number of the MAX carbides, like Ti3SiC2 [8], Ti3AlC2 [9] and Ti2AlC [10].
Typical layered grains of Ti2AlN can be seen in Fig.4.
With increasing N2 pressure, the grains of the products significantly grow up.
The grains of the products become larger with increasing N2 pressures.

The film was composed of inverted triangular-based pyramidal grains (T-grains) and inverted diamond-based pyramidal grains (D-grains).
The number of the T-grains is much greater than that of the D-grains in the present specimen.
Fig. 5 Plan-view TEM image of YSZ grains aligned in the <111> (T-grains) and SAD pattern taken from the grain indicated by A.
Fig. 7(a) Plan-view TEM image of YSZ grain aligned in the <110> (D-grain) and SAD pattern.
(b) YSZ grain slightly tilted along the <110> axis from the grain in (a).

These rocks comprise of grains predominantly with quartz content besides Plagioclase-albite, Feldspar, lithic fragments.
The proportion of grain contact controls both strength and deformability [9]. 3.2.
In control mix and up to 30% voids developed on the boundaries of aggregates were less in number, while at 50% &100% replacement micro-cracks were developed at the margins of few voids.
The compressive mechanical behaviour of the material influenced by porosity & particularly Porosimetry distribution & high number of micro-cracks, pores & voids contribute to higher initial deformations [21] Figure 5.
Textural maturity indicates the high quartz content with grains type are moderately to well sorted and comprises shape of sub angular to sub rounded which indicate better inter-particle packing, sorting and rounding of grains with less sensitive to environment.