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The creep mechanism of the composite is dislocation and grain boundary sliding control.
The current study results of magnesium alloy creep show that their creep deformation mechanism is dislocation slip mode and grain boundary sliding mode[9].
The non-continuous precipitation organizations make the movement and slip of the grain boundary be able to be carried out easily; while the movement and slip of the grain boundary carry through the form of dislocations, the creep fracture surface of the specimen must have obvious steps.
At a high temperature, plastic deformation of the matrix should be evident, that is, there exists a large number of dimples; and the fracture surface with clear micro-cracks.
In the preparation process of the composite material, because of a small number of poor bonding interfaces between the fibers and matrix, there are flaws and micro-cracks.

Compared with scattered abrasive with the same number grains, the removal rate is less.
The number of cracked dings in the workpiece surface decreases and the surface roughness become little to a certain value.
The number of cracked dings in the workpiece surface is little, the roughness rapidly decreases and become nearly unchanged at last.
When the grain size is big, high speed is chosen.
Grain type and grain size of polishing film.

As shown in Fig. 3, the as-forged Ti-47Al-2Cr-2Nb-Y alloy has refined streamline microstructure along radius direction composed of a large number of recrystallized grains and a small amount of retained casting lamella colonies.
At high temperature, disordered β phase could provide a sufficient number of slide systems and carries most of the deformation [7, 15].
This overcomes limited number of slip systems of the room temperature deformation in TiAl based alloys.
Strain compatibility among different grains is also improved.
Disordered β phase with bbc lattice provides a sufficient number of independent slip systems, which improves tensile properties.

Fine grain does not appear while the columnar crystal directly grow from the combination layer.This is different from the fine grain zone of the surface, columnar grain zone, equiaxed grain zone which are all formed during being casted.
This is when the laser clads, hexagonal structure α(Mg) solid solution of zone A and Mg matrix are fully coherent, while during the cooling process the grain grow directly as unmelt solid grains of the substrate surface as the nucleation center ,but limited number of the matrix grains result in a coarse columnar grains.
Massive dark figure is Mg2Si phase (a smaller number) by electron spectroscopy (EDS) analysis, we believe it reach zone B by convection and gravity.
Microstructure characteristics shows that a large number of dendrites located in the zone C.According to Electron Spectroscopy (EDS) analysis of figure 5, the coarse dendrites are Mg2Si phase and matrix is mainly β (Mg17Al12) facies.The molten Mg is reacted to Si of Al-Si eutectic alloy in zone C, then a large number of Mg2Si coarse dendrites is formed.
During the cooling process the melted Si separate out in the grain boundaries make the grain boundary coarsening.

China ajxu.cumt@gmail.com, bfanyu2002@hotmail.com Keywords: Fracture Toughness; Coarse-grained Heat Affected Zone (CGHAZ); X80 Pipeline Steel; Weld Thermal Simulation; Finite Element Analysis (FEA).
A large number of fracture toughness (as denoted by CTOD) tests together with 3D finite element analysis are performed using single edge notched bending (SENB) and tension (SENT) specimens at different temperatures.
Coarse-grained heat-affected zone (CGHAZ) is considered as the material microstructure in preparation of the weld thermal simulated fracture mechanics specimens.
Weld thermal simulation has been used to produce the microstructural properties of coarse-grained HAZ (CGHAZ) in X80.
A large number of CTOD (crack tip opening displacement) tests are carried out at -90℃, -60℃ and -30℃. 3D FEA are employed to model the crack tip stress fields of the tested specimens.

The steel sheet having the texture of the second group shows high r-value and good formability, therefore a number of studies have been focused on the texture formation and its utilization [4,5].
Journal Title and Volume Number (to be inserted by the publisher) 3 Figure 3 Recrystallisation occurred at grain boundary of {100}<011> by-crystal after 70% cold rolling and its texture.
A {h,1,1}<1/h,1,2> recrystallisation grain was found.
The pole figure shows the orientations at the interior of the grains and at the close point to the grain boundary.
Within A grain, the orientation slightly shifts at the close position to the grain boundary and its rotational direction was opposite to the orientation of B grain.

During high-temperature deformation, cavities are produced by stress concentrations at grain boundary triple points and striation bands due to grain boundary sliding.
By using microstructure materials roll formed under a light reduction rate after hot free forging with a small number of passes, the strength of this magnesium alloy at room temperature was ascertained after superplastic deformation was carried out at high temperature.
To examine the effect of grain boundary sliding and intergranular deformation on macroscopic deformation, grain boundary sliding was measured from the shifts angle of scratching lines on the specimen surface.
Deformation under biaxial tensile stress is applied in two directions subject to the grain boundary sliding resistance caused by grain boundary segregation.
This significantly affects grain boundary sliding with a slower strain rate, probably because there are a large number of cavities in the grain boundary triple points.

According to the initial grain size of 25 µm these measurements show, therefore, that ABE is effective in reducing the grain size of this Mg-based alloy.
The recorded grain sizes, however, were achieved by ECAP process after eight passes, where un-processed material possessed a grain size of 15~22 µm [9].
As the increase of strain, the size of fine grain is less affected by ABE passes, while the coarse grains are refined continuously by dynamic recrystallization [3].
Fig. 3 a) True stress versus true strain at room temperature for as-received and processed experimental alloy, b) Variation of the yield stress, UTS and tensile elongation with the number of ABE passes.
The more the number of passes the more pronounced hardening effect may be seen in the material.

It was found that FSW produced an equiaxed fine-grained microstructure in weld zone and the grain size in weld zone decreased up to about 4~6 µm with decreasing rotating speed.
In thermo-mechanical affected zone, the change in grain size was not significant, however, large number of low angle grain boundaries were observed, which seems to be concerned with the formation of subgrains due to the development of dislocation cells.
It is shown that the FSW process produces the reduction of grain size at WZ, whereas the change in grain diameter at TMAZ is not remarkable.
The grain size distributions in WZ are given in Fig. 6.
Fine-grained microstructure was developed in WZ by FSW.

For example, the grinding wheel wear is attributed to bond fracture, grain fracture, and attritional grain wear [1].
The result of grain shape measured using the SLM is shown in Fig. 2(b).
The obtained result yields a shape with clearer features of the measured grain.
The extraction method fails to approach the grain boundary in the cases that many pixels have the median value, there is a gap at the boundary between the grain and the bond, or the grain tip is far from the grain centerline.
The shape processing approach is applied for a number of grains and the obtained results are employed for measuring three angles on each prospective cutting edge of the measured grain.