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Although series of crack control measures were adopted, the internal stress of the coating will still become more and more big and the trend of crack formation increase with the increase of clad layer number.
As shown in Fig. 3 b, the fully melted region of the laser-clad ceramic coating consists of fine equiaxed crystal grains.
As it can be seen, the grain size of the bottom fully melted region is bigger than the top one.
Therefore, the average grain size of the bottom area is larger than the top position.
According the Hall-Petch empirical relationship, the hardness increases with the reduction of grain size.

According to the published reports [6,7], these particles are primary Al3Sc particles, which can be taken as heterogeneous crystal nucleus used to fine the grains.
The theory of cold hardening explains that cold drawing can produce distortion of the lattice, grain boundary breaking, accumulated energy and decreased active energy for subsequent recovery or recrystallization of grains during artificial aging and natural aging.
The mentioned energy will speed up the recovery or recrystallization of grains and partially eliminate the cold hardening produced by CDAA process (see Fig.1 (f)).
As is show in Fig.1 (g), there are a large number of fine second-phase particles in the Al-matrix.
A great number of dislocations and fine Al3Sc particles are dispersed in Al-matrix.

The three ceramics had similar grain size and varied in binder content.
In light of this a statistical analysis incorporating Weibull, normal and lognormal distribution functions has been carried out on the strength data of a number of advanced ceramics.
The three grades had a constant grain size with varying binder content.
When microstructures contain grains and pores it is often difficult to distinguish where initiation takes place, from a grain boundary or from a pool.
It is likely that over a number of tests failure will initiate from both these flaw types and that interaction between the grains and pores will cause deviation in the strength distribution throughout a particular test set.

It has been demonstrated convincingly in many occasions that ECAP offers an efficient and flexible way for structure refinement, formation of high-angle grain boundaries (HAGB) and creation of a variety of grain shapes.
However, the comparison was often performed with the coarse grain fully annealed counterparts.
Figure 5 shows that, as follows from the σFL-σUTS relation, the fatigue life is reasonably increasing with the number of ECA-pressings, i.e. with increasing monotonic strength (Fig.3) caused by dislocation accumulations and grain (cell) size reduction.
"CG" stands for "coarse grain" Cu with 115 µµµµm grain size.
Tome, in: Ultrafine Grained Materials II, edited by Y.T.Zhu, T.G.Langdon, R.S.

This led to coarse columnar grain structure.
The parts manufactured with WAAM technology are of excellent quality and, for example, the number of pores created in the structure during the WAAM process is relatively small [3].
This led to coarse columnar grain structure, as shown in band contrast image in Fig. 2a.
The maximum number of cycles was 2 million.
This led to coarse columnar grain microstructure. 2.

The ECAP technique at room temperature homogenized its heterogeneous dendritic microstructure and formed the ultra-fine grains of solid solution.
Their average size increased from 0.5 µm (as-cast state) to 3.0 µm and their number per unit area decreased, as indicated in Table 2.
The average size of eutectic Si-particles decreased to 2.5 µm and their number per unit area increased to 1.5x104 mm-2 in comparison with the heat treated alloy state due to the fragmentation of coarse particles.
During ECAP processing, the ultra-fine grained alloy structure was formed consisting of grains and/or subgrains of elongated shape with curved or wavy boundaries and high dislocation density (Fig. 5b).
The grains and/or subgrains with low angle (LAGB´s) and/or high angle grain boundaries (HAGB´s) were observed in alloy substructure.

Iron losses of grain-oriented electrical steels, is sensitive to the distortion of the supply voltage waveform of the excitation winding.
In the present paper, an experimental apparatus is developed in order to evaluate the effect of distorted supply voltage waveform on iron losses of grain-oriented electrical steels.
Experimental setup A 16 turn excitation coil was supplied from a programmable ac power supply (California Instruments MX30) in order to magnetize a number of magnetic cores with different voltage waveforms [4].
The magnetic cores are constructed of conventional grain-oriented or high magnetization grain-oriented electrical steel [5], [6].
The value of the parameters for the conventional grain oriented electrical steel M4 and the high magnetization grain-oriented electrical steel (lamination thickness 0.27 mm) were used.

The microstructure of fly ash particle reinforced aluminum matrix composite without suspending agent shows relatively coarse grain(see Figure 1a), when suspending agent added, grain refinement appeared (see Figure 1b).
When the suspending agent added into the liquid metal and mixed, which will be melting into the liquid metal quickly to form a dispersion of solid phase particles with a fine grain "Gene".
The effect of these solid-phase particles in the liquid metal are: First, it can be used as external nucleation substrate to form a large number of nucleation in crystallization; second, suspending agent in the liquid metal can form a large number of dispersoid, resulting in greater composition fluctuations and energy Fig.1.
fluctuations, contribute to the formation of fine grain structure; third, suspending agent is equivalent to a large number of internal cold iron, which will make the surrounding liquid metal form a large undercooling, change its equilibrium solidification crystallization mode, and solidification rate increases, so that the composition segregation of grains cannot formed and the organization have been significantly improved.
However, from the microstructure (see Figure 1b), significant grain refinement only appeared in the local, it is difficult to obtain the overall organization of grain refinement, which is related to the number and size of suspending agent, and parameters of suspension casting.

The resulting shows, many fibrous β-Si3N4 grains grown from the internal wall of the round pores, and the porous distribution uniform in the matrix.
Both the grains and suitable interfacial bonding strength contribute to the high fracture strength.
As can be seen, the samples mainly composed by β-Si3N4, a small amount of large-size grains surrounded by a large number of fine grains, which formatted a "dual mode" organization.
Pull out of β-Si3N4 grains content on mechanical properties Figure 5 shows the pull out of Si3N4 grains, as shown, long rod-like grains pull out from matrix and left empty, indicating the material has the proper interface combination strength, both β- Si3N4 grains and suitable interfacial bonding strength contribute to the high fracture strength.
The high mechanical properties at high porosity are attributed to the self-toughened elongated grains[6].

In the case of fine grained magnesium alloys, superplastic properties have been widely reported.
The reduction of m was attributed to significant grain growth of the alloy when deformed at 450°C.
Microstructural observations of the samples after deformation showed that grains elongated with strain, supporting the idea that GBS was very limited for this alloy, as expected for its initial grain size.
One can note that such a conclusion about the contribution of GBS and dislocation creep can be difficult to draw from the study of grain shape variation with deformation conditions since in the case of Mg alloys, both dynamic recrystallization and grain boundary diffusion can contribute to an apparent maintain of equiaxed grains with deformation.
A detailed comparison between the cavitation characteristics (i.e. cavity size, number of cavities per mm 3, coalescence extent…) in the two alloys is presently in progress.