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The actual crystal lattice differs from the ideal lattice in that it has a large number of point failures, dislocations and etc.
The progressing dislocations cause new dislocations, their number in the crystal lattice is growing rapidly, plastic deformations can continue.
The microstructure of the analyzed sample consists of perlite (dark grains).
Perlite arose out of originally austenitic grains as a product of eutectoid conversion.
Perlite grains are flanked by proeutectoid ferrite (light fields).

It was found that mullite presence leads to reduction of the grain growth rate and thus decreases the microcrack density in the materials.
Microcracking phenomenon in tialite ceramics is widely recognized to occur when the microstructure consists of grains which are larger than a critical grain size, laying the range of 1-2µm [3, 6].
Al2TiO5 particles might be nucleated on the Al2O3 grains and the small size of Al2TiO5 particles grow and contact with each other.
Grain growth is obvious in Fig. 4 (e,f) generally, and among these two samples, SEM image of AT4 shows more grain growth and 9ATSB4 microstructure is finer in comparison of non doped sample (AT4).
Nagoya; United states patent, number: 4,767,731 NGK Insulator, Ltd., Japan, (1988)

The corrosion was attributed to dissolution of the metallic ions at the grain boundaries related with sintering additives.
The excellent corrosion resistance was plausibly due to the strong grain boundaries of the materials.
The SEM observation revealed that the PSN generally has a microstructure of fibrous grains (see Fig. 2) while the PSA tends to consist of equiaxed grains.
Such a small deterioration of the properties suggests that the sialon specimens have strong grain boundaries.
It was suggested that the excellent corrosion resistance was due to the strong grain boundaries of the materials.

The microstructure also shows segregation free grains with clearly visible grain boundaries.
Also because of the high strain rate of hot rolling, few dynamically recrystallized grains/sub grains are seen which is in good accordance with the work of Jiang Na et [3].
The sub grain size is of the order of 10 micron.
In transverse direction also, elongated grains with fibrous structure and no obvious grain boundaries are noticed.
Large number of scattered secondary cracks and possibly at grain boundaries (all of which are more or less parallel) are found to be present and these appear unusually deep.

However, its plastic deformation and formability are poor, especially when the grain of as-cast magnesium is bulky.
The size of centrosymmetric compounds is about 50mm and shape is number of the petal is five.
Fig. 3（Ⅰ）shows that the grain size of matrix microstructure is very bulky and the boundary of grain is clear, the as-cast microstructure is made up of the bulky α-Mg matrix, the coarse and continuous divorced eutectic β-Mg17Al12 phase which unevenly distribute in the grain surrounding and a little layer-like (α+β) eutectic structure.
More new born compounds diffusely distribute in the α-Mg matrix and near the grain boundary.
On the other hand, the Mg3Zn6Y quasicrystal particles as strong pinning centers for grain boundaries could prevent grain boundary slip due to its high thermal stability [14].

There are a large number of binary and ternary phases in the ternary system, both stable and metastable.
The structure of Fe-28Al-15Si-0.2Zr alloy is coarse grained with grain’s dimensions in order of hundreds micrometers (see Fig. 2).
Secondary phase particles are observed mainly on grain boundaries and only rarely inside the grains (see Fig. 2 and Fig. 3).
Small areas of eutectic form on grain boundaries rarely (see Fig. 5).
No grain coarsening is observed after annealing at high temperature of 1000 °C.

In the same technological conditions, the interfacial structure of the PDC layer and WC-Co substrate has little influence on the abrasion performance, and the diamond and grains can sinter better, causing the excellent abrasion performance of PDC.
Table 1 samples serial number and their picture Number 1# 2# 3# 4# 5# Interface planar structure v-groove u-groove Ring groove Ring claw-tooth picture The experiment parameters.
In the same technological conditions, the interfacial structure of the PDC layer and WC-Co substrate has little influence on the abrasion performance, and the diamond and grains can sinter better, causing the excellent abrasion performance of PDC.
Beside, most of crystalline grains in the diamond layer have combined into the D-D structure.
In the same technological conditions, the interfacial structure of the PDC layer and WC-Co substrate has little influence on the abrasion performance, and the diamond and grains can sinter better, causing the excellent abrasion performance of PDC.

The typical microstructure is characterized by a coarse fraction, in order to increase porosity (and hence thermal insulation) and improve thermal shock resistance (by grain bridging mechanism).
Moreover, the presence of large grains in a fine- and medium- grain matrix allows grain bridging mechanism that improves thermal shock resistance.
Experimental procedure A mixture of commercial alumina (ALMATIS, Tabular T60 and CT 3000 SG) and ceramic wastes (two grain size fractions), previously optimized and characterized [6], was used to manufacture alumina-mullite prototypal tiles.
Mixture composition (%w/w) Al2O3 grain size 1mm ÷ 3.35 mm 27.1 45 μm ÷ 300 μm 19.2 45 μm ÷ 63 μm 19.2 Ø50 = 0,8 μm 14.5 Ceramic waste grain size Ø > 700 μm 10 250 μm < Ø < 700 μm 10 Tab 1: Composition of the mixture containing ceramic waste used to manufacture prototypal tiles.
The thermal shock resistance is evaluated by inspecting the visible crack length and determining the number of cycles to fracture.

The paper also presents microhardness and grain size measurements carried out together with microstructural observations in the SEM.
dN [mm/cycle; MPa.m0.5] ; N-number of cycles [cycles] (1) cm c I da =C ×K .
Results of optical microscopy for the microstructure of the material near the fatigue crack (Fig.5 a,b,c) and analysis of the fracture surfaces carried out with the SEM (Fig.5 d,e) shown that the failure mechanism at test temperatures (Table 1a) is almost transgranular - the crack propagates mainly across the grains - althougth with slighly intergranular contributions (Fig. 5 d,e).
The ASTM grain size was measured before and after any experimental test using the Abrams Method [9], being always approximately equal to 7.
' y k P E σ α ⋅ = ⋅ ⋅ (5) Conclusions Until 500ºC, the material showed: a) high metallurgical stability, not changing its grain size, nor precipitating chromium carbides; b) relatively high mechanical properties, together with high ductility; d) mainly transgranular fatigue crack propagation; e) high creep crack growth resistance.

The major types of inclusions in practical disk were Al2O3 and Al2O3-SiO2, the inclusions run through several grains, no matter Al2O3 or Al2O3-SiO2.
By comparing number and size of defects in material, the quality of corresponding production process is revealed.
The distribution of inclusions in grain size and the peripheral γ′ phase of inclusions were showed in Fig.6 and Fig.7.
It was clear that the inclusions run through several grains, didn’t merely exist in grain and grain boundary, no matter Al2O3 or Al2O3-SiO2, especially the Al2O3-SiO2 inclusion distributed several grains reticularly and intermittently.
The inclusions run through several grains, no matter Al2O3 or Al2O3-SiO2.