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The average grain size of the material was found to be 30µm.
The Rockwell hardness number (HRC) is calculated based on measurement.
The average grain size is estimated to be around 30µm.
Average Grain Size Measurement Fig. 4.
The Rockwell hardness number (HRC) is calculated based on measurement.

The microstructure shows different grain size with different composition x.
In the last decades, a large number of researches have been carried out on lead-free piezoelectric ceramics to substitute for the widely used PZT for high performance applications [2].
Large number researches explained complex phenomena of MnO2 with perovskite structure, which the local atomic structure around Mn ions plays a crucial role in magnetic, electronic and transport properties.
The microstructure of the ceramics shows square- or rectangular-shaped grains and some large abnormal grains.
It is evident that the average grain size increases with increasing MnO2 content, indicating that MnO2 addition promotes grain growth.

As showed in Fig.3 (a), a large number of fine precipitates with the dimension of several nanometers dispersed in the matrix.
Firstly, the grain size of raw materials is the premise to ensure the size of grain and favorable texture of hot-rolled steel and cold rolled steel plate.
In this study, C and Mn steel are the main alloying elements, by adding these two elements, a large number of carbonitride precipitated in Iron.
Secondly, precipitates during annealing process restrict the grain boundary to move and restrain grain growth excessively, playing the role of grain refinement.
With an increase of the coiling holding time, the number of precipitates grows.

The measured resistivity is influenced by a number of microstructural factors such as the precipitate size and the volume fraction, the vacancy concentration, the concentration of solute in the matrix etc. [6].
Grain size analysis was conducted by the line intercept method.
Grain size corresponding to each heat-treatment case was obtained as an average from multiple specimens.
A LEO 1530 scanning electron microscope was used for examining sub-grain microstructural features.
The average grain size post-vacancy stabilization at 1045°C increased by not more than 15% of the as-solution-treated grain sizes.

This relationship can be explained by the influence of amorphous carbon content, vacancy density and grain size on the residual stress.
Since CVD diamond coating is mainly poly-crystalline, the grain orientation are different.
In the analysis of Raman spectra, the residual stress in the sample mainly shows compressive stress when the spectra peak moves to higher wave number, whereas for the tensile stress.
According to the results of Raman spectra, when the temperature was 650 ℃, although the more sp2 structure carbon content would lead more compressive stress, the thermal stress and more grain boundaries caused by smaller grain offset the compressive stress to some extent.
While the grain size did not change much compared with that under 750℃, the tensile stress in the coating could not offset the compressive stress effectively.

The result demonstrated that the slag forming material of TiO2 and Al2O3 tenders to form the framework structure of slag, while CaO and MnO2 inclines to incorporate in the grain boundary.
The white block grains distributed at some direction, and some gray tiny layer phase distributed at the boundaries of block grains.
Overall, the distributions of the Ti, Al and O elements cover most of the framework structure, while the Ca, Mn and O elements incorporated in the grain boundary.
The reflection peaks (2θ=34.9°, 37.3°) of slag sample 1# matched well with the standard of Mn2TiO4 (PDF number: 05-0689) given in JCPDS data file, which might be formed by the reaction between MnO2 and TiO2 during the welding process [7].
Those peaks of Mn2TiO4 were also found in the patterns of slag sample 2#, and the other peaks of sample 2#(2θ=43.2°, 62.7°) were consistent with the standard of Al3Ti5O2[8] ( PDF number: 50-0834) and Mn2AlO4 ( PDF number: 29-0881) respective.

There are studies[6,7] pointing out that M/A constituents with different morphology could strengthen the microstructure, but meanwhile they destroyed the continuity of base metal, and compared with blocky M/A, long-bar or angular M/A would dissever base metal and cause a certain number of lattice distortion, which deteriorated impact toughness.
By the statistics and analysis of grain size in simulated CGHAZ under different heat input, the results indicate that as heat input increases (from 6KJ/cm to 30KJ/cm), mean grain sizes in CGHAZ of 1# steel are respectively 39.8μm, 40.2μm, 40.1μm, 44.3μm, 44.8μm and 45.7μm, and mean size of original austenite grains has little increase; mean grain sizes in CGHAZ of 2# steel are respectively 30.6μm, 33.8μm, 44.7μm, 45.5μm, 56μm and 69.8μm, and mean size of original austenite grains has obvious increase, especially when heat input is higher than 20KJ/cm, it is found by the further combination with microstructure characteristics that mean grain size rises obviously after 30KJ/cm which is more than twice the size of 6KJ/cm.
What’s more, austenite grains are variable in size and there are small grains among big ones, which indicate the increase of heat input worsens both microstructure uniformity and toughness [8].
High alloy content inhibits the growth of austenite grains.
Microstructure of 1# steel is mainly composed of granular bainite, bainite ferrite and M/A, and the grains are fine.

Although the synthesis of high purity alumina powders has been successfully achieved in a large number of publications, the consolidations of powders to full or nearly full density without appreciable grain growth are still a practical challenge[7].
The samples with an average grain size around 500 nm were obtained, which had a relative small grain growth compared with the precursor powders adopted.
In the TSS method, the sintering proceeds at low temperatures, which may keep the grain-boundary diffusion active but suppress the grain-boundary migration, for the grain-boundary migration has a higher activation energy than the grain-boundary diffusion [42].
A full-dense structure with the grain size of ~500 nm was achieved, a remarkable decrease in grain size were achieved compared with that of samples produced by conventional sintering[45].
It was proved that under very low vacuum pressure, oxygen partial pressure could deplete the diffusion from the contracting grain to the expanded grain[47].

It can be seen from the picture that there is crystal phase precipitation in the glass ceramic sample S1, but the grain is smaller and the number is less.
In the sample S2, the grain number and size increases.
The grain number of sample S3 increases obviously, and occurs grain reunion phenomenon.
As can be seen from Figure 3, with the increase of holding time, the degree of crystallization increases gradually, and the grain size and number also increase.
The transmittance of sample S4 is the lowest, with the increase of holding time, the grain size and number is large, and the grain reunion phenomenon is obvious, so the scattering degree of the beam is the biggest.

For a given route and pass number, the texture developed with Φ = 120° is generally weaker than its counterpart with Φ = 90°.
Introduction Equal channel angular extrusion (ECAE) has been successfully applied to produce ultrafine-grained materials in various materials through severe plastic deformation (SPD) [1,2].
It is also not yet confirmed that the optimal processing route for grain refinement is always among the three basic routes.
It had equiaxed grains with an average grain size of about 60 μm (see Fig. 1).
The textures are the weakest with route R180 for both die angles, regardless of the pass number.