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Rock strength and the ultrasonic velocity are related and a considerable number of empirical researches has been carried out to establish the correlation between the strength and velocity of sonic pulses.
Specimen numbers for the tests ranged from 13-25.
The very coarse-grained variety of the Jakura marble showed interpenetrating grain texture called decussate structure (Figure 2a).
The determining factor as to which mode obtains is dependent on the strength of the grain boundary relative to that of the grain interior.
Microcracking and grain size effects in Yuen.

Strip-shaped phase is observed at the austenitic grain boundary.
The severer plastic deformation in ferrite at the austenitic grain boundary can causes small voids form at austenitic grain boundary.
Fracture consists of large numbers of dimples.
Large numbers of deformation twins are observed, showing that the tensile specimen was deformed by twinning mode besides dislocation slip mode.
The second phase precipitation is observed along grain boundary.

Meanwhile, materials with ultra-fine grains manufactured through severe plastic deformation have different physical properties from general materials that have coarse grains[6].
During ECAP, the effects of strain hardening become effective until the critical pass number is reached.
However, the hardness tends to remain fixed after the critical number of passes[7].
TEM micrographs after different numbers of passes of ECAP.
However, after 8 passes of ECAP, ultra-fine grains were formed.

In this area, the grains are elongated towards the surface.
The size of coherent-scattering region X-rays of the grains of the c-ZrO2 phase is 15–20 nm.
The total number of pulses was N = 100 and 300.
It is seen that the shape of the grains in the melted subsurface region and that of the grains in the sample volume are radically different.
In the surface layers, the grains are oriented towards the surface to be treated.

Because the number of components fabricated by the high temperature carburizing to shorten the heat treatment time has gradually been increasing, the utilizing range of such steel is rapidly reducing.
All austenite grains are stable, as reported by Krauss [5].
In spite of omitting isothermal heat treatment, no abnormal austenite grain was found.
Note austenite grains in the samples of test 1; a), arrows in above graph indicate the censored and test 2; b).
grain was found in Fig. b).

The microscopy investigations revealed a difference in twin number and size after tension and compression, respectively.
The specimens had a random texture and an average grain size of 110 mm.
The deformation twinning in magnesium causes intensity variation between the (00.2)-(1.00) and (10.3)-(11.0) diffraction peak pairs, which correspond to the parent (grains undergoing twinning) and twin (twinned grains) grain families, respectively [8].
E.g. in tension those grains undergo twinning, whose c-axis is parallel to the loading direction.
In Fig. 3a the prediction of the total number of twins as a function of strain and loading mode is shown.

Moreover, the eutectic structure with rare earth distributes in the grain boundary clearly and the grain boundary is thicker.
There are a great number of primary  -Al phase that are fine, roundness and well-distributed.
The roundness of grain becomes worse and the amount of grain reduces.
Grains merge into bigger grains speedy and have directional properties.
The grains grow into dendritic.

It is interesting to notice that the grains with different orientations show different growth rates.
Grains with random orientations have much larger growth rates than any other texture components.
At the early stage (Fig. 2a), there are more nuclei or new grains (larger sizes) with random orientations (grey grains on the EBSD maps).
These randomly oriented grains grow faster, leading to an increased volume fraction of grains with random orientations.
Acknowledgements The authors would like to acknowledge the financial support from National Science Foundation of China (NSFC) under the contract number of 51171214 and 51001016.

A large number of single pulse deposits deposited and superimposed continuously and then deposition layers with a certain thickness were formed.
The epitaxial growth coating with columnar grains was then achieved by the micro-arc spark deposition.
Results and discussion The ASD coating is composed of a large number of single pulse deposits which were superimposing continuously.
Columnar grains with almost the same orientation were obtained at a higher temperature gradient.
The columnar grain dendrite passed through sublayers and grew continuously.

The idea of SMAT is to introduce a large number of defects and/or interface into the surface layer by plastic deformation, which is realized by the repeatedly impacting of flying balls to the material surface.
The accumulation of plastic strain and the increasing of strain rate along the depth from the deep matrix to the top surface of the treated material will gradually refine the original coarse grains into ultra-fine grains (ufg) and/or nanometer-sized grains.
The grain size of the top surface can be refined into nanometer range, with an average grain size of a few nanometer to tens of nanometer (Table 1), which may vary with materials [6-13].
Generally, dislocation activity and twining will intertwine each other during the deformation process and will generate various configurations of dislocation arrangement (e.g. dislocation walls, tangles, arrays, etc.) or twins to subdivide the original coarse grains into sub-grains or cells which will finally be divided into nanometer-scaled grains.
Variation of the COF with the number of cycle for the SMAT Cu and the CG Cu samples against a WC-Co ball in mineral oil under the given test parameters: normal load of 50 N, frequency of 20 Hz, slip amplitude of 50 µm and fretting cycle of 72000.