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However, there are still challenges to completely develop the ability of CBN abrasive grains grinding in industry [4].
Porous vitrified CBN wheels have also some disadvantages, such as low grain bonding strength, tiny chip storage space and poor shape retention ability [6, 7].
The working layer of the wheel, which consists of 32 composite blocks, is manufactured using the mixture of Cu-Sn-Ti alloy powder (bonding), graphite particles (lubricant), CBN grains (abrasive), alumina bubbles (pore).
Comparison of these two figures, the number of effective dynamic abrasives in Fig. 9(a) is less than that in Fig. 9(b).

According to actual needs, people have developed a large number of magnesium alloy systems.
Magnesium alloy is sensitivity to strain rate, when strain rate increases, plastic deformation decreased significantly, some of the more complex magnesium alloy molding needs to forging several times, in order to avoid grain growth , successive reduces forging temperature.
Rapid solidification technology [5] Rapid solidification technology is a molding process emerging in recent years, the use of this technology can get very small grains, thereby enhancing the mechanical properties of alloy and thermal stability.
Matsuda etc. [6] using the technique exam Mg-Li-Si-Ag alloy forming , have shown that the alloy grain is very small, homogeneous, during which dispersed phase of MgSi.

Porous HAp can be produced by a number of methods: preparation from natural bone, ceramic mass foaming technique, polymeric sponge method, gel casting of foams, starch consolidation, microwave processing, slip casting, and electrophoretic deposition technique [5].
From data shown in literature, porosity and pore formation can be affected by the grain size of ceramic powder [19].
Table 2 Specific surface area and porosity of HAp bioceramics Sample designation SSA (m2/g) Open porosity (%) Closed porosity (%) Total porosity (%) HApSn 113.9 61 13 74 HApHEg 84.9 40 19 58 HApOEg 82.9 21 14 34 HApF 150.1 56 8 64 HApR 94.9 45 12 56 FE-SEM micrographs of porous HAp bioceramics obtained from CaO of different origins demonstrate differences in microstructure, including grain size and densification stage of bioceramics (Fig. 4).
Most explicit grain size and microporosity differences were observed between HApSn and HApR bioceramics.

The steel, which is widely used in mineral equipment, offshore drilling platforms, heavy machinery and ships, achieves its excellent properties of strength and toughness by having low carbon levels(less than about 0.06 pct) in combination with ε-Cu precipitation hardening, dislocation strengthening and fine grain strengthening, etc[1,2].
This effect is attributed to the refinement of effective grain size and the increased amount of stable austenite (reversed austenite) at lower temperature.
Firstly, a small number of island structure along the lath ferrite (i.e. high temperature tempered lath bainite) when quenching at 700°C.
When the temperature exceeds to 820°C(Ac3 transition point), the microstructure reverts to lath bainite, in which lath bainite coarsens and dislocation density reduces and a small amount of M/A island distributes along the grain boundaries, compared with the former microstructure of steel after first quenching.

Kamouneh [2,3] investigated the work-hardening effect of flat rolling on the critical regions of gear through the use of the hardness maps, grain-flow photographs and finite elements models.
The rolling parameters were the same for all materials: the pressure of the hydraulic motor (which provides the radial pressing) equal to 36 [bar], the revolution speed of the piece (which provides the rolling speed) equal to 1600 [rev/min] and the number of revolutions of the piece during the calibration period equal to 2 [rev].
The load was taken equal to 300 g, in order to take account of estimated micro-hardness and of grain size.
Vriesen, Investigation of work hardening of flat-rolled helical-involute gears through grain-flow analysis, FE-modeling, and strain signature, International Journal of Machine Tools & Manufacture. 47 (2007) 1285-1291

Experimental procedure Cu powder (grain diameter 47 μm, degree of purity 99%), Cr powder (grain diameter 40 μm, degree of purity 99%) and Zr powder (grain diameter 40 μm, degree of purity 99%) were mixed with AlN nanopowder (~50 nm) in a mass ratio (wt%) of Cu-0.5Cr-0.5Zr-0.1AlN, Cu-1.5Cr-0.5Zr-0.1AlN,Cu-3Cr-0.5Zr-0.1AlN,Cu-5Cr-0.5Zr-0.1AlN, and Cu-7Cr-0.5Zr-0.1AlN.
Brinell hardness was highest after the aging treatment at 700 °C, which indicates that the number of elements that precipitated, or the inter-metallic compounds, was higher than those generated at other temperatures.

There have been a limited number of studies evaluating the corrosion behaviour of semi-solid metal (SSM) formed Al-Si-Mg (3xx) casting alloys in the as cast and heat treated conditions [3-5].
The presence of the eutectic Si and Si particles induces corrosion attack between the matrix interfaces of primary α-Al grains with eutectic Si and the anodised layer with Si particle region interface.
The results obtained in this study lead to the following conclusions: Eutectic Si and Si particles are present in both the anodised layer and in the grain boundaries of the primary α-Al grains, · The fully anodised samples showed evidence of surface corrosion though the corrosion was not significant.

This technique has attracted the attention of a large number of researchers during the past 30–35 years.
The main characteristics of mechanical alloying can be the production of a fine dispersion of second phase particles, Refinement of grain sizes down to the nanometer scale, development of novel crystalline and quasicrystalline structures, Synthesis of amorphous phases and Promotion of chemical reactions at low temperatures [8].
Peak broadening is due to grain refinement, as seen from table 1; the crystallite size in the case of Fe72Al26Sn2 reduces to 6nm.
It is worth noting that the smallest grain size was observed in the case of tin addition [19] (see table 1), reduction in crystallite size is often accompanied by an increase in the lattice strain level throughout the MA process.

This is because grinding process commonly yields workpieces with good surface finish and high form/dimension accuracy even for difficult-to-machine materials in which the work materials are removed with extremely small and hard-brittle abrasive grains.
Abrasive grains serve as insulator to maintain the chemical individual reactions (anodic oxide) occurring in the machining gap between the tool and the workpiece to form an oxygen layer on the work-surface.
Then the oxygen layer is removed by abrasive grains for the sake of mechanical actions.
In ECG process, the electrolyte flow plays a crucial role; at high electrolyte flow rates, a large number of charged ions are available for electrochemical reaction [12].

The main conclusion from these research works is that grain (crystal) orientations are the major driving force of curved pins if the grain size is large comparable to the specimen size.
The non-annealed billets had a microstructure having approximately 46 µm grain size and hardness value of 50 HV.
Acknowledgement The authors would like to acknowledge the supports of Thailand Research Fund under the grant number MRG5980148, National Metal and Materials Technology Center (MTEC), Thailand, University of Toyama, Japan, Department of Mechanical Engineering, Northwestern University, USA, and Department of Mechanical Engineering, Faculty of Engineering, Khon Kaen University, Thailand.