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Quartz sand with a grain size of 0.2 - 0.8 mm was chosen as an abrasive material.
Matrix properties and structure Sample number Solid solution composition Microhardness of solid solution, N/ mm2 Type of eutectic carbides Microhardness of eutectic, N/mm2 1 Austenite + martensite 7900±750 Cr23C6 8600±650 2 Austenite 3000±450 Cr7C3 Not def. 3 Austenite + ferrite 4300±550 Cr7C3 Not def. 4 Austenite Austenite + martensite 3900±450 4900±550 Cr7C3 Not def. 5 Austenite Austenite + martensite 3000±350 4700±750 Fe3C 7500±850 6 Austenite 5200±550 Cr7C3 7800±750 7 Austenite Perlite 6500±750 3900±450 Cr23C6 Not def. 8 Austenite + martensite 6100±450 Cr23C6 8900±750 9 Austenite + martensite 6200±450 Cr23C6 8900±950 10 Austenite + Perlite 5100±450 Fe3C 5900±550 11 Troostite + perlite 4900±550 Fe3C Not def.
Alloyed Tungsten Carbide properties Sample number Amount of carbides, % by volume Average length of intersection line of WC phase, μm Lattice parameter, nm Amount of solid solution, % by volume Amount of eutectic, % by volume 1 7 2.2 0.42705 66 24 2 13 3.6 0.42640 41 43 3 14 4.56 0.42511 81 1 4 13 2.54 0.42520 71 13 5 11 7.85 0.42575 49 37 6 13 3.29 0.42969 48 36 7 13 4.48 0.42511 33 51 8 20 7.1 0.4215 48 29 9 14 5.6 0.42604 60 23 10 3 1.9 - - 95 11 10 5.47 0.42556 60 27 Thus, after solidification, the deposited metal has the following structure.
It is noted in [1] that if the deposited metal contains troostite or sorbitic grains of a solid solution with a carbide mesh, then the wear resistance drops sharply, which is also confirmed by our research results.
Microstructure of deposited coatings Sample No. 3 (Fig. 2, a) differs from the rest of the group in the structure of the deposited metal, here crystallization of the matrix began with formation of δ-ferrite grains and ended with formation of a small amount of eutectic based on Cr7C3 [4] compound.

Due to the short sintering duration (usually up to 1-2 minutes), the High-Pressure High-Temperature (HPHT) method is suitable to prevent a recrystallization process and simultaneously limit grain growth [14].
The purpose of the presented work is to study the influence of initial Si3N4 and SiC powders grain size (nano, micro and submikro), quantitative composition of mixture (Si3N4:SiC ratio) and sintering parameters on mechanical properties of Si3N4-SiC composites obtained by the HPHT method.
The insufficient mechanical properties of micro-sized Si3N4–SiC materials can be attributed not only to grain size but also to specific properties of the initial powder resulting from their production method (e.g. shape of the grains, impurities, oxidation etc.).
For all investigated samples, independent of their grain size, a strong influence of indentation load on hardness values can be observed.
Project fund by The Polish Ministry of Science and Higher Education (Project number: DPN/N111/BIALORUS/2009).

(i) (f) (g) (h) (e) (d) (a) (b) (c) Fig.1 Microstructure of laser transformation hardening layers(a)morphology (b) left side of crescent(c)right side of crescent (d) incident angle is 10°(e) incident angle is 25°(f) incident angle is 15°(g) incident angle is 20° (h) incident angle is 20°(i) incident angle is 30° The heating and cooling rate in laser transformation hardening can reach 103 ℃/s, which generated great phase transformation driving force, so the number of austenite nucleation sharp increased.
At the same time, rapid heating of the moment austenitizing, let austenite grain no time to grow up, resulting in significant refinement of austenite grain size, which change into small martensite.
Different laser incident angle caused different microstructure of the surface, the reason was that, with the laser incident angle decreases, the spot of the average power density increases, 40Cr steel surface absorb the laser energy increases, the large laser energy density made the temperature of metal surface increased further, speeding the steel heated to austenitizing temperature, austenite transformation fully, and thus more martensite obtained, and because a larger surface cooling rate, large undercooling, martensite grain no time to grow up, in the subsequent cooling process martensite obtained will gradually become small.
As can be seen from the  curves, the hardness significantly increased after laser transformation hardening treatment, this is mainly because of martensite was refined, the grain nucleation rate greatly increased, resulting in very small uniform hardened layer, which showed a fine hidden needle shape.
Grain nucleation rate greatly increased, resulting in very small uniform mcrostructure in hardened layer, showed a tiny hidden needle shape, thus improving the corrosion resistance.

Grain deformation shows that impact direction was from left to right.
The grain size is not increased with respect to the initial grain size of the material, i.e. there is no grain growth caused by heat, like in fusion welding processes.
Hence, no micro-structural changes caused by heat are found (no heat affected zone, no grain growth, no strength losses).
Bruckner: BHM Berg- und Hüttenmännische Monatshefte Volume 153, Number 5 (2008) ,pp. 189-192 [3] G.

Introduction Equal channel angular pressing (ECAP) has been successfully applied to produce ultrafine-grained materials through severe plastic deformation (SPD).
Owing to no substantial change in outer dimensions it is easy to repeat the pressing form many times and get a large accumulated strain, which can be estimated by the equation [6]: (Eq. 1) where b and ψ are the corner angle and the die angle, respectively, and N is the number of passes [5].
The process can be varied changing the rotation angle of the billet about its longitudinal axis (x) between consecutive passes and are designated as A (x = 0o) , B (x = 90o), and C (x = 180o) The deformation textures orient the slip plane between the shear direction, which is b/2, and the grain elongation direction.
The grain refinement during the ECAP process is affected by accumulative strain and the interaction of shearing plane with crystal structure and deformation texture.
After annealing at 350 oC for 1 hour all samples achieved a relatively homogeneous fine grained microstructure with grain diameters around 20 to 30 mm.

A large number of studies showed that there are a variety of wear mechanism existing, generally, believed that the wear resistance of ceramic materials are related to their hardness, toughness, microstructure, defect type and material hardness and abrasive hardness.
The inelastic deformation region is mainly plastic deformation, micro cracks, grain refinement and fragmentation in microscopic material powder, the high hardness and brittleness of ceramics make them easily to produce Surface / subsurface damage in the grinding process, the damage including microcracking, microscopic plastic deformation, phase transformation, residual material, grain refinement and fragmentation powder, the macroscopic crack ( median/radial crack and transverse cracks), pores and loose area collapse pit.
The removal of material , on the one hand is due to the front material of the abrasive particles cutting edge is squeezed while the abrasive particles cutting into the workpiece, when the compressive stress exceeds the limit stress of the ceramic material, it is crushed to form a large amount of debris, on the other hand, due to the pressure stress and friction heat, materials below abrasive grains produce local plastic flow and to form deformation layer, after the abrasive grains across, the stress disappears, which causes the deformable layer is detached from the workpiece and form chips, deformation behavior and crack system of ceramic material under abrasive effection can be illustrated in Figure 1 When the material is precision grinding.
When the cutting depth of the abrasive grains further increase the material of non-elastic deformation region under load will increase the lateral flow, non-elastic region is further expanded. the material of the elastic region will be generate friction stress in the non-elastic region / elastic zone boundary due to the friction effect, friction stress makes the elastic zone boundary materials produce tensile stress, when the tensile stress exceeds the ultimate stress of the material (tensile strength), median / radial cracks will form. it is in the place of the maximum tensile stress or in non-elastic / elastic boundary existing one or a plurality of micro-cracks that produc new microscopic cracks.

The material was > 99% dense and consisted of nearly 100 % tetragonal zirconia, with the mean grain size of 0.51 µm.
For the specimens that failed before 10 6 cycles, the number of cycles to failure was registered.
In both cases the tetragonal grains on the surface were found to be partitioned and distorted, indicating that the reverse m-t transformation has occurred.
The intrinsic strength of the dry specimens of about 1000 MPa corresponds well to commonly reported values for pressureless-sintered 3Y-TZP ceramics exhibiting a comparable grain size.
It was found that the partitioned tetragonal zirconia grains and pre-existing monoclinic zirconia in the ground and sandblasted surfaces hindered the propagation of the diffusion-controlled transformation during subsequent ageing, but they do not have a potential for preventing water-assisted stress corrosion process under prolonged cyclic loading in an aqueous environment.

In the derivation, the atomic transportation by electromigration is assumed to be given as follows: ( )       ∂ ∂Ω −       Ω−−Ω+ − = ∗ l N N jeZ kT NNNQ kT ND T T gb 0 * 0 0 exp κ ρ σ κ J (1) where J is the atomic flux vector, N atomic density, D0 a prefactor, k Boltzmann's constant, T the absolute temperature, Qgb the activation energy for grain boundary diffusion, κ the constant relating the change in stress with the atomic density under restriction by passivation[6], NT the atomic density under tensile thermal stress σT, N0 the atomic density at a reference condition, Ω the atomic volume, Z* the effective valence, e the electronic charge, ρ the temperature-dependent resistivity.
By considering Eq.(1) and the atomic flux divergence in the grain boundary, in the polycrystalline Al line, the governing parameter for electromigration damage is given[2] as Eq.(2).
where the constant C*gb is the product D0δ /k denoting the effective width of the grain boundary by δ, d the average grain size, and ∆ϕ a constant related to the relative angle between grain boundaries[2].
The parameter AFD* gbθ gives the number of atoms decreasing per unit time and unit volume and is associated with void and hillock formation.

Since aluminum components may undertake various impact loads in practical usage, a number of studies have been contributed to relationship of microstructure with impact properties.
Fig. 2 indicates that coarse grains with large SDAS occurs in the region A.
Compared to the region A, finer grains can be found in the thin-walled region C.
In the A356 alloy with large SDAS, the eutectic Si particles are often coarse and clustered along both cell and grain boundaries.
The crack has a length over 1mm and extends through the rupturing of eutectic matrix on the grain boundaries with a little deflection.

Grain refinement is the only mechanism to increase both strength and toughness at the same time.
Thermo-mechanical-controlled process is applied to maximize grain refinement.
The deformed austenite provides more nuclei for the γ/α transformation, α-phase nucleates predominantly at deformed austenite grain boundaries and deformation bands.
Reducing carbon contend can make more niobium content dissolving in austenite at high temperature, therefore the function of niobium to refine grain act effectively [5] .
There are a large number of very fine precipitated particles which size is about nanometer level in the acicular ferrite steel and interact with dislocation, as in Fig.3.