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The heat-treated material samples were mechanically polished and chemically etched by the Graff & Sargent etchant (84ml of H20, 15.5ml of HNO3, 0.5ml of HF and 3g CrO3) for 10-15 minutes to evidence the grains borders.
Figure 1 (a) shows the material microstructure in the as-delivered condition that presents an average grain size of 42 mm.
Figure 1 (b) shows instead the material microstructure after being heat-treated at 450°C for 120 s in furnace: it is worth to notice that no appreciable differences can be seen between the microstructure of the as-delivered condition and the microstructure of all the heat-treated samples both in the size and morphology of the grains.
The same figure shows the fracture surfaces for some representative testing conditions, which demonstrate the occurrence of ductile shear fracture and the enhancement of the material ductility at increasing testing temperature in terms of increasing number and dimensions of dimples.
Figure 5 shows the microstructural features of the sample zones close to the fracture area at different testing temperatures at strain rate equal to 0.01 and 0.1 s-1: no appreciable differences in the grain size and morphology can be seen, proving that the applied thermo-mechanical cycle does not change the initial material microstructure.

Fine grain sizes improve simultaneously deep drawability, yield stresses and total elongation, therefore it is important to obtain maximum grain refinement during the process of strip rolling and of transformation from austenite to ferrite.
The main grain controlling mechanism during strip rolling and in particular of IF steels is DRX followed by MDRX.
All numbers are given in % weight, except for C and N with numbers given in ppm. α Fe, with no microalloying elements, was used as reference alloy.
XDRX, the volume fraction of the recrystallizing grains was calculated by assuming this volume to be proportional to )/()( * ss ss e σσσσ −− , as shown in Fig. 3b.

The more the number of dislocations, more will be the restrictions to the movement of dislocations.
Table 1 Ultrasonic power vs tensile strength and hardness Ultrasonic Power (kW) Tensile Strength (MPa) Brinell hardness number 1.0 260 100 1.5 265 105 2.0 281 120 At 1 and 1.5 kW ultrasonic power, B4C nanoparticles were agglomerated which were observed in SEM images.
The major strengthening mechanisms associated with the particle reinforced composites are as follows; increased dislocations density-dislocations are increased due to the larger difference in thermal expansion coefficient and elastic modulus mismatch between Al and B4C, Hall-Petch strengthening due to grain refinement-Grains are refined due to the addition of nano-B4C and also due to ultrasonic cavitation effect.
Katgerman, Influence of ultrasonic melt treatment on the formation of primary intermetallics and related grain refinement in aluminum alloys, Journal of material science, 2011, 46, 5252–5259
Ma, Ultrasonic grain refinement of magnesium and its alloys, InTec, Available from: (2011)

V-EPC has been focused in the past years because it has a number of attractive characteristics[3,4].
Experimental procedures V-EPC process of diamond wheels consists of a number of stages as shown in Fig.1.
It can be known that the microstructure of the metal matrix consists of needle shaped Si and Al solution(α).The grain size was measured by metallographic image analysis system of OLYCIA M3.
It revealed that small grain size can be obtained in the whole cast, but the upper part of the sprue had larger grain size.
Conclusions By using V-EPC process, Al-Si based bonded diamond grinding wheel with small grain size in the whole cast can be obtained.

Because of the high equivalent strain associated with size invariant processes, more intensive grain refinement and higher hardness than rolling are achieved in many metals and alloys.
A large number of research work was done on strain induced α' and transformation induced plasticity (TRIP) [6-8].
The value of equivalent strain (εe) imposed on samples was estimated by means of the von Mises equation, (1) where R is distance from sample center, N is number of HPT turns and t is thickness of sample.
The edge region is totally featureless while the center region exhibited equiaxed grains with visible grain boundaries.
At 600o C softening is observed and this can be attributed to stress relief, recrystallization and grain growth.

Microstructural studies revealed the phase modification influences the grain growth and density of the PZT ceramic, but is required that the modifications do not add conductive intergrain defects.
Others changes are also related, such as the reduction of Curie temperature [7], predominance of tetragonal phase over rhombohedral one and grain growing during sintering [8].
After calcinations for 3 hours at 700ºC, the powder samples presents no secondary phases and two types of perovskite phases could br identified according the XRD diffraction data bank: rhombohedral (R3mR - ICSD card number #77585) and tetragonal (P4mm - ICSD card number #90699).
The higher weight loss for non modified PZT and consequent ceramic porosity seems to be correlated to the PbO deficiency in triple point of the green grains during the densification stage.
Loss tangent for all of the samples is low, what reveal that no conductive defects were generated in grain boundary.

Because of the unique properties of the amorphous structure, such as homogeneous composition and lack of defects, grain boundaries, second phase, several researchers had used amorphous ribbons to produce nanopore materials or nanopore / metal oxide materials using an alkaline solution.
In Figure 3a, a nano wheat grain-like structure caught in a nanopore spider web-like structure is presented, which forms on the surface at 72 h holding time and at low NaOH concentration of 0.05 M.
Increasing the solution concentration at 0.1 M (Figure 3b) the wheat grain-like structure became the only surface morphology.
The grains have a random alignment and nano/microporous structures have formed between them.
POCU/993/6/13/153437; and by a grant of the Ministry of Research, Innovation and Digitization, CNCS‐UEFISCDI, project number PN‐III‐P1‐1.1‐TE‐2021‐0963, within PNCDI III, with contract number TE13/2022 (DD‐CyT).

It can be seen from Fig. (2) (b), (d) and (e) that the grain size of three alloys sheet are almost the same, but the second-phases in the matrix of three alloys are obviously different from each other as shown in Fig. (2) (a), (c) and (e).
There are many rod like second-phases in the matrix of 6016 and 6181 alloys which are remained constituent consisting of AlMnFeSi [10, 11], and the number of the them in the 6016 alloy is much larger than that in the 6181 alloy, while there are almost no second-phases in the pure aluminum.
Whereas, it can be concluded from Fig. 1 and Fig. 2 that the recrystallization texture and the grain size of three aluminum alloys sheets are alike, except that the number of second-phases in the matrix of the three alloys are obviously different from each other.
It seems to be inconsistent with the general consideration that the plastic strain ratio r value is mainly influenced by the texture and the grain orientation of alloy sheet [1-4].
Based on the principle that the microstructures determine the properties of alloy, it can be deduced that the large number of second-phases in the matrix of 6016 and 6181 alloys (shown in Fig. 2(a) and Fig. 2(c)) is the just factor which resulted in the discrepancy as mentioned before.

Especially metal-free devices are of interest, because of the increasing number of patients sensitized to metals.
The SHA platelet-shaped grains homogenously dispersed in the ceramic composite microstructure provide an additional barrier to crack propagation.
The biological safety of both materials has been assessed in vitro, using a number of different test parameters.
This material is obtained by Liquid Phase Sintering (LPS) followed by a post-sintering treatment that allow the development of rod-like Si3N4 grains with length / thickness ratio 5 to 10, joined to a crystalline secondary phase and by an amorphous (glassy) grain boundary phase.
The elongated grains have a toughening effect due to crack bridging and deflection [78].

This is due to the fact that with decreasing crystallite size the dislocation activity inside grains decreases and, therefore, the strength and hardness increase up to the "strongest size" [18] where the grain boundary shear, that makes increasing contributions to the total strain with decreasing size, leads again to softening [11,19].
There is no dislocation activity in the grains of the nc-TmN/a-Si3N4 nanocomposites [20,21] which deform only elastically, whereas the plastic deformation is carried entirely by shear in grain boundaries [22].
Therefore, their hardness depends on the quality and purity of the grain boundaries achieved during their preparation [2].
The number 1971 in the parentheses is related to the electron density of a non-polar covalent bond between the neighbouring atoms and the second term 220·λ describes its weakening by the polarity [23,24].
The superhard nanocomposite coatings are being used for a large number of industrial applications in cutting, forming, stamping and other operations and their applications are expected to grow fast in the near future.