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KCl-NaCl/1 KCl-NaCl/2 CaCl2/1 CaCl2/2 NaCl/1 Fig.2: X-ray patterns of all samples after drying process It is evident from the images taken by the scanning electron microscopy that the resulting products are rough-grained, perfectly formed corpuscular developed prismatic alpha plaster particles, only in the case of 32% CaCl2 solution grains are they evidently more subtle.
Grains from CaCl2 solution were more subtle because of faster reaction.
Only in the case of 32% CaCl2 solution grains of hemihydrate are evidently more subtle.
Acknowledgements This work was financially supported by project number: FAST-S-12-25/1671.
Registration number CZ.1.07/2.3.00/20.0111 References [1] FRIDRICHOVÁ, M.; ZLÁMAL, P.: Preparation of alpha-gypsum by contact-free method.

In the samples mixed with solid carbon a continuous layer of carbides formed on the surface of the spinel grains.
Introduction Stainless steel plays a significant role for civilization, as an increasing number of materials is consumed by the growing population of the world.
Reduction on the surface of the ore grains and, therefore, formation of the metal particles did not occur (Figure 5, a, spectrum 1), since CO gas is not a strong reducing agent, whereas in chromospinelide, iron and chromium are bound in one crystal lattice.
On the surface of the ore grains, there was no reduction and separation of the metal particles.
In samples reduced by mixture of CO gas with solid carbon, a continuous layer of carbides formed on the surface of the spinel grains.

A metallographic analysis of the grain structure of the samples in a deformed state and after annealing performed.
Table 1 The chemical composition of the alloys, mass % Alloy number Al Ce La Zr Fe Si 1 99.4 – – 0.30 0.20 0.10 2 Basis 0.5 – – – – 3 Basis 4.58 2.48 – 0.22 0.10 To assess the change in the properties of the rods after heating, annealing was performed at temperatures of 230-450 ºС.
The nature of the grain distribution after deformation and annealing was revealed by oxidizing the surface of the sections in the Barker reagent at the Struers LectroPol–5 electrolytic polishing and etching unit.
a b c d e f Spectrum Al Zr Fe Si Spectrum 1 83.8 – 11.8 4.4 Spectrum 2 87.0 – 10.2 2.9 Spectrum 3 99.6 0.4 – – Fig. 3 Microstructure of rods from alloy 1: a, b – SEM of rods and grain structure after IRE; c, d, e, f – annealing at 230, 300, 400, 450 °С The microstructure of alloy 1 rods consists of an aluminum matrix and AlFeSi phases, zirconium is completely dissolved in the solid solution, no primary Al3Zr crystals were found in the alloy structure (Fig. 3 a).
a b c d e f Spectrum Al Ce La Fe Spectrum 1 84.0 10.3 5.5 0.2 Spectrum 2 65.5 22.6 11.5 0.4 Spectrum 3 90.5 6.0 3.4 – Fig. 5 Microstructure of rods from alloy 3: a, b – SEM of rods and grain structure after IRE; c, d, e, f – annealing at 230, 300, 400, 450 °С An analysis of the grain distribution in the structure of the samples showed that, after annealing at 230-400 °C and holding for 1 hour, the rods of alloy 1 retain a fibrous deformed structure, after annealing at 450 °C and 10 hours the bar structure has a crystallized structure (Fig. 3 f), which indicates a loss of strength (table 2).

The migration and enrichment of iron atoms provide material source for recrystallization and grain growth of crack healing zone.
Meanwhile, a large number of ferrite grains gradually enriched near the crack healing zone.
As shown in Fig. 3a, a white band appeared through the whole crack, which was composed of a great deal of fine equiaxed ferrite grains.
After healing treatment at 1200°C for 60 min, the equiaxed ferrite grain in the white band grew up into chain-like ferrite.
The migration and enrichment of iron atoms provided material source for the formation and growth of recrystallized grains.

Yang et al. applied PMF during the solidification of Mg-Al-Zn alloy and Al-Cu alloy, and the primary α-Mg grain and eutectic structure were refined [4,5].
In contrast, the microstructure of Mg93Zn6Y alloy treated by PMF which consists of majority of primary α-Mg grains with fine rosette-like morphology, as shown in Fig.2 (b), and the average diameter of primary α-Mg grains were about 102μm.
In the case of PMF, the initial solidified many nuclei forming on the wall of the mold in a heterogeneous nucleation pattern were easily broken off by forced convection and would be transported into the entire liquid metal [4].Thus, the number of nuclei in the melt was increased.
It can contribute to increasing the rate of heat transfer and the removal of liquid superheat [7], which decreased the likelihood of remelting of initial solid grains.
Moreover, fragmentation, nucleation and growth could happen within the entire melt, which gave rise to the refinement of grains throughout the bulk liquid.

The average grain size was measured to be ~100 µm for aluminium, and 10-40 µm for copper and silver.
The number of ECAE passes was limited to 3.
The main difference appears in terms of relative intensity of components, and further variation in intensity on increasing the number of passes.
In simple shear, grains near the A1* component arise by slip mechanism as well as by twinning.
In silver, as a result of ECAE deformation, texture strengthens further with increase in the number of passes.

In addition, under agitation, the crystallization fraction of sample increased from 71% to 88%, and the average grain size was reduced 23%.
However, due to Qn(mAl) (n is the number of bridging oxygen (BO) atoms in the silicate groups, and m is the number of neighbor aluminate groups) species were included in the AlO4 unit of aluminosilicate, it still could not be decided that which species was the ultimate reason for the shear-thinning behavior.
It could be seen that the grain size of sample obtained under agitation was smaller than that of sample obtained without agitation.
While, the change of crystal density was exactly opposite with that of the grain size.
(3) The crystallization fraction of sample was increased and the grain size was decreased with agitation.

As a rule, the size of grains/subgrains after SPD makes 100-300 nm [1].
The absolute variation of deformation zone surface area can be represented as: , (6) where nd, b and lav – correspondingly, number of dislocations, Burgers vector and dislocation average length.
Raab, Influence of the scale factor on grain refinement during severe plastic deformation // Press forging.
Zhu, Long-length ultrafine-grained titanium rods processed by ECAP-Conform, Mater.
[7] Ultrafine-grained titanium for medical application/ R.Z.

Precipitated phase in steel keeps the austenitic grain growth and delays high temperature deformation austenite recrystallization.
The finishing temperature of the experimental steel was 800 ℃, fine ferrite grains was obtained through flatting the austenitic grains along the rolling direction and forming a large number of deformation zones in grains to greatly increase the nucleation points and crystal nucleus generate energy during the phase transformation of austenite to ferrite [7].
High density of dislocations and tiny carbonitride were finely distributed in grains.
The plenty of tiny spherical NbC particles about 30 nm precipitated in the grains and sub-grains.
The crack propagation was difficult due to the presence of a great number of obstructions per unit length of acicular ferrite.

The estimated value of grain sizes of the samples are 29 nm for sample annealed for 30 minutes, and 43 nm for sample annealed for 1 hour.
The films show nanoparticles ZnO with large number of grain boundaries.
Measured from the micrographs, the average of the grain size for sample annealed for 1 hour is bigger than sample annealed for 30 minutes, which is agreeable with the calculation from the XRD result.
This is due to the grains that become more uniform and denser [11] with the increasing of annealing time.
The adsorption of oxygen in the grain boundaries during the annealing process will cause the carrier concentration to be trapped and though increase the number of electrons in the ZnO film [15].