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Furthermore, because of high temperatures required to melt steel obtaining coarse-grain materials with poor mechanical properties is practically unavoidable.
The grain size in austenite steels cannot be reduced by heat treatment, so multiple pressure processing which eventually leads to an increase in duration of the process cycle, growth of energy consumption and rise in the material price is needed.
Distribution of components in the particles Fe-18Cr-8Ni-12Mn, after MA synthesis for 3,5 hour: a - the structure of the investigated area; b - Fe; c - Cr; d - Mn; e - Ni; f - spot chemical analysis results In order to explain the alloying mechanisms of materials in the process of MA, a number of models describing the processes of forming metastable solid solutions and compounds are proposed.
Then, the diffusion of alloying elements from the border into the grain core causes the formation of mixed solid solutions.
These are interstitial diffusion at the moment of pulsed mechanical impacts and diffusion along the crystal lattice defects (dislocations, vacancies, grain boundaries, etc.).

This fact is a challenge for producers of brass products and research in recent years shows that this challenge was accepted by significant number of research scientists in the field of metallurgy.
Selenium is present as a copper/zinc/selenide phase, which segregates at grain boundaries.
Like lead, bismuth is essentially insoluble in brass (see Fig. 2) and is found as discrete particles in matrix and grain boundaries [7].
La Fontaine et. al found that very promising element preventing the bismuth segregation at the grain boundaries is tin.
The excess concentration of tin at the grain boundaries due to coring prevents segregation of bismuth [11].

The grains are refined and the toughness can be improved greatly.
In the study, a large number of trial experiments were conducted to identify the feasible testing conditions for the hot compressed AZ31B magnesium alloy weld metal region under immersion conditions.
The grain of HAZ zone is coarse, and easily corroded.
There are some grains of a-phase being corroded because of the lack of b- phases.
From the weld zone morphology, the grain of weld zone is refined because of the hot compression, and quite lots of b-Mg17Al12 phase particles distribute continually along the grain boundary.

It creates a number of important engineering properties in soils which include improved strength [2].
The sample portion that passed through 75µm sieve was conducted to hydrometer test in order to determine the percentage of different grain sizes contained within a soil.
According to the suitability of lime stabilization for soils of different grain size and plasticity, fine-grained materials must more than 25% passing passes sieve No.200 (0.075mm) and plastic index is greater than 10.
Based on the Fig. 1, it shows that the soil is fine-grained and more than 25% of soil fraction passes sieve No.200 (0.075mm).
Based on the data analysis, the following are the conclusions; • The soil for this study is fine-grained and more than 50% of soil fraction passes sieve No.200 (0.075mm) and the plastic index is higher than 10, therefore the soil is suitable for lime stabilization

The CVD diamond film (Fig.1a) presents a rugged surface covered by well-faceted diamond crystallites with grain size of 2~3 µm, most of which had sharp octahedral shape and exhibit <111> or <100> crystallographic orientations.
No discernable diamond grains were observed.
The slight shift from the 1332 cm-1 in wave number was owing to either a compressive residual stress and/or a convolution of the microcrystalline domain size.
The broader peak near 1580 cm-1 (G band) can be correlated to the graphite or amorphous carbon phase existed in the grain boundary area.
Conclusion The SEM study presented a continuous layer of diamond films, with grain size of 2-3µm, was uniformly deposited on the surface of cutting tools.

Gulenc etc have studied 304L stainless steel with MIG process in different parameters,and its conclusion that though MIG process has many advantages,the negative effects were the HAZ grain coarsening and smooth transitional droplet is hard to obtain[5].
Fig. 1 Surface morphology of stainless steel vehicle body with traditional process Apparently,GMAW welding surface morphology showed that the welding quality is not ideal.Defects including air hole and overheat were found in welded joint.So it is difficult to achieve the sound weld with acceptable weld strength of the welded joints and smooth surface morphology.Welding quality become a key problem which should be resolved.To the problem,Welding process have to be improved.By a large number of investigation and study,GMAW process is replaced by cold metal transfer(CMT) process.
Due to a very small heat input from the CMT welding,the distortion was not observed in the weld,and the HAZ zone was narrow comparing with traditional fusion welding.In the macroscopic view,as shown in Fig. 5(a) .The welding line of weld metal and base metal was a stretch of v-shaped contour.The crystallizing morphology on the weld seam was equiaxed grains and dendrites and that on the fusion area were columnar crystals.Crystals on the weld appeared in growth to the weld center,and coarse grain size of austenite in HAZ was relatively uniform.
Further studies on CMT welding joint microstructure morphology by using SEM.As shown in Fig. 5(b),Microstructure morphology is more distinct and the heterogeneity of grain size nearby the fusion line is obvious.Base metal grain with dimensions of 20 microns to 40 microns.The fusion zone is only about 150 microns width due to small heat input from the CMT welding.

Grains of alloys except for Alloy A are surrounded by dark carbides, and the grains are composed of bright and gray regions, each of which corresponds to Ni solid solution γ and Ni3Al γ', respectively.
The grain size of matrix phase and dispersed carbides ranges 100 - 200 µm and 5 - 20 µm, respectively, while large carbides are found in Alloy D.
It is obvious that with increasing carbon concentration, fraction of high hardness values, i.e., numbers of the position which show high hardness, increases as was reported by Tian et al.[7].
The strength of Alloy A is about half of the reported value for IC218 [12], due to the difference of grain size.
However, the uniform plastic deformation of metallic grains during compression test might be suppressed by neighboring carbides in the manner of the metal-matrix composite with hard particles.

A number of intensified sintering methods such as hot-press sintering, activator-diffusion intensified sintering, liquid-phase intensified sintering, self-propagating reaction sintering, microwave sintering, and spark plasma sintering, are currently used to achieve lower sintering temperature, higher sintering rate, or improved properties of sintered materials [5-8].
Magnification - 500 On the basis of structural observations, it is remarkable that the finest structure can be observed for 316LHD sample, while the biggest grains were found for 434LHC samples with ferritic structure.
The highest strength values were observed for 316LHD steel (Rm=752 MPa), which might be attributed to its lower porosity and impact of carbon and molybdenum on solution hardening in austenite grains (Fig. 3A).
The structural tests and microhardness tests revealed existence of two, differently etched ferrite types of grains in 434LHC steel structure: pale - with hardness of 163 HV and dark ones with hardness of 368 HV.
This fact indicates existence, except for ferrite grains, of martensite grains i.e. hard and brittle phase (Fig. 3B).

Thanks to the introduction of electromagnetic or mechanical stirring, the broken dendrite arms would act as new nucleation sites leading to the morphology of spherical primary grains surrounded by eutectic phases.
They draw a conclusion that optimized heat treatment time were related to grain size.
And then, the samples were polished for measuring the grain size and the change of eutectic silicon particles.
For better resolution of the grains, the specimens were etched by Keller reagent for 10 seconds.
The dense-distributed silicon firstly separated into numbers of single particles.

It is proposed to simulate the behavior of one grain with different initial densities and different initial orientations.
The simulation of the behavior of a grain in highly symmetrical situation leads to activation of several systems.
Fig 4: Macroscopic stress-strain curves comparing the stress and deformation of two grains with different orientations.
This is probably more in line with the reality of a grain under a constrained field when it must also accommodate the deformation of its neighbors.
The type of finite element formulation used is C3D8I and the number of elements in the thickness is fixed to 6.