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The dislocation of crack tip,grain boundaries and different grain orientations have great influence on the path of crack growth, which can make cracks bending.
As shown in fig. 1, a number of small black spots dispersed and distrubuited in A7075 alloy with a bit gray in the grain, which may be caused by oxide inclusion or precipitation phase of grains and grain boundries.
Meanwhile, there is a deformation in the grain boundary junction, even appearing parts of the grain layer fracture.
In order to achieve a balance of free energy in the fatigue process, cracks may be initiated at grain boundaries or junction of grain and matrix.
When fatigue cyclic number was 4000 times (6c), the primary crack completely formed with the secondary micro-cracks initiation in the peripheral.

But among them, vertical centrifugal casting technology turns more and more into a fruitful method for its low production cost in producing a great number of special castings [2].
The casting loaded on a vertical centrifugal unit of the furnace has been revolved prior to the casting experiment in an anti-clockwise direction with rotation number from 0 rpm to 280rpm.
The microstructures of castings produced at 160rpm and 280rpm are all equiaxed grains, furthermore the grain sizes at the sharp corner of the wedge casting are finer for the bigger cooling rates at these parts.
The grain size changes greatly with different wall thickness of the casting.
Conclusions (1) The crystals near the outer surface of the wedge casting produced at the gravity field are columnar grains, while the grains produced at centrifugal field are all equiaxed grains.

The presence of grain boundary particles leads to enhanced grain stability at elevated temperatures.
Therefore, the deformation temperature is kept as low as possible to minimise grain growth.
All alloys show enhanced grain stability during heat treatments due to the presence of the grain boundary particles.
The fatigue limit is reduced by 10% due to weakening of the grain boundaries.
The work on Ti-6-4 alloy has been supported by the Arbeitsgemeinschaft industrieller Forschungsvereinigungen (AiF), Project Number IGF 253 ZN.

The novelty of the approach stems from incorporating an incubation period in the equations describing the progress of dislocation density with strain; beyond such incubation dislocation free grains form.
During hot rolling, DRX is employed for engineering grain size which further influences mechanical properties via the Hall-Petch effect [1].
At low temperatures, DRX is fundamental in attaining ultra-fine grained and nanostructured ultra-strong pearlitic wire (reaching 5 GPA strength) subject to severe plastic deformation [2].
• C: is the dislocation recovery term; fDRX = Nnucl Ngrowth − 1 = exp ( 6 κckBT ([(1 + x)N]−1T∆S | {z } i + 2xl∗ bκc ∆Gsys | {z } ii − λ 2µb3 | {z } iii )) − 1 depends on the difference between the number of subgrains with sufficient energy for grain nucleation Nnucl (from whom grain growth occurs) and the number of growing grains Ngrowth, divided by Ngrowth. κc is a variable that relates the dislocation density to the formation of cells [8].
Term i incorporates the energy dissipation related to grain boundary motion, and is expressed in terms of the entropy for disocation glide; term ii accounts for the solute/grain boundary interactions; and term iii quantifies the energy required to initiate grain growth.

At two deformation temperatures, grains were refined at more or less similar size reduction rate as a function of number of passes.
This results in a steady-state in the grain-size refinement at very high strain values.
Annealing of billets resulted in a grain size of about 80 µm (called the ‘reference’ sample).
(c) Variation of YS with number of ECAP passes.
This could be the strain beyond which grains started rotating during the ECAP processing.

The infrared transmittance in the wave numbers of 1500-4000 cm-1 is less than 15 %.
Experimental procedure Ti powder (< 75 μm average grain size, ≥ 99.0 wt% purity), Si powder (< 75 μm average grain size, ≥ 99.9 wt% purity), B4C powder (< 154 μm average grain size, ≥ 99.0 wt% purity) and C powder (<75 μm average grain size, ≥ 99.0 wt% purity) were put in constant temperature drying oven at 120°C for 2 h, and mixed respectively according to the following chemical reactive equations
TiSi2 has been crystallized finally with a grain diameter of about 100-200 nm and distributed on the grain boundary of Ti3SiC2 grain due to its lower melting point (1480 °C), which has been avoided in service parts for the heat.
It can be seen that grains are in irregular shape, and the average grains size are under 350 nm.
However, the light transmittance of Sample B is dropped to below 15 % in 1500-4000 wave numbers/cm, and that of Sample C is dropped to 5%-11% in 1500-4000 wave numbers/cm.

The huge number of memories required to calculate the view factors for each surface cell against others makes it extremely complicated and difficult for the heat radiation calculation in directional solidification.
Fig. 5 Simulated grain evolution progress.
The simulated results show that a great number of tiny grains appeared at the bottom of the blade shortly after the beginning of the withdrawal progress.
When growing upwards, those grains with a better favorable crystal growth direction, which had a small angle with the heat flux direction, got larger chances to grow bigger and finally grew into several dozen of large columnar grains.
This shows the competitive grain growth progress during directional solidification, and reproduces the formation of the typical large columnar grains in the directional solidified turbine blade castings.

"Chinese Says" food safety in fact, only including food grain, soybean and potato, is Grain Security.
The Contribution of Irrigation on Grain Security in China.
The Sown Area of Grain and Irrigation Area Situation.
In the course of the development of China's agriculture efficient water use techniques, these departments have a number of joint researches, joint implementation, making many high - level results effectively promoting the development of china's agriculture efficient water use.
Relevant state departments should open up grain prices, according to the law of the market economy, completely open up grain prices, and implement grain subsidy for low - income urban residents.

Results and Discussion Analysis of the evolution of the microstructure showed that low-alloy steel grade 18G2S in the initial state (after homogenizing annealing) has a perlite-cementite structure, secondary cementite is located along the grain boundaries (Figure 1), the average grain size is 25 microns.
Despite the high density of dislocations, a large number of dislocation-free subgrains are also observed (Figure 2a).
The detected recrystallized grains differ not only in the absence of dislocations in the grain body, but also in the close-to-equilibrium structure of the disorientation boundaries, as evidenced by the weak banded electron-microscopic contrast at these boundaries.
Based on the statistically processed results of mechanical tests, the average value of properties was determined (where Xi is the result of a separate test, n is the number of tests) and graphs of the dependence of strength and plastic properties on the number of passes were constructed.
Perezhogin, Grain refinement, texture, and mechanical properties of a magnesium alloy after radial-shear rolling, Journal of Alloys and Compounds. 774 (2019) 969-979

Lead has high atomic mass number Z and high density.
Tungsten, which has better shielding properties than lead because of its high Z (atomic mass number), is a material that is difficult to machine or cast, the melting point being as high as 3387°C[4].
Smaller mfp values is an indication of higher number of interaction of the incident radiation beam with the atoms of the sample(s) being tested.
The high number of interaction as the distance between successive collisions reduces resulted in large attenuation values.
Grain size and grain size distribution of the hard component in the tested sample has great impact on the overall microhardness value, small grain size creates more regions of stress concentrations around the hard component and increases the probability of hit of the indenter to the W particles within the brass matrix and consequently gives higher microhardness value.