Search results

This paper considers the oxidation of a number of nickel containing Fe based alloys of varying compositions, including stainless steel.
This makes the structure of the scale more complex as the number of phases present increases.
Although this Ni seems to be segregated to grain boundary regions, closer examination (Fig. 3) revealed that the Ni is located in regions adjacent to the grain boundaries.
It was found that, as expected, the internal oxide is situated at the high angle grain boundaries and not the twin boundaries, which are clearly visible within the grains shown in the IQ map.
Iron from the substrate below the nickel-enriched layer and in the area surrounding the grain boundary will diffuse outwards preferentially along grain boundaries where it will meet inwardly diffusing oxygen.

The number of hydrogen atoms in the NDSR or HLSAD, per the dislocation length of b, can be described [2] as nH⊥ ≈ (CΣ - C) / ρ⊥ b2
In this connection, it ought to be emphasized that in a number of works, for instance [18,22,41, 42] some inadequate concept is used.
For a number of cases, this results [1] in reasonable values of ∆HB ≈ 40-20 kJ mol-1 and, correspondingly, reasonable values of K⊥ (increasing with reduction of CΣ).
Consideration of the Mössbauer and Diffusion Data on CLNS of Fe at Grain Boundaries in Al.
Numerous surface nodules, made of virtually pure nickel, were visible within the grains.

Birmingham parameters were used to characterize the performances of grinding wheel, in items of grain density, grain shape and grain sharpness.
Density of abrasive grains.
The Birmingham parameter of Sds is the number of summits of a unit sampling area.
Its expression is: number of summits ( 1)( 1) Sds M N x y      (2) where M and N are the number of data points in x and y directions; Δx and Δy are the sampling interval in x and y directions.
With a smaller sampling interval, a larger number of peaks will be counted.

The average grain size, grain size distribution and volume fraction of dynamic recrystallization were taken into account.
Lower dislocation density and distortion energy with smaller deformation leads to a lower number of nucleation on the blade rabbet.
However, the velocity of nucleation is faster compared with that of grain growth so that the grain is finer.
The grain size number of dynamic recrystallization in the middle of blade body is 9~10 and the grain size number in the leading and back edge of blade body is 10~11.
The size number of recrystallized grains in the blade rabbet and body are 8 and 9~10 respectively according to the experimental data.

Simulation model Grain growth model.
Thus a relation can be obtained between grain size (Lmax) at the highest sintering pressure, σmax, and grain size (Lσ) at an arbitrary sintering pressure σ: (7) where kP is pressure factor which reflects the possibility of grain growth.
Lattice sites having the identical Q number are considered as a grain, and a grain boundary segment is defined to lie between sites of different Q number.
In order to study the effect of sintering pressure on microstructure evolution, the pressure factor, kp, is coupled into MC Potts model, the probability of switching the orientation number at a lattice site is determined by evaluating the energy change ΔE [8] during reorientation.
It can be found that the mean grain size of matrix phase increases with an increment in sintering pressure in the same simulation time, and the number of nano-particles entrapped into matrix grains increases accordingly, indicating that higher sintering pressure is beneficial to grain growth and the formation of intragranular-type microstructure.

When a grain-boundary is exposed to a high, completely elastic mechanical stress σ, an embrittling species can penetrate it by grain-boundary diffusion.
On the other hand, if the crack tip iss surrounded by a high number of CSL grain boundaries, it should be possible to reduce the susceptibility to cracking by dynamic embrittlement [8,13].
As represented in the crack velocity vs. stress-intensity factor plot in Fig. 7b, crack propagation along a random high-angle grain ductile-fractured grain boundary 10µm boundary is by two orders of magnitude faster than along a special symmetrical Σ5 grain boundary.
Under the influence of a high elastic tensile stress acting normal to grain-boundary planes, an embrittling species can diffuse into the grain boundaries and lower the interfacial cohesion.
Small-angle grain boundaries or special grain boundaries with a high fraction of coincident lattice sites between the neighboring grains seem to exhibit a particularly low diffusivity of the embrittling element; i.e., they have a high resistance to dynamic embrittlement.

Watershed analysis on AFM images show that the numbers of grain boundaries in Ni/ITO are reduced when annealing temperature is increased to higher temperatures.
Annealing Temperature (°C) Root Mean Square, RMS (nm) Peak to Valley, P-V (nm) Number of Grain Boundaries, N Thickness (nm) 450 1.978 25.083 83 2.898 500 1.887 30.482 80 3.491 550 2.134 22.918 81 3.863 600 2.598 59.115 55 4.569 Fig. 2, Surface roughness and peak-to-valley of Ni/ITO for various annealing temperatures scan by AFM.
Figure 3 shows the grain boundaries of the samples using watershed method.
The numbers in the images indicate the total grain boundaries on the surface of the annealing samples.
The total number of grain boundaries decrease when the annealing temperature are increased.

The results show that the yield strength of hot-rolled ribbed wire rod is 510MPa, the tensile strength is 622MPa, and the elongation is 23.35%, but the content of Mn can be decreased 58.13%, the content of Si can be decreased 67.50% compared with the national standard upper limit value in HRB400; The grain size scale of edge microstructure is 9.0 at the 1# flying shear in the rolling process, the grain size scale of core microstructure is 8.5, and the edge microstructure of hot-rolled ribbed wire rod after rolling is the tempered sorbite, the grain size scale is 13.5, the core microstructure is the ferrite-pearlite, the grain size scale is 12.0, and the depth of hardening is 0.50mm.
Along with the rapid development of national economy, the consumption of Hot-rolled ribbed wire rod has increased sharply, and the requirements of comprehensive performance are also more and more high[4-5], but the energy and transportation resources are limited in China, so it can’t meet the dramatic growth of steel production capacity, we must purchase a large number of foreign resources, so it lead to the global steel production of raw material supply tension, and the prices are soaring, which will directly endanger the health of the steel industry sustainable development.
Fig.2 The stress-strain curve of hot-rolled ribbed wire rod Table 2 The mechanical properties results Sample Yield strength (MPa) Tensile strength (MPa) Elongation (%) 01 500 625 24.58 02 522 624 22.16 03 508 616 23.32 Average Value 510 622 23.35 Table 3 The measured chemical composition of material Material Chemical compositionWt, (%) C Mn Si P S Microalloy Nb, V, Ti National standard of HRB400 ≤0.25 ≤1.60 ≤0.80 ≤0.045 ≤0.045 Microscale Sample 0.22 0.67 0.26 0.019 0.023 - The microstrucucture morphology at 1#-flying shear in the rolling process as shown in Fig.3, the grain size scale of edge microstructure is 9.0, the grain size scale of core microstructure is 8.5, and the microstrucucture morphology of hot-rolled ribbed wire rod after rolling as shown in Fig.4, the edge microstructure is the tempered sorbite, the grain size scale is 13.5, the core microstructure is the ferrite-pearlite, the grain size scale is 12.0, and the depth of hardening is 0.50mm.
(a)edge (b)core Fig.3 The microstrucucture morphology at 1#-flying shear (a)edge (b)core Fig.4 The microstrucucture morphology of products Summary Through optimizing the rolling process, and the yield strength of hot-rolled ribbed wire rod is 510MPa, the tensile strength is 622MPa, and the elongation is 23.35%, but the content of Mn can be decreased 58.13%, the content of Si can be decreased 67.50% compared with the national standard upper limit value in HRB400, and there is no microalloying elements; The grain size scale of edge microstructure is 9.0 at the 1# flying shear in the rolling process, the grain size scale of core microstructure is 8.5, and the edge microstructure of hot-rolled ribbed wire rod after rolling is the tempered sorbite, the grain size scale is 13.5, the core microstructure is the ferrite-pearlite, the grain size scale is 12.0, and the depth of hardening is 0.50mm.
Wen: Ultra fine grain steel (Metallurgical industry press, Beijing 2003)

The principle of emerging two-dimensional Voronoi crystalline grain structure is: (1) in certain area, some geometry points are sown some points of geometry to define the grain embryo at random.
According to the grade characteristic of crystalline grains in national standard GB/T6394-2002，when grade of crystalline grain is offered，for the calculating formula: (1) we can obtain density of crystalline grains, that is number of crystalline grains on an area equaling to 1,by which we can simulate polycrystal models through Voronoi algorithm.
Fig.4.Metallographic picture of aluminum alloy The shape and area of the crystalline grain, as the visualized indices of the character, can reflect detailed geometry view of material structure; therefore, the side number and area of the every polygon under different grades from 2 to 4 of crystalline grain are statistical analyzed.
Mean value of the side number of every grain under different grades of crystalline grain is shown in Table 1.
Table 1.Statistic of crystalline grain polygon Project Grade 2 Grade 3 Grade 4 Mean value 5.314 5.322 5.346 Theory value 5.148 Above all ,we can conclude that the meso-scale model based on Voronoi algorithm has met the metallurgy principle through the mathematical information and geometric simulation，and have good consistency with actual structure in main characters such as grain shape, side number, area, etc, which can offer the good structural form for meso-scale calculating.

Furthermore, the grain orientation effects of BNTV-y ceramics on their piezoelectric properties are discussed using the grain-oriented ceramics prepared by the hot forging (HF) method.
Grain-oriented samples were prepared by the hot-forging method (HF).
RESULTS AND DISCUSSION X-ray diffraction patterns for (OF) BIT-Nd, BIT-V and BNTV ceramics show single phase of bismuth layer structured compounds with the layer number, m=3.
It is considered that these small grains prevent large grains from being orienting.
On the other hand, the number of small grains of the (HF) BNTV-y0.25 ceramic� shown in (a) are fewer than those of the (HF) BNTV-y0.75 ceramic.