Search results

Table 1 Austenite grain size and pearlite size of industrial U75V Sample number Steel grade Average grain size (μm) Austenite grain size grade (grade) 11# U75V 11.704 9.0 51# U75V 13.481 9.5 Fig. 1 Austenite grain size of 11# Fig. 2 Austenite grain size of 51# The austenite grain size of industrial U75V rail was 9.0 grade by means of sampling, semi-quenching, processing and inspection analysis. 2 High Temperatures Confocal The variation of austenite grain size of high carbon rail steel had been visually revealed by using different insulation temperatures for U75V rail specimens.
Table 2 High temperature confocal test results of U75V rail specimens Number Steel grade Insulation temperature (℃) holding time (s) Austenite grain size (μm) Austenite grain size (grade) 1 U75V 1300 180 164 2.5 2 U75V 1200 180 137 3.0 3 U75V 1100 180 146 2.5 4 U75V 1000 180 117 3.5 5 U75V 900 180 30 7.0 1200℃, 180s 1300℃, 180s 1000℃，180s 1100℃，180s Figure 3 1 # Metallographic photograph Figure 4 2#Metallographic photograph Figure 5 3 #Metallographic photograph Figure 6 4 #Metallographic photograph 900℃，180s Figure 7 5# Metallographic photograph The formation process of austenite included nucleation, growth, dissolution of Fe3C and homogenization of A.
The growth of austenite grain is carried out by grain boundary migration.
Small grains are shrinking, large grains are growing, then large grains eat small grains.
Table 3 Rail heating process and corresponding austenite grain size in laboratory Sample number Steel grade Insulation temperature (℃) holding time (min) Austenite grain size (grade) 1 U75V 900 30 6.5 2 U75V 1000 30 4.5 3 U75V 1100 30 3.5 4 U75V 1200 30 2.0 5 U75V 1300 30 0.5 6 U75V 1000 10 6.0 7 U75V 1000 50 5.5 　 Figure 8 Grain morphology of 1#　 Figure 9 Grain morphology of 2# 　 Figure 10 Grain morphology of 3#　 Figure 11 Grain morphology of 4# Figure 12 Grain morphology of 5# Figure 13 Grain morphology　of 6# 　Figure14 Grain morphology of 7# Temperature (℃) Figure 15 Effect of holding temperature on austenite grain size grade Figure 16 Effect of holding time on austenite grain size It can be seen from Figure15 that austenite grain size grade of U75V rail steel decreases and austenite grain gradually coarsens when the holding temperature rises from 900 to 1300.

Accordingly, two numbers are given in Table 2.
Two numbers are given in table 1 because the determination of GBC is ambiguous.
Table 2 Number of GBC with and without a precipitate.
Table 3 Number of precipitates at various types of GBCs.
Type Total number of GBCs examined Number of GBCs with precipitate Number of GBCs without precipitate Fraction with precipitate A 10 7 3 70% B1 5 2 3 40% B2 4 1 3 25% C1 4 0 4 0% C2 1 0 1 0% D 3 1 2 33% Total 27 11 16 41%

The Flow Behavior of Ultrafine-Grained Materials Terence G.
The processing of metals by SPD Ultrafine-grained materials are defined formally as polycrystalline metals having average grain sizes less than ~1 mm [10].
This means that UFG metals incorporate both submicrometer grain sizes of 100 to 1000 nm and true nanostructured materials where the grain size is <100 nm.
It is also apparent that the yield stresses increase with increasing numbers of ECAP passes.
Thus, the yield stress is lower after 1p than for the as-received material and it continues to decrease with increasing numbers of passes.

As usual in the physical models aimed at a quantitative description of material transformations, there are a number of constants to be determined empirically [9].
A considerable portion of the volume is occupied by the largest austenite grains though their relative number is very small.
The distribution of grain numbers over grain size is recalculated into the distribution of the normalized volume over the grain size: ∫ ∞ ⋅ ⋅ = 0 3 3 )( 6 )( 6)( auauNau auNau auV dDDD DD D ρ π ρ π ρ
The integral distribution function Fv(Dau) shows that roughly 24% of the volume is occupied by the large grains with sizes larger than (+3 σD), whereas the number fraction of these large grains is negligible (1.5%).
suggestion that grain volume distribution is more meaningful than the number distribution.

Ultra Fine-grained 6wt% Manganese TRIP Steel Seawoong Lee1, a , Kyooyoung Lee2, b , B.
An ultra-fine grained microstructure with a grain size less than 1μm was obtained.
Fig, 6 shows a stem image which is used to calculate mean grain diameter.Assuming the total volume fraction of each grain was not changed by the annealing, the average grain diameter was calculated by counting the number of grain boundaries intercepted by a straight line across stem micrographs.
Using equation (1) in the transverse and normal direction :     xM L L (1) Annealing temperature(℃) Fraction by XRD [%] Fraction by Magnetic saturation [%] 640 20 23 660 15 16 680 30 33 Where M is magnification, L is the total line length in calculated direction andx is number of points intercept grain boundaries, the average grain diameter was calculated.
An ultra fine-grained microstructure with grain sizes of 0.1 to 0.2μm was achieved by a short, low temperature isothermal hold.

An original method is used for the construction of initial structures with GBs containing different numbers of EGBDs.
Taking the orientation of grain 1 as a reference, grains 3 and 4 are rotated to angles ±20° to form a symmetric high-angle tilt GB between them.
As an example, consider a deformation of grains 3 and 4.
The grain size of nanocrystals was set equal to 15 nm.
This stress induces oscillating shear stresses on the slip planes of grains 3 and 4 and zero stresses on the slip planes of grains 1 and 2.

At around 400℃ cube grains penetrated to the thickness, non cube grains being formed.
After final annealing up to 540℃ the number of Laue spots decreased, suggesting that grain growth occurred among TD-rotated cube grains.
Decrease in number of grain are from approximately 20 at 320℃ to 1 at 540℃ for {311} spots.
At 295℃ the number of fine dots in the streaks increased and continuous background in the streaks became more weak than at 290℃.
Upon further annealing, number of dots in the streaks decreased, finally disappeared after final annealing.

There are a number of relations between various types of boundaries [2].
For a large number of random grain boundaries which can be thought of as uniformly distributed points in the five-dimensional space, the fractions are related to total volumes of spaces bounded by specified limits surrounding points corresponding to, respectively, ideal tilt, twist, symmetric and improperly quasi-symmetric boundaries.
Maximum relative uncertainties of these integrals are estimated as N -1/2, where N is the number of sampling boundaries falling in the volumes.
Symmetric boundaries, which have the most particular geometry occur extremely rarely, but the number of improperly quasi-symmetric boundaries is of the same order as the number of twist boundaries.
It has been confirmed that the amount of geometrically characteristic boundaries among random grain boundaries decreases with the decrease of the number of point group symmetry operations.

Table 1 Chemical composition of the steel Chemical composition [mass.%] C Mn P S Si Al Nb V N 0.082 1.54 0.01 0.006 0.36 0.033 0.055 0.078 0.005 Journal Title and Volume Number (to be inserted by the publisher) 3 Results and discussion Three different possibilities for grain growth were explored in order to explain the preferential growth of the large grains: (i) transformation induced recrystallization; (ii) selective growth of specific orientations and (iii) growth advantage based on the fact that first nuclei grow first.
The grains larger than 10 µm and smaller than 3 µm were selected as representatives for the large and the small grains (cf.
The local misorientation between the large grains (grain 1) and the neighboring grains (2, 3 etc.) is measured between the marked points.
Journal Title and Volume Number (to be inserted by the publisher) 5 misorientation data between large and small ferrite grains.
The black line in Fig. 8 shows the grain size distribution of the ferritic grains at temperatures close to Ar3 and it is easy to be seen that the area fraction of the large grains is relatively low in comparison to the one corresponding to the small grains.

The cyclic hysteresis loops of UFG Cu shows the tension and compression peak stresses decreased gradually with number of cycles.
The low cycle fatigue behavior was found to be worse than coarse grained material while the high cycle fatigue behavior was reported to show remarkable improvement over coarse grained sample.
The grain refinement is apparent when compared to ~50 μm of the initial grain size prior to ECAP.
The tension and compression peak stresses decreased gradually with number of cycles.
After the first cycle, tension and compression peak stresses were shown to decrease gradually with number of cycles.