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Takao et al. [7] found two features of slip band in a grain of carbon steel: it was nearly equal to the grain size at early stage of fatigue process; and its length did not change during the fatigue process.
N and Ni mean number of cycles and fatigue crack initiation cycles, respectively.
Therefore the author proposed a new analysis method to define aspect ratio of crack at notch root using average ferrite grain size df.
Number of cycles to the test was 9.8×105.
While the minimum surface crack length is independent from depth, the maximum surface crack length increase as increase in the polished depth as well as the number of surface cracks.

Table1 Chemical composition of sijiaying sinter Numbers TFe/% FeO/% SiO2/% CaO/% MgO/% R S50 54.31 9.36 6.33 11.98 2.50 1.89 S60 53.84 9.14 6.56 12.32 2.50 1.88 S70 53.50 8.62 6.69 12.77 2.50 1.91 S80 53.18 8.79 6.91 13.06 2.50 1.89 S90 52.75 8.42 7.14 13.50 2.49 1.89 S100 52.29 8.36 7.20 13.78 2.47 1.91 Composition of different rational Sijiaying fine iron powder Composition and volume percentage of Sijiaying sinter is shown in table 2.
The distribution of calcium ferrite is even everywhere, and grain sizes further decrease.
Plate columnar calcium ferrite increase, and grain size is bulky.
Calcium ferrite are mainly board columnar whose grain size increases when the proportion of Sijiaying iron ore is 100%.
The grain size is gradually smaller than before, and correspondingly, The strength of sinter increase. when the ratio of Sijiaying fine iron powder is 100%, the content of calcium ferrite decrease slightly, The shape mostly are board columnar, the particle size increase, the strength of sinter decreased slightly.

At the tip and water chestnut of the silicon phase arouse stress concentration, crack formation along the grain boundary and flake or needle form silicon body, the mechanical properties of the alloy decreases.
The size of the silicon phase was non-uniform and the number of α-Al dendrites became less.
The number of α-Al dendrites increased and became short rods.
When the amount of Sr was so small, the undercooling of eutectic will be smaller and the boundary of twin grain will be larger.
Grain refinement for near-hypoeutectic Al-Si alloys [J].

Induction-heated steel bars have a high strength due to hard surface layer and the refined prior austenite grain size [6-7].
Fig. 4(c) is the etched surface consisted of fine prior austenite grains and some martensite packets.
Figure 6 shows the relation between number of reciprocation cycles and wear depth.
The wear depth of SUS304 steels (▲, ▼) were increased with the number of reciprocation cycles.
Fig. 6 Relation between wear depths and number of reciprocation cycles.

The results shown that the compressive residual stress of QT800 by LSP is over 400MPa, and its fatigue life is increased 20% than that in primitive state; the fatigue resource or the sample by LSP is produced near the graphite, compressive residual stress and refined grain effectively delays cracks initiation of the fatigue source, the expansion speed of fatigue cracks is decreased, which increases fatigue life of QT800.
From Fig.3 (b), it could be seen that grain refinement significantly increased by LSP, and dislocation tangles were appeared that improved the material yield strength, which impeded dislocation movement and delayed the formation of surface fatigue cracks.
The fatigue of QT800 after laser shock occurred on the surface of graphite near the source, shown Fig.6 (a), a large number of cleavage steps and dimples happened, that was due to the sample surface after LSP produced a compressive residual stress, which made the crack source difficult to form a strengthening layer, the crack generation hampered under the surface residual stress.
The fracture area fast occurred in the applied load, shown in Fig.6 (c), it showed that laser shock wave produced by the compressive residual stress and grain refinement on the fatigue crack initiation and propagation had obviously limited role, which helped to improve the fatigue life of the crankshaft.
(a) The fatigue resource (b) The extension area of fatigue crack (c) The area of final rupture Fig.6 The forming of fatigue rupture of QT800 in primitive state (a) The fatigue resource (b) The extension area of fatigue crack (c) The area of final rupture Fig.7 The forming of fatigue rupture of QT800 by LSP Conclusions (1) Grain refinement, residual stress and the diameter of graphite balls are formed by LSP on QT800 surface, which is helped to delay fatigue cracks and its expansion

After laser surface melting the grain structure is refined.
While the average grain size in the untreated base is around 50 µm, the average grain size in the laser treated zone is around 20 µm.
Precipitates occurred also inside the grains.
ZE41 is a complex alloy with a number of eutectic microconstituents.
The laser treated zone has an average grain size of 20 µm, while the base alloy has the average grain size of 50 µm.

Therefore there were probably even larger grains present in the sampling volume for these measurements.
It has been found that in the fusion zone grain sizes can be 1 mm or more.
Wimpory et al [8] show that in general the use of larger sampling volumes mitigates the data scatter associated with grain size effects.
This improves the homogeneity of the distribution of diffracting grains across the sampling volume, and therefore reduces the data scatter associated with grain size effects. 10° Fig. 5 Rocking the TG1 specimen by ±10° about the measurement position The effect is well known.
In 2003 distance between two measurement locations was only 1 to 2 mm, i.e. a large number of individual measurements has been taken from underneath the weld bead.

It has also been noticed that the number of independent slip system of the basal slip is two, which is insufficient to carry out a compatible deformation in randomly oriented polycrystal.
The grain sizes of the as-received and as-annealed specimens were measured by the line intercept method.
Result and Discussion Flow curves affected by the grain-refining treatment are shown in Fig. 1.
The yield stress of the bar specimen is increased after the grain-refining treatment.
The grain size effect i.e. the rolling angle effect is analyzed and no special function has been found, which might be attributed to the narrow range of the grain size.

The average grain size was 10µm measured by the lineal intercept method as illustrated in ASTM E 112-96.
The newly formed interconnected carbides made the definition of the grain size obvious (average grain size: ~40µm * 65µm).
Although there was a significant growth in grains, the average grain size was relatively small owing to the carbide pinning effect.
The difference in the results obtained by these two techniques may have been due to the resolution of the X-ray microtomography and the number of 2D images considered.
A grain growth was also observed during heating.

Columnar martensites and a number of film austenites retained along the lath of martensite comprised primary microstructure. δ-ferrite was formed and the volume fraction of δ-ferrite increased as the chromium equivalent (Creq) of steel composition increased.
The morphology of δ-ferrite changed and columnar martensite grains were broken in sub-zone I and II of WBHAZ.
Table 1 Parameters of the submerged arc welding Serial number Items Parameters 1 Wire T91 2 Welding flux CHF605 3 Preheat temperature [ºC] 200 4 Interheat temperature [ºC] 200~250 5 Wire diameter [mm] 3.2 6 Arc voltage [V] 26 7 Current [A] 450 8 Welding speed [cm/min] 55.88 Fig. 1 Cross-section of 9Cr-1Mo deposited metal showing the location for microstructure observation.
Conclusions (1) The morphology of δ-ferrite transformed and columnar martensite grains were broken when the primary microstructure was subjected to the thermal cycle at the temperature of melting point