Search results

Introduction P460N alloy steel comes from the fine grain normalized steels family [1].
Therefore, fine grain steels still remain so fine.
Therefore, it is suitable to be used in welding fine grain steels.
Grain size Groove angles(α) Test regions No.
Table 12 .Macro hardness test based on test regions’ number Groove angles(α) Test regions No.

Grain nucleation in industrial alloys has a heterogeneous nature.
The number of active substrates in the domain V of the melt with an undercooling ΔT below the liquidus may be calculated on the basis of the cumulative distribution function F(ΔT): , (1) where: Nmax is the maximum specific number of substrates for nucleation.
The next way of substrate placement and the undercooling of nucleation selection is proposed in [12] based on the mean number of active substrates in one cell of CA.
The specific shape and volume of this polyhedron, as well as the number of faces and edges depend on the positions of the nearest neighbouring nuclei.
Grain number [m-3]: 1) n = 1015; 2) n = 5·1014.

The grains of base metal (BM) are elongated and composed of a great quantity of low-angle grain boundaries.
Under thermal cycle, the grains here recrystallized dynamically, caused the increase of grain boundary density.
The red arrow in the figure indicated the needle-shaped precipitates, and the red numbers indicated the energy spectrum acquisition positions.
Firstly, the grain size was considered.
The reduction of grain size from 7.2 to 4.5μm generated 22% grain size strengthening, and to 5.8 um in the TMAZ, the grain size strengthening decreased to 12%.

At high peak temperatures, the intense grain growth took place.
An adequate cold reduction is necessary to increase the dislocation density and the number of favorable recrystallization nucleation sites for the gamma-fiber.
Grain size and hardness of annealed specimens.
According to the literature [11–13], the high HR leads to more effective nucleation during the start of recrystallization, resulting in higher number of grain nuclei and thereby a refined GS.
However, at high heating temperatures coarse grain sizes can be obtained as result of grain growth

Particles from 5 to 1 μm in size were found both within grain bodies and along grain boundaries.
Mg2Ca particles up to 1 μm in size are also found in grain bodies, while their size at grain boundaries constituted 4 μm.
Some grains contained high-density dislocations (Fig. 2, c), while large grains were mainly free from dislocations.
Grains have distinct boundaries typical of recrystallized grains (Figure 4b, c, d).
A non-uniform contrast in HPT-processed samples subjected to further annealing at 150 оC implies the presence of a large number of dislocations pointing to still high internal stress in the structure (Figure 5а).

Though the number is quite limited, the recrystallization also occurred inside the grain far from the grain boundary.
[m4s/J]　 (7) Here, is the amount of an alloying element which segregates to the grain boundary, α is the ratio of the segregation formulated by Eq. 8 (8) Here, δ is the thickness of the grain boundary, is the number of atoms in a unit volume, is the grain boundary segregation energy, is the Boltzmann coefficient and D is the grain boundary diffusion coefficient.
A constant n0 is the number of subgrains which start growing abnormally per a unit time.
　 (13) Here, N2 is the number of grains growing toward the center of the grain and is used as an adjusting parameter to fit the experimental result.
N3 is the number of the growing grains and is used as an adjusting parameter.

The grain sizes were calculated with Scherrer formula.
In our previous research paper[1], the grain sizes are calculated with Scherrer formula and 240 nm of averages grain size of Zn milled for 3 h is obtained.
A broad grain size distribution (5-500nm) with a large number of 5-10 nm grains is observed.
Fig.2 shows the normalized yield strength and % elongation data for ultrafine grain materials (grain size of 100 -500nm)[6].
Fig.4 represents the typical ductile fracture which includes a number of dimples, the central interior region of the surface which has an irregular and fibrous appearance.

Three grains, Grain 3, Grain 4 and Grain 5, were only in contact.
At the grain boundary between Grain 3 and Grain 4, strain distribution continued smoothly.
In contrast, discontinuous strain distribution was found at the grain boundary between the Grain 4 and Grain 5.
Mean strains in Grain 1 and Grain 2 were almost similar.
Acknowledgements The SR experiment was performed with the approval of JASRI through proposal numbers 2005B0019 and 2007B1213.

Both coarse and fine grained CM247LC showed similar cyclic stress response, however, the fine grained CM247LC specimen exhibited relatively uniform and superior fatigue properties to the coarse grained one.
Experimental procedure Coarse grained (CG) and fine grained (FG) bars were prepared by vacuum investment casting of CM247LC.
Number of cycles corresponds to 80% drop in maximum tensile stress of the alloy was defined as fatigue life.
Relatively large amount of microporosity in FG was attributed to restriction of capillary feeding in mushy zone due to increased amount of grain boundary area and number of grains.
Number of cycles to failure as a function of total strain range.

dislocation glide, diffusional mass transfer, grain boundary sliding and motion of grains as a whole.
Thus, investigation of the regular features and physical mechanisms which are involved in a number of grain boundary diffusion-controlled processes of structural evolution and plastic deformation in polycrystalline metals and alloys including NS ones, is of great interest to both a researcher and an engineer.
A number of theoretical investigations of GBs have been performed for FCC and BCC metals.
The structural and phase states that forms in the material treated by severe plastic deformation has a number of advantageous features, which is liable to enhance the performance of investigated steel.
Zhu: in Ultrafine Grained Materials III.