Search results

The ECAP was made at ambient temperature with the channel intersection angle of 90°, the number of passes was 8.
The grain boundary strengthening is given by the Hall-Petch equation [9]:
Results and discussion As it was shown elsewhere [6-8] that the SPD processing described above produces a ultra-fine grained structure with the average grain size of 200..240 nm.
The refinement of the grain structure by the SPD increases the absolute value of the corresponding contribution almost by a factor of 7.5 versus coarse-grained IP alloy.
Rybin, The grain boundaries in metals, Moscow, Mechanical engineering, 1980

It is seen that many abrasive grains penetrated into the soft-material.
In Fig. 6(a), the grain size of the abrasive particle was constant to be #3000.
The stress value is about 2.6 MPa when the grain size is #1500, while it is about 4.2 MPa when the grain size is #3000.
The grooving efficiency is high when the grain size of the abrasive particle is large, because the large grain size possesses the large space, namely chip pocket, between particles.
Thus the large grain quickly becomes small grain under high static normal stress.

is the number of cycles from which becomes positive.
Fig. 5 gives the evolution of the elastic modulus vs the number of cycles for the test 25-225.
Thin twins are observed is some grains (not represented here) and no martensite is detected.
Martensite blocks are also observed near triple grain boundary junctions.
For the sample submitted to a stress amplitude of 300 MPa (Fig.7c), well defined dislocation cells appear in the small grains whereas for large grains, dislocation walls are observed.

The simulation results showed that system and grain average energy were heighten with the decrease of the grain size, while the grain boundary was declined; elastic modulus of nanocrystal is smaller than normal polycrystal, and decreased with the grain size decreasing.
So there are the limited to number of potential function, simulation smaller, time-consuming, simple simulation model and so on.
So it should be further investigated the modeling method in the description crystal material defects, and establish more atomic number of large-scale simulation model.
The atomic number of the simulation commonly is at most only twenty thousand, in order to reduce the time and use high performance computer to set up many of the atomic number of simulation model.
From the aspects of atomic scale to study the mechanical behavior of materials, especially study the crack, dislocation, grain boundaries and their interaction .It is feasible and more fundamental.

The microstructure of the HPDC AlSi9MnVZr alloy consists of two distinct types of primary α-Al grains: finely dispersed grains formed within the die cavity and coarser externally solidified crystals (ESCs).
The rapid cooling inherent to high-pressure die casting restricts grain growth, resulting in small, near-globular α-Al grains.
In contrast, Fig. 4(b–b1) demonstrates that increasing the intensification pressure to 13.7 MPa results in a dramatic reduction in both the number and volume of pores.
This trend is shown in Fig. 5(c), which shows a significantly reduced number of pores at all depths under higher pressure, particularly in regions prone to shrinkage.
Fig. 5 Statistical analysis of (a) total porosity fraction (%) and number of pores; (b) porosity fraction (%) and (c) number of pores at different distances from the surface to center; (d-e) sphericity under varying Intensification pressure.

Unlike that of the base metal (a), SZ (stir zone, d) had a fine, equiaxed grain structure and the grain size was much smaller than that of base metal.
The elongated and recovered grain structure was characterized in TMAZ.
No precipitates were observed at the stir zone due to the resolution in the Journal Title and Volume Number (to be inserted by the publisher) Al matrix.
Very coarsened grains structures were observed overall weld.
Regions of BM, HAZ and TMAZ had a grain structure near 2 time larger grain size relative to those of as welded specimens.

This trend is associated with the number of reversible hydrogen traps (dislocations, subgrain boundaries, etc.) present in the microstructure.
The latter observation may be related to the low amount of residual hydrogen in this condition and a high number of reversible hydrogen traps (Table 2), which precluded formation of critical sized nuclei.
Cracks were developed irrespective of the microstructure across ferrite grains, pearlite colonies or granular bainite.
Analysis of grain orientations showed that grains with the same crack plane exhibit wide orientation spread, e.g. there was no preferential orientation for crack development.
(a) Magnified view of crack arrest at low angle grain boundary in the EFP sample.

In the optimised conditions, IN718 alloy ring preforms were characterised by a microporosity of less than 1.5% and randomly oriented equaxied grains of 20-50 µm.
The secondary break-up mechanisms are controlled by the Weber number [9].
(e) An EBSD orientation map for the marked area on (d), showing the as-sprayed grain structure and the porosity band between deposition layers.
(e) An EBSD orientation map for the marked area on (d), showing the typical as-sprayed equaxied grain structures and the average microporosity of 1.5%.
No macrolevel defects were found in the central area of the ring cross section as shown in Fig. 6(d) and the as-sprayed grain structures were characterised by randomly oriented equaxied grains with an average size of 42 µm.

Since reform and opening, China's grain production has made great achievements.
The intensive and overuse of chemical fertilizers in China has contributed to a number of domestic and global environmental problems.
The grain crops include wheat, rice, maize (corn), and soybean.
The results indicate that the fertilizer use efficiency effect plays the dominant role in increasing fertilizer use intensity of grain crops.
This reflects that the advancement of fertilizer use efficiency is effective for reducing fertilizer use intensity in the grain crops.

Reactive alloying approaches have recently been introduced to improve PBF-LB microstructures by modifying the solidification process and grain morphology.
Besides the dendritic grain structure, areas with fine, equiaxed grains are also present, highlighting grain refinement likely caused by ceramic reinforcement particles.
Its high melting point and thermal conductivity increase local cooling, hindering grain growth and strengthening the alloy through grain refinement, dislocation pinning, and load transfer Fig.1.
Both orientations exhibit a typical fatigue response, characterized by a decrease in stress amplitude as the number of cycles increases.
Lee, Reactive alloying in laser powder bed fusion: solidification control and grain refinement, Addit.