Search results

Figure.1 Correlation between a marine oxygen isotope δO18 reference curve (numbers signify stages) with Zhuli section, 1-cultivation intervals, 2- loess intervals, 3- paleosol intervals.
Grain-size analysis All the samples show a bimodal grain size distribution (Fig.2a), with higher mode at 79-89μm and lower mode at 10μm and the valley at about 20μm.
(b) Grain-size classes vs. standard deviation of Zhuli section Figure.4.
Records of magnetic susceptibility and grain size in Zhuli section.
(2) All the samples show a bimodal grain size distribution, and grain-size curves indicate that environment-sensitive size fractions of this section are 39.81-44.67μm and 79.43-89.12μm respectively, by analyzing grain-size class vs. standard deviation values method

(2) Where:- average grain size,- dynamic recrystallization volume fraction, - dynamic recrystallization grain size ,- initial grain size.
Grid number is 80000; the mould is arranged as a rigid body, the whole grid division number 10000.
Simulation results analysis Analysis of the temporal and spatial evolution of grain.
A large number of deformation occurs in the middle of the process, and most of the region is in the recrystallization temperature range, so a large number of dynamic recrystallization can occur at a high speed.
It can be seen that, time which happens a large number of dynamic recrystallization is at the beginning of the forging process.

In this reference, SE-Cu 58 (99.95% copper) with fine grains showed a higher flow stress for 25 and 500μm foil than coarse grains.
A number of references considered the effects of nose radius against punch diameter for 0.5mm thick AZ31-O [20] and Al-O [21].
The number of layers of material ARB2c, ARB3c, and ARB4c were 18, 36 and 72 layers, respectively.
The grain size d obtained by EBSD method are shown in Fig. 5 and 6.
Approximately 93% grain refinement has occurred after the first ARB cycle ARB1c, and about 0.6% change in grain size between the first and fourth ARB cycle.

So in commercial point of view there is a need to reduce the strain and number of passes required to produce ultrafine grained structure by ARB processing.
The region shows grains in the size range of ultrafine grain material by definition i.e., grain size range 200nm-800nm.
The grains are fairly equiaxed in shape.
It is proposed that large number of dynamically recrystallised grains form in the material at the end of 2 pass ARB itself and they are more copious in the 3 pass ARB.
(a) (b) (c) (d) Conclusions Al-2.4wt%Cu-0.3wt%Si alloy was conventionally rolled to a rolling strain of 2.46 followed by accumulative roll bonding process to different number of passes.

A grinding wheel comprises of a large number of grains and their size and distribution are random and therefore it makes the grinding process a very complex machining process to be studied.
However in reality, the single-grain cutting process is not easy to be studied using traditional experimental approaches because the grain is too tiny at micro scale.
Further Niklaus et al.[10] conducted a simulation of single grain cutting using the SPH method to investigate influences of grain geometry, grain orientation and grain placement on cutting forces, burr generation and chip removal rates.
Modeling of Single-grain Cutting In the current study, the single-grain cutting model was idealized as a RHA 4043 workpiece (160 μm in length, 100 μm in width and 40 μm in height) and a single cutting grain as shown in Fig. 1.
Fig. 2 The numerical modeling of the single-grain and the geometry of the grain In the numerical simulation, the grain was moved along the positive direction of the z-axis in a defined moving path depicted in Fig. 3.

Grain refinement of Zn-25Al alloy through the addition of Zn-6Ti master alloy Z.Q.
The mechanism for the grain refinement is discussed based on the SEM observation of TiAl3-xZnx particles at the center of α-Al grain in Zn-25Al alloy.
Recently, grain refiners, e.g.
In this paper, we will briefly report the grain refinement of Zn-25wt.
The α-Al grains in the original Zn-25Al alloys (without the addition of grain refiner) solidified from 570℃ present complex dendritic structure which contains a number of primary and secondary arms, which exceeds 300μm and 70μm in length, respectively(Fig.4(a)).

In addition, an inclusion of length scale of grain to simulate the SIMT behavior is very important and the studies which consider the effect of numbers of grains and representative grain morphologies effectively are still developing.
The actual TRIP steel is a polycrystalline material which consist an aggregate of a number of grains and the martensitic content varies from grain to grain.
A set of Voronoi tessellation with the numbers of crystal grains of 6 and 20 is chosen as shown in Fig. 2 (a) and (b).
Here, the total number of variant systems is 24 [14].
Next, Fig. 5 shows the distribution of phase for the case of 20 grains with Pattern 2 in order to investigate the effect of numbers of grain on the SIMT behavior.

It is found that the area fraction and numbers of proeutectoid ferrite grain as well as the lamellar spacing of pearlite in Fe-0.76%C alloy increased considerably with the increase of magnetic field intensity.
The area fractions and grain number of proeutectoid ferrite and the angle between the major axis of proeutectoid ferrite and magnetic field direction were analyzed by an image analyzer.
Moreover, it is also observed that the area fraction and grain number of proeutectoid ferrite increased considerably with the increase of magnetic field intensity.
Based on quantitative analysis of the changes of area fraction (figure 3) and grain number (figure 4) of proeutectoid ferrite, it can be seen that the proeutectoid ferrite area fraction increased from 0.64% to 3.139% and the number of ferrite grains increased more than twice as the intensity of the applied magnetic field was elevated from 0T to 12T.
This is considered as the reason for the increase in the area fraction and the number of proeutectoid ferrite grain in the specimens treated with the magnetic fields.

The corresponding selected area electron diffraction (SAED) pattern in Fig. 1 (a) was taken from an area of 4µm in diameter, diffraction rings are exhibited implying a large number of ultrafine subgrains/grains form in the diffraction area, however, quite discrete diffraction spots exist in the rings suggesting low-angle boundaries (LABs) and relatively coarse subgrains dominate in the structure.
Fig. 2 (c) shows the grain size distribution measured from dark field images, the mean grain size is 77nm, the largest fraction ranges from 60 to 80nm, while no grain size above 180nm is detected.
The 45 steel exhibits a homogeneous and finer grain size with HABs dominating.
By contrast, the pure iron exhibits an inhomogeneous ferrite structure, which consists of a large number of coarse subgrains with primarily LABs containing an excess of extrinsic dislocations.
HRTEM was used to detect the fine particles in the ferritic matrix, and a certain number of cementite particles with sizes around 10 nm or even smaller are resolved inside the ferrite grains.

Two distinctive groups of materials fall into this category: Nanocrystalline (NC) materials with grain sizes up to 100 nm, and ultrafine-grained (UFG) materials with grain sizes ranging from 100 nm - 1 µm [5, 6].
ECAE processing is generally described by the number of extrusions and the so called processing route.
The impurities in the material of commercial purity further stabilize the microstructure by pinning the grain boundaries, resisting grain coarsening and grain boundary rearrangement.
Slight changes that occur upon cyclic deformation include more well-defined grain boundaries and decreased dislocation density in the grain interiors.
It should be also noted that the grain size observed in the TEM is smaller than the grain size obtained from EBSD measurements.