Search results

The coarse grained tungsten carbides are mainly used in mining or drilling applications.
A reduction of the WC grain size, on the other hand, increases the hardness and improves other mechanical properties [7,8].
In the applied research of ultrafine cemented carbide, Liang Ping[9] and Yu Jiedong [10]et al. showed that ultrafine cemented carbide tool life improved several times over the conventional coarse grain cemented carbide; Pan Yongzhi [11], Kuai Jicai [12] and Zhang Hui [13] et al. indicated that grain refinement significantly reduce the friction coefficient of the ultrafine grain cemented carbide by the friction and wear testing.
Cutting Tool Material Tool materials that were selected for cutting test is YG6 and YG8 with the grain size 2 to 3μm as well as YG6U and YG8U with the grain size 0.2 to 0.3μm.
Thirdly, ultrafine WC/Co cemented carbide tools have a finer grain size, bigger grain surface area, larger volume fractions of grain boundaries twists and uniform distribution of binder phase Co, greater impeding the generation, motion and propagation of micro-cracks, so that the possibility of WC grain being removed reduce, the chipping of cutting edge is more difficult .

Besides, the resolution process in the proximities of grain boundaries is considered in a different way, and the grain growth mechanism from a specific temperature threshold is implemented into the code.
Grain boundary gas and resolution approach The fission gas reaching the grain boundary is divided in two fractions, one of them is accumulated in the grain boundary and the other is resolved.
Grain growth implementation The grain growth mechanism has been considered in the FRAPCON-3 code, to investigate its effect on FGR results.
The expression for the limiting grain size, at which grain growth ceases, includes Ainscough and other author's data for temperatures up to 2713 K, excluding values with limiting grain size greater than 250 µm: )m()T/7620exp(101.1a 3 max µ −⋅=
The cases with high deviations in the positive range are those -120-100 -80 -60 -40 -20 0 20 40 60 80 100 120 0 2 4 6 8 10 12 14 16 Relative Error (%) Number of cases -40 0 40 80 120 160 200 240 280 0 2 4 6 8 10 12 14 16 Relative Error (%) Number of cases -60-50-40-30-20-10 0 10 20 30 40 50 60 70 80 90100 0 2 4 6 8 10 12 14 16 Number of cases Relative Error (%) -60 -40 -20 0 20 40 60 80 100 120 140 160 180 200 0 2 4 6 8 10 12 14 16 Relative Error (%) Number of caseswith final burnups near 50 GWd/tU and very low release (1-2%).

Introduction Nanocrystalline materials consisting of nanometer-sized crystalline contain a large number of interfaces such as grain boundaries and triple junctions, and thus, a large volume fraction of atoms are associated with the intercrystalline region [1].
Results and Discussion The occurrence of grain growth in the specimen resulted in the change of crystallographic textures as follows.
The texture evolution that takes place during annealing can be attributed to relatively faster growth of the <111>//ND grains than the <100>//ND and other oriented grains.
TEM and OIM analysis were used to obtain the grain size for the as-deposited and annealed specimens.
When the mechanical properties were measured by means of the nanoindentation test, the annealed specimen exhibited a lower hardness due to grain growth and a higher elastic modulus due to the high density of the <111>//ND grains in comparison of the as-deposited specimen.

Although observed in various metals of diverse crystal structures, twinning is most prominent in hcp metals, which often have an insufficient number of slip systems to accommodate externally imposed strains [1].
While the twinned grains were refined due to sub-division by the twins, the untwinned grains, which had undergone only slip, had a largerthan-average grain size.
Hence, due to the high stored energy and the large number of high-angle boundaries, heavily twinned regions and particularly the regions of twin boundaries impinging to the prior grain boundaries become favorable nucleation sites for recrystallization.
Texture evolution during grain growth thus appears to arise from the size advantage of the recrystallized grains.
Vol. 50 (2002), p. 1245 12345678910 0 10 20 30 40 Overall specimen (a) Ave. grain size 3.9 µm Frequency [%] Grain size [µm] 12345678910 Grains with CRTC (b) Ave. grain size 3.1 µm Grain size [µm] 12345678910 Grains with RXTC I (c) Ave. grain size 4.2 µm Grain size [µm] 12345678910 Grains with RXTC II (d) Ave. grain size 4.3 µm Grain size [µm]

The more diamond grains are produced, the thinner battens of metal carbides in catalyst disc are formed.
For the different content of boron-carbon added to catalysts, the numbers of diamond grains synthesized are different.
The number of diamond grains in 1 # and 3 # samples are more than that in 2 # and 4 # samples.
The battens around the diamond grains are thinner, as shown in Figure 4a, b.
Synthetic diamond grains are embedded in the catalyst disc.

The effect of the loading conditions on the number of cycles to crack initiation is evidenced using a ∆εt-Ni plot.
The majority of the cracks are smaller the average grain size.
In "small SCV slip systems", the effective grain size is much smaller than the actual grain size.
Since the number of PSB remained exactly the same in all the simulated cases, this means that slip irreversibility increase takes place at the scale of individual PSBs.
CONCLUSIONS The number of cycle to initiation of large cracks (50-150µm) in thermal fatigue is 4-5 times faster than in conventional fatigue, for a fixed ∆εt,eq.

By now a large number of studies were carried out on hot deformation behavior of 7075 aluminum alloy [3-6].
After heat treatment the distribution of precipitated phases changed markedly and their number reduced significantly.
Due to low aging temperature there existed a large number of dispersed small h¢ phase.
A small amount of precipitated equilibrium phase h on grain boundary should lead to a lower strength of alloy, but due to large number of h¢ phase and its significant strengthening effect, the strength reduction caused by precipitated h equilibrium phase was offset.
The reasons for fine grains are as follows: First, during recrystallization process a high nucleation rate and low grain growth rate could both lead to grain refinement.

After this grain growth occurs resulting in large grains that meet up at the centre line.
(ii) Nucleation and growth of few grains ahead of the first set of recrystallised grains which grow into the grains with low deformation.
The two above events are illustrated in Figure 2 where grain area of selected grains 1-7’ undergoing growth is plotted against time.
Plot of grain area with time of selected grains in the compressed and tensile regions.
All the initial nuclei labelled 1-4, in Figure 3a were highly deformed and had a number of zero solutions, the arrowed location 4 in Figure 3a had no solution where a near (111) <110> oriented grain labelled as 4’ in Figure 3d nucleated and grew.

Reduction by carbon is carried out on the chromite grain surface due to the cations and anions diffusion in the oxide lattice towards the grain surface.
Reduction by carbon is carried out on the chromite grain surface due to the cation and anion diffusion in the oxide lattice towards the grain surface.
A characteristic feature of this model is the formation of reduced metal particles on the surface of chromite grains in veinlets of host rock or along grain cracks.
The rate of metal reduction, the number and size of the metal particles should be the highest in the surface layers of the ore piece.
Chemical composition of reduced metal in the ore “Voltschegorskaya” Sampling point number Element content, % wt.

Measurements of the size of the grains were made in these areas by seeking.
Installed that the number of SiC particles in the FSW AL25 + 18% SiC composite is more than twice compared to the base composite, though basically same particle volume fractions were observed in both conditions.
Comparative fracographic analysis of welded compounds performed by STP after tests showed that the kinks are caused by a fine-grained structure and a more plastic intra-grain nature of destruction (Fig. 6).
The size of the grain in the mixing zone is a value that is more dependent on the material (the presence of hardening particulate matter of aluminum oxide) and the cooling speed, as both temperature and deformation, which affect the size of the grain, increase with the intensification of the regime.
In addition, as the particle size increases, they increase the density of structure defects, the number of doubles and packaging defects.