Search results

The original structure is equiaxed, and the average grain size of α phase is 9.3μm.
Due to the short forming time and low forming temperature, the average grain size changed little and the average grain size on the workpiece was 11.6μm after forming.
Moreover, grains grew in the hoop direction. 4.
Acknowledgement The authors would like to thank for the supports from National Natural Science Foundation of China (Project numbers: 51075100 and 51105203) References [1] F.

The number of motor-pumped wells in Wuwei city were 3233 in 1989, which rapidly increased up to 16900 in 2000, thus the motor-pumped wells became to popular agricultural irrigation method.
Put strategic management of virtual water into effort gradually Hexi Corridor, including Shiyang River Basin, had been a commodity grain base for the lack of grain.
Under the condition that the grain have been abundant relatively with pen international and domestic market, the development of traditional inefficient agriculture will restrict the water flow into the other non-agricultural industry with relatively high water use efficiency.
So the concept of commodity grain base should be abandoned and the strategic management of virtual water, namely one country lack of water import crops from water-rich countries as the water contained in crops, could be implemented gradually, thus the scarce water resources will produce most ecological, social and economic benefit.

Zhao [7] has mentioned in the previous literature that this phenomenon is due to the production and multiplication of large numbers of mobile dislocation from grain boundary at the early deformation stage, causing the rapid increase of deformation resistance; subsequently, the dislocation migrates from the grain boundary into the grain, leading to an obvious decrease in the flow stress.
It can be seen from Fig. 4 that the grains are severely flattened and elongated, and the micrograph has obvious direction.

Due to the extremely high melting temperature, MC carbides can precipitate from the melt at first as fine solid particles that additionally increases the number of nuclei in the melt [6] resulting finally in the solidified structure refinement.
As a consequence, being not dissolved during austenitisation, these carbides are capable to protect austenite against its grain growing even at a high temperature and therefore the final microstructure of a martensitic matrix is more refined that results in enhanced mechanical properties.
In these steels the MC carbides primarily precipitated in the interdendritic regions in the form of thin rods that formed a semi-continuous carbide network along the matrix grain boundaries.
The amount of coarse angular MC carbides inside grains in these steels was also larger, and this effect was more pronounced in steel 3.
The broken carbide networks over the matrix grains were still present after annealing, as shown for steel 1 and 6 (Figs. 2a and 2c).

The impacts cause plastic deformation in the surface layer of the treated sample, leading to grain refinement and large grain boundary misorientation, dislocation blocks and microbands [3].
Meanwhile, the inner surfaces of the grinding vial are also continuously impacted by a number of flying balls carrying some powder, resulting in the deposition of the treated powder on the inner surfaces.
The broad, but overlapping peaks suggest the formation of small nanograins in the coating layer, however, quantitative grain-size analysis is not possible.
The Ti and Zr peaks are broadened by grain refinement and lattice strain and they may conceal a very small amorphous fraction.

Internal friction can be due also to the viscous motion of domain walls in the lattice [5]: in this case, the relaxation strength depends on the number of walls per unit length which increases when the temperature T approaches the Curie temperature TC.
Table 1: Activation parameters for the R peaks Activation parameters Peak R1 Peak R2 H (eV) 1.9±0.1 1.1±0.1 τ0 (s) 10-18 10-13 We have studied the influence of the grain size on the internal friction spectra.
When the grain size increases, the R2 peak height decreases and the R1 peak height increases slightly.
We have a homogeneous microstructure consisting of polyhedral grain of uniform size (about 25 µm).
Conclusion Ceramics with high hardness and high rigidity can exhibit high damping not only at high temperature (due to grain boundary relaxation) but also at low temperature.

A variety of particulate- reinforced composite models has also evolved from the above approaches by further considering microstructural features contributive to the matrix flow stress (e.g. residual stresses, solute and precipitation hardening, grains and sub-grains lattice disorder,…).
The second feature enables in turn to drop the assumption of mean number of fibre segments from fibre breakage having always to be a multiple of two whatever the initial fibre length.
This is the case of metal-matrices hardening by internal stresses or solute or grains and sub-grains or precipitates action; or reinforcements weaknesses as introduced by localized flaws; or volume fraction effects (e.g. matrix embrittlement at too high fibre volumes or fibre interaction at too low fibre volumes).

The ADC module applies thermodynamic chemical potential equality equations of paraequilibrium condition, material balance equations for the ferrite/austenite interface advancing in a spherical austeinite grain (earlier for carbon only but now also for nitrogen and boron) and regression formulas optimized from English and German CCT measurements, where the influencing solutes are C, Si, Mn, Cr, Mo and Ni.
In this case, the excess element (particularly hydrogen) can be concentrated in grain boundaries or micro holes (formed by plastic deformation), where it can take a gaseous form.
At low temperatures, the gas pressures can grow very high and cause cracks advancing along the grain boundaries of the expanding micro holes.
The developed function has been validated by a great number of experimental data.
The HOM module simulates: 1) Homogenization of composition profiles (microsegregation), 2) Compound (precipitate) growth or dissolution, 3) Ferrite growth or dissolution, 4) Growth of austenite grains (approximate method for low alloyed steels).

., form segregations at grain boundaries resulting in abrupt changes of mechanical properties [1].
But many steels contain a number of alloying elements, and it is not always easy to say if phosphorus causes brittleness by itself or as a result of interaction with other impurities.
Grabke, Equilibrium segregation of phosphorus at grain boundaries of Fe–P, Fe–C–P, Fe–Cr–P, and Fe–Cr–C–P alloys, Metal Science, 15 (1981) 401-408
Kimura, Effect of carbon on the grain boundary segregation of phosphorus in α-iron, Scripta Metallurgica, 17 (1983) 1325-1328
Hartmaier, Solubility of carbon in α-iron under volumetric strain and close to the Σ5 (310)[001] grain boundary: Comparison of DFT and empirical potential methods, Computational Materials Science, 50 (2011) 1088-1096

Consequently, it is characterized by a high proportion of unhydrated cement grains together with a dense (micro)structure.
Above this value, the mixture contains enough water to ensure the hydration of the cement grains and fill the small capillary pores.
The measurement of the resistance to F&T cycles is based on the testing of mechanical properties (strengths and dynamic modulus of elasticity) of specimens subjected to a specified number of F&T cycles.
These values decreased when high-quality sand grains were substituted with low-strength LWA grains.