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Optimization of Process Parameters for Unidirectional Solidification of Magnesium Alloy Ming Chen1,a Xiao-Dong Hu1,b Hong-yang Zhao1,c Dong-Ying Ju1,d University of Science and Technology Liaoning, Anshan, China 114051, 1a:cchen552@163.com,1,b:hulinas@sohu.com,1,c:zhy@ustl.edu.cn,1,d: dyju@sit.ac.jp Corresponding author: Dong-Ying Ju, E-mail: dyju@sit.ac.jp, Phone:86-412-5928052, Fax : 86-412-5929554 Keywords: unidirectional solidification, finite element method, phase field, columnar grain Abstract: The unidirectional solidification process of magnesium alloy needs to establish a specific temperature gradient in casting mold, the direction of crystal growth and heat flow are in the opposite direction in the unidirectional solidification.
The process can better control the grain orientation, and eliminate the horizontal grain boundary to obtain excellent performance of magnesium alloy.
(5) (6) The parametermeans the strength of anisotropy and is a mode number of anisotropy, for the magnesium alloy we assign the value of 6 to.
For the constant value of , which is according to the macro analysis result when cooling intensity is ~5000W/m2k and pulling speed is 0.1mm/s, we can see the developed columnar grain structure.
For the constant value of , it can be seen that the columnar grain structure is more developed, through the comparison of different value of , it can be known that the higher cooling intensity is, the more developed the columnar grain structure is, but it is hard to make the value less than 1.5 in the actual process, that needs very large cooling intensity.

The SEM images indicated that in as-cast alloys, the Al2Ca intermetallic compound was located at grain boundaries with a lamellar structure, and the Al2Sm intermetallic compound was homogeneously distributed in the α-Mg matrix or near the grain boundaries with a polygonal structure, and the Al11La3 intermetallic compound was located at grain boundaries with a needlelike structure.
Moreover, the Sm addition also declined the number of the β-Mg17Al12 phase compared to that in AZ91 alloy in Fig. 3(a).
It could be found that there is the largest number of precipitated phases in AZ91-1.5Ca-0.5Sm-0.3La alloy , and all the above intermetallic compounds are generated (see Fig. 1), which precipitated in the α-Mg matrix or along the grain boundaries and will obviously restrict the movement of the adjacent grain boundaries.
However, the segregation phenomenon of Al2Sm appeared near the grain boundary.
Greer, Grain refinement of Al alloys: Mechanisms determining as-cast grain size in directional solidification, Acta.

Additionally to the global stress determination, we propose a local grain by grain stress study.
Micro-stresses in electrolyte grains.
Measurements have been performed in ten grains of each sample.
Unfortunately, the low number of measurements does not allow statistical analysis and highlighting a systematical relationship between heterogeneity and grain orientation could not be achieved.
Further investigations with measurements on a large number of grains would allow a statistical analysis between stress and grain orientation.

In present model, deformation in macroscale is transferred to meso-scale, where a representative element contains several, score or hundreds grains, and then is applied in micro-scale to each grain.
Deformation in macroscale is transferred to meso-scale, where representative element contains several, score or hundreds grains, and then is applied in micro-scale to each grain.
The microstructural part calculates the grain refinement during the cold deformation.
Each cell represents small volume that contains many dislocations and number of dislocations or their density is used as parameter of the cell.
For the other slip direction 1D CA is decomposed on such number of 1D CA how many parts were cut by LABs.

We have covered three different grain sizes of particles.
The possible solution of these problems can be the plating of the SiC grains.
A number of common reducing agents have been suggested for use in electroless copper baths, like formaldehyde, sugars, hypophosphyte.
The copper deposit is light, and there is on the dark grey grains.
If the coating time increases, the numbers of the particles and the plating rate increase, as well.

Introduction At present, the earth experiences a large number of earthquakes every year, causing huge damage to human life and property.
The grain size of ferrite was coarse, with some hybrid crystal phenomena, and the average grain size was only 5.0.
This was due to the relatively low reddening temperature after the roll, which increases the cooling rate of the sample, and the fact that the grains were too late to grow, and therefore more fine grains were obtained.
The internal structure of rolled 1 # steel contains a large number of mixed crystals, and normalization at different temperatures will still lower the overall mechanical properties of the material.
The grain sizes were 8.0-8.5 grades, respectively.

The top surface comprises equiaxed grains, and columnar grains are observed in the cross-section.
As the grains grew larger, the grain boundaries became more obvious, as shown in Figs. 4 (a) and 4(b).
The number of these structures increased with time, and their growth was intertwined and overlapping.
Additionally, the number of particles in each rod-like structure also depended on the reaction time; it was diffusely molded between the particles, and joined together.
The morphology of the cross-section comprises columnar grains and the top surface is composed of grains that are almost equiaxed grains.

Line intercept method was used in order to perform grain size analysis since this method is recommended particularly for grains that are not equiaxed.
The number of grains intercepted by the line was calculated, NL.
If grains are assumed to have an ideal shape, and the same grain size, it is possible to derive an expression of d = 1.5/ NLgiving a true value for grain diameter, d, and (the diameter of an inscribed circle) from linear intercept measurements made in a random planner section.
Figure 1: Linear intercept method for grain size measurement where X marks indicated intersection between grains and line.
Grain size analysis Based on the micrograph obtained from the optical microscope, the grain sizes are measured to know the actual size of the grains formed so that the effect of aging time on grain size will be known.

Very rarely has toughness been measured with a number of alternative quench paths sufficient to fit predictive equations.
For Alloy 7085 we did fractography on a limited number of the used R-curve specimens of Alloy 7085.
In a range of high hold temperature, precipitation is found only on grain boundaries.
At medium and low hold temperatures, precipitation on subgrain boundaries exceeds precipitation on grain boundaries.
This pattern was first recognized from early datasets with a limited number quench paths [14].

The smaller grain size of the composite microstructure the higher hardness can be achieved.
Conventional vacuum sintering could be reliable and simple technology to produce cermets with average grain size >1 µm, but it becomes quite challenging to obtain submicron grains [4].
To minimize the number of variables hardmetals with same binder volume (24%) and mass (15%) fraction and similar average grain size (<1 µm) will be studied.
Each grain was separated manually by a thin line to avoid errors in the data analysis.
Results and discussion The indentation surface fatigue tests were repeated at least three times for each number of indentation loading cycles, respectively 1000, 10 000 and 100 000.