Flake graphite iron, compacted graphite iron and spheroidal graphite iron with various tensile strengths were cast. They were selected and grouped according to roughly the same tensile strength, and then the main cutting force in each group was measured and compared. The microstructures of different cast irons were characterized. The relationship between the cutting force and microstructure was established. Results show that the graphite morphology in cast irons determines the strength. In order to obtain the same strength of the cast iron with sharply edged graphite, more or finer pearlite in the matrix is needed. Graphitic cast irons with high pearlite content and smaller pearlite interlamellar spacing have higher hardness. For the cast irons with different graphite morphologies, but almost the same tensile strength, the main cutting force is obviously different, along with the hardness. Harder cast irons have a greater cutting force, but the difference in cutting force is not proportional to hardness.
The fourth order Runge-Kutta method was used to solve the Thomas-Fermi-Dirac (TFD) equation. This method simplifies solving the TFD equation and improves the solution accuracy. The electron density of Cu at the Wigner-Seitz atomic radius was calculated as an example, using the TFD equation. The same method was used to calculate electron densities of other 24 elements at the Wigner-Seitz radius. These results demonstrate a successful application of the Thomas-FermiDirac model in materials research.
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