Figure 1 Graphic of the structure of BCC ferrite with a vacancy. The vacancy is
located in the row of atoms which is highlighted green.
The materials being simulated in this assignment
are BCC iron, or ferrite, and FCC iron, or austenite. Ferrite is relatively
soft and ductile and is magnetic at room temperature. This BCC structure
has a maximum solid solubility of approximately 0.022 percent carbon. Austenite
is nonmagnetic at high temperatures and its single-phase FCC structure
is ductile at elevated temperatures. Although austenite is not stable below
727C. The FCC structure of iron, since it is more open than its BCC form,
has a higher solid solubility of about 2.11 percent carbon. Therefore,
one would think that the energy to create a vacancy would be higher in
the ferrite structure.
Vacancy Formation in Ferrite
Figure 1 Graphic of the structure of BCC ferrite with
a vacancy. The vacancy is
located in the row of atoms which is highlighted green.
The energy needed to form the vacancy shown in Figure
1 is 5.99 eV. The minimum energy of the block is 541.85 eV. Finally, the
maximum atomic displacement due to relaxation is 0.08377 angstroms.
Vacancy Formation in Austenite
Figure 2 A section of the simulated block of austenite
with a vacancy. The vacancy is
located within the area highlighted in red.
The energy needed to form the vacancy shown
in Figure 1 is 5.86 eV. The minimum energy of the block is 1068.31 eV.
Finally, the maximum atomic displacement due to relaxation is 0.03809 angstroms.
Planar Defect in Austenite
Figure 3 A graphic of the free surface of atoms in the {1,2,0}
plane (highlighted in
orange), in simulated austenite, for which the surface free energies
will be calculated.
The specific free energy of the highlighted plan
in Figure 3 is 3.37 J/m^2. The minimum energy of the block is 818.01 eV.
Finally, the maximum atomic distortion due to relaxation is 0.17851 angstroms.
Works Consulted
Callister, William D., Jr. Materials Science and Engineering: an introduction. 3rd ed. John Wiley & Sons: New York, 1994.
Kalpakjian, Serope Manufacturing Processes for Engineering Materials. 3rd ed. Addison Wesley Longman, Inc.: Menlo Park, CA, 1997.