Computational Materials Engineering

6

Modeling Precipitation as a Sharp-Interface Phase Transformation

Ernst Kozeschnik

During phase transformations, a new phase grows at the expense of an existing phase. The new phase and the existing phase, or parent phase, are distinguished by either a different state of matter (e.g., liquid water droplets in a saturated H₂O vapor, solid crystals in a liquid melt), different crystal structure (e.g., solid bcc iron (ferrite) in solid fcc iron (austenite) in steels) and/or chemical composition (e.g., coherent L1₂-ordered fcc Ni₃Al precipitates in an fcc Ni-Al alloy).

In this chapter, it is assumed that the growing and the shrinking phases are clearly and unambiguously separated by a phase boundary, the interface. The thickness of this interface ...