Precipitation Morphology

As the spherical particle is the default morphology, for precipitations within the grain, three non-spherical shapes are considered: cuboid, plate and needle.

Growth

Homogeneous Nucleation

Precipitation Calculator: Precipitate Phase Settings

Cuboid

Figure 1: Cuboids have six faces, which form a convex polyhedron.

The cuboid shape is described by a supersphere

with p=2 being spherical shape. The larger the p, the more cubic the shape. Sometimes it is useful to define the cubical character as

Which gives a spherical shape when , and a cubic shape when .

Plate

Figure 2: Oblate spheroids have rotational symmetry around an axis from pole to pole.

The plate is described as oblate spheroid

with aspect ratio

Needle

Figure 3: A prolate spheroid is a surface of revolution obtained by rotating an ellipse about its major axis.

The needle shape is described as prolate spheroid

with aspect ratio

Precipitations at a Grain Boundary, Edge or Corner

For precipitations at a grain boundary, grain edge, or grain corner, non-spherical particles are considered based on wetting angle.

Heterogeneous Nucleation

Precipitation Calculator: Matrix Phase Settings