Solid-melt gamma surfaces

Introduction

Gamma surfaces are usually considered as an important concept to understand stacking faults, dislocation formation and plastic deformations. A crystal is cut into two halves, which are shifted against each other. Due to the mismatch of the lattice planes the energy therefore depends on the translation of the crystals. Often, not only for perfectly aligned crystals but also for certain lateral shifts local minima of the energy can be reached - corresponding to a stacking fault.

Such gamma surfaces can also be observed if the crystal is not just cut and displaced, but also if it is molten along the cut. This way, a melt layer is formed between the two half crystals, and their mutual interaction depends on the thickness of the melt layer.

Fig. 1: Gamma surface for a solid-liquid-solid sandwich structure for (310) surfaces in delta-iron. The energy surface depends on the separation of the two grains (i.e. the melt layer thickness).
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