The type of layering in the photomicrograph is gneissic layering and The grains are quartz and feldspar.
The layers are formed by the alternating growth of the different phases.
In the photomicrograph, the eutectic layering is evident in the alternating light and dark bands.
The light bands are likely composed of a phase rich in the lower melting point alloying element, while the dark bands are likely composed of a phase rich in the higher melting point alloying element.
The specific phases that form in a eutectic alloy depend on the composition of the alloy and the solidification conditions. In the photomicrograph, it is difficult to identify the specific phases without additional information.
However, it is possible that the light bands are composed of a phase rich in aluminum, while the dark bands are composed of a phase rich in silicon.
Eutectic alloys are often used in applications where high strength and wear resistance are required. This is because the eutectic layering provides a fine dispersion of the different phases, which can hinder dislocation movement and grain growth.