eutectic images

eutectic

Substance X consists of two components, A and B (approximately 80% A and 20% B). Above the liquidus (the temperature at which the first solid begins to form) both components are liquid. As the temperature drops to the liquidus, component A starts to solidify, and the remaining liquid becomes less rich in component A and more rich in component B.

When the temperature has dropped to the solidus, which is the same as the eutectic temperature, solid B starts to form as well.

Below the solidus, the entire mixture is solid. A liquid of composition Y (consisting of approximately 80% B and 20% A) would cool in a similar manner, but with solid B forming first. A mixture of eutectic proportions is always either entirely solid or entirely liquid.