Soldering terminology

The behavior of a binary alloy of metals A and B is described by a state diagram derived from the cooling curves of the alloy first present as a melt. The illustration shows the cooling curves of the three alloys X, Y (eutectic) and Z, which all have different composition. For example, the points X _A and Z _B represent the intersections of the cooling curves of X and Z with the liquidus line (A'E and B'E). These are the temperatures at which the metals A and B begin to crystallize, that is, to form primary crystals. If a specific structure separates from another during the solidification process, solidification heat is released and, as a consequence, the slope of the cooling curve starts to decrease from this turning point, indicating the onset of crystallization.