During cooling and solidification of alloys it has been observed in time-based cooling curve charts (Fig. 1) (s. Thermal analysis) that the temperature remains constant for a longer period at certain points. These points are referred to as halts and originate from the fact that at those specific temperatures heat is released (during cooling) and heat is consumed (during heat-up).
For example, heat is released during solidification or during transition to solid condition by a change in the crystal structure, which effect causes the halts in the cooling curve. The halts are useful, for example for thermal analysis of the composition of an alloy.