Determination of an Equilibrium Phase Diagram

DTA is a useful method for measuring an equilibrium phase diagram. For example, in order to establish a Gd-Co phase diagram, transformation temperatures of Gd,Co are determined by DTA. The measuring method is as follows  

A specimen of mass 50 g is placed in an AljO, crucible with a flat bottom and a volume of 0.6 ml. The reference crucible is empty. 

The furnace of the DTA is evacuated to 10 Pa, then argon gas is passed through the furnace, followed by evacuation again. This process is repeated twice to eliminate any remaining active gas. 

The temperatures of phase transformations are measured at a heating rate of 10 or -lOKmin.  

The enthalpy H of a liquidus alloy consisting of A and B is not equal to the sum of (enthalpies of elements A and B, respectively). During the formation of a liquid, mixing of different atoms leads to energy absorption or release (mixing enthalpy, If it is assumed 

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