Explanation

Transition phase between unstable phase (unstable phase) and stable phase (balanced phase). The stability of phase is determined by the value of its free energy. The free energy of the balanced phase (with certain chemical composition and crystal structure) is the smallest, the free energy of the unstable phase is the largest, and the free energy of is between the two. The free energy also corresponds to the minimum value of free energy, but not the minimum value. The equilibrium phase is the minimum value. The appearance of phase transformation is the result of spontaneous optimization of dynamics. To form a stable equilibrium phase, the driving force of phase transformation is the largest. Although the driving force is smaller than that of the equilibrium phase, the speed of forming metastable phase may be faster. In many cases, the nucleation rate of is far greater than the nucleation rate of the equilibrium phase, leading to the formation of the equilibrium phase before, and some may not continue transformation.

Classification