Continuous Precipitation 上游充通大兽 SHANGHAI JIAO TONG UNIVERSITY Transition phases(过渡相) Transition phases form because they have a lower activation energy barrier for nucleation than the equilibrium phase. ■ Crystal structures of the transition phases are intermediate between those of the matrix and the equilibrium phase>a higher degree of coherence a low interfacial energy contribution to AG*. The equilibrium phase:complex crystal structure>incompatible with the matrix Longer time Total needed △G Free energy size -h G oa+GP GP a,+GPa G2 G3 g+8 Time (a) (b) Fig.5.28 (a)The activation energy barrier to the formation of each transition phase is very small in comparison to the barrier against the direct precipitation of the equilibrium phase.(b)Schematic diagram showing the total free energy of the alloy v.time. K.Chen 10K. Chen Continuous Precipitation 10 Transition phases (过渡相) Transition phases form because they have a lower activation energy barrier for nucleation than the equilibrium phase.  Crystal structures of the transition phases are intermediate between those of the matrix and the equilibrium phase  a higher degree of coherence  a low interfacial energy contribution to ΔG*.  The equilibrium phase: complex crystal structure  incompatible with the matrix Longer time needed