先进材料疑固实验室 Equilibrium state Laboratory of Advanced Materials Solidification Definition of equilibrium state The real solidification is never equilibrium.But in most case,to simplify mathematical calculation,it is assumed that there is a local equilibrium can be achieved at S/L interface. This assumption can be used in liquid metal solidification in conventional casting and welding. This assumption means it is able to figure out the solid and liquid composition at the interface use equilibrium phase diagram. But this doesn't means the system is equilibrium because in the system there are temperature and composition gradient. 上浒充通大学 SHANGHAI JIAO TONG UNIVERSITYEquilibrium state Definition of equilibrium state • The real solidification is never equilibrium. But in most case, to simplify mathematical calculation, it is assumed that there is a local equilibrium can be achieved at S/L interface. • This assumption can be used in liquid metal solidification in conventional casting and welding. • This assumption means it is able to figure out the solid and liquid composition at the interface use equilibrium phase diagram. • But this doesn’t means the system is equilibrium because in the system there are temperature and composition gradient