Thermodynamic Study On The Phase Equilibria In The Mg-Al-Zn-Ca-Sn System

As the lightest structural metal materials in the engineering application,magnesium alloys have been widely used for their numerous prominent characteristics.However,the low yield strength and poor high temperature resistance make it difficult to practical applications.In order to design alloy with better performance,reasonable alloy compositions and processing technology are necessary.It is vital to acquire precise phase diagram information and the thermodynamic database of magnesium alloys,which will provide theoretical references for practical researches.In this work,thermodynamic calculations are carried out by CALPHAD on the phase equilibria of the Mg-rich region of Mg-Al-Zn-Ca-Sn systems.The main results are described as follows:(1)The latest experimental data of the Mg-Al-Zn ternary phase diagrams and thermodynamic properties from literatures have been systematically collected and analyzed.The CALPHAD method has been used for the thermodynamic optimization procedure and the calculation of Mg-Al-Zn ternary system.Then the revised thermodynamic parameters of Mg-Al-Zn ternary system have been established.The calculated phase diagrams coincide well with experimental results.(2)Combined with the experimental phase diagrams of Mg-Al-Ca ternary system reported in the literatures,the parameters of this system have been revised and the isothermal sections of the Mg-Al-Ca system at 300?,400? and 500?have been thermody'namically calculated by CALPHD method.(3)Based on the thermodynamic assessments of Mg-Al-Sn,Mg-Sn-Zn,Mg-Sn-Ca,Mg-Ca-Znternary systems from the literature.Mg-Al-Zn-Sn and Mg-Al-Ca-Sn quaternary systems have been thermodynamically calculated.Furthermore,a thermodynamic database of Mg-Al-Zn-Ca-Sn system has been established,which will provide reliabletheoretical guidance for the alloy design of magnesium alloys.