Thermodynamic criterion of Spinodal decomposition aging in the (γ＋α) metastable miscibility gap inγ Mn-Cu alloys

Sub-regular solution model is used to calculate the thermodynamic ofγ Mn-Cu alloy. It is revealed that there exists Spinodal decomposition in (γ＋α ) metastable miscibility gap. For the Mn-Cu alloy with composition of 60～ 90 at％ Mn Spinodal decomposition will occurs during aging at 400～ 600oC. The Spinodal decomposition range measured by TN point is more reliable than by hardness.