Based upon new results of the position of the upper limit of the α–α′ miscibility gap, the positions of the (i) metastable αm–α′m miscibility gap and (ii) chemical as well as coherent spinodal curves are recalculated. Furthermore, the position of the so‐called ‘spinodal of GP zones’ is determined by means of latest experimental data. It turned out that by use of the applied methods (i) all the calculated curves are in a “reasonable” order and (ii) the positions of the coherent spinodal curve and the “spinodal of GP zones” are not far from each other.