The T-x-y-z diagrams of quaternary Na2MoO4-Na2CrO4-Na2WO4-Na2SO4, Fe-Ni-Co-Cu, Pb-Cd-Bi-Sn systems and their four-dimension (4D) computer models are considered. Geometric constructions of these diagrams are described by special di-, uni- and invariant states schemes. Assumed liquidus of the Fe-Ni-CoFeS-NiS-CoS subsystem T-x-y-z diagram on the basis of the data about the structure of the border systems is predicted and the 4D computer model is designed. The possibilities of calculating of three- (3D) and two-dimensional (2D) iso- and polythermal sections are shown. 

Graphical Abstract

T-x-y-z phase diagrams assembling: Na2MoO4-Na2CrO4-Na2WO4-Na2SO4, Fe-Ni-Co-Cu, Pb-Cd-Bi-Sn, Fe-Ni-Co-FeS-NiS-CoS