We study specific features of the formation of micro- and nanostructures in diamond−Fe-Cu-Ni-Sn- CrB2 composite materials obtained by sintering in the molds placed in a muffle furnace with subsequent hot post-pressing. We also clarify the mechanisms contributing to the improvement of the mechanical properties of these composites depending on the technological modes of their production. Composite diamond-containing materials (DCM) on metallic binders, containing iron, copper, nickel, and tin, are extensively used in the production of cutting wheels, rope saws, core bits, and grinding and polishing tools with different areas of application (1). For the efficient sintering of these DCM, it is necessary to under- stand the processes running between the elements, including the interaction of diamond (carbon) particles formed in the process of graphitization of the surface with the α -Fe solid phase (2). In the present work, we develop the foundations of scientific analysis of the mechanisms promoting the improvement (or deterioration) of the structure of diamond-matrix transition zone and the mechanical properties of DCM obtained by sintering in the molds placed in a muffle furnace with subsequent hot post-pressing. It is shown that, unlike the DCM produced by using industrial technologies, the main causes of improvement of the mechanical characteristics of DCM obtained under the optimized conditions are the presence of Fe3C interlayers of nanosize thickness and the absence of graphite inclusions in the transition zone of these materials. It is also proved that the key factor for getting commercially promising DCM is the possibility of control of the diffusion of carbon (formed as a result of graphitization of the diamond surface in the stage of sintering of compositions in the furnace) into the crystal lattice of α -Fe in the course of their hot post-pressing. To improve the structure of these materials and endow them with certain specific properties, it is customary to introduce admixtures of borides, carbides, and silicides of transition metals, which can guarantee the for- mation of phases more stable than Fe3C in the transition zone (3, 4). The application of these admixtures often leads to the contamination of the transition zone with reaction products, which leads to structural instability and deteriorates the properties of DCM. The regularities of structure formation in systems with solid admixtures are not studied. This is explained by the absence of phase diagrams, mutual influence of the elements, very low concentrations of carbon formed in the course of graphitization of diamonds, and nonisothermal conditions of sintering. At the same time, the theoretical analysis of this problem is extremely complicated. However, the successful determination of the type of admixtures to the composition of the original mixture and the technolog- ical mode of sintering (P−T−t) is one of the main ways in the development of DCM with high technological characteristics. All these facts are important both for the theoretical sciences (verification of the already developed