Abstract
Abstract
Conventional and natural materials, limited in quantity or for which high energy consumption is required, are increasingly being replaced by composite materials, as a very good alternative to the exploitation, energy and environmental problems caused by the production of classic. The relative shape and dimensions of the reinforcing component as well as the structure delimit the composite materials reinforced with particles, the filamentary composite materials and the stratified ones. The general properties of the composite materials are decisively influenced by the nature and properties of the constituents, by the volumetric fraction of the reinforcing component and by its orientation in the composite material, as well, as by the mechanical strength of the matrix - fiber/particle interface. The pieces sintered from metallic powders have special physical and chemical characteristics, determined both by the composition and structure of the existing phases, as well as by the size, shape and distribution of the grains. This paper aims to highlight the particularities of the process of obtaining by sintering a category of composite materials with the copper matrix as well as their characterization with regard to the physical-mechanical properties acquired as a result of sintering. Thus, for the production of parts with advanced compactness, the process of double pressing and double sintering is applied. The first pressing is performed with moderate pressures (3000 daN/cm2) and the sintering, at 800°C, with a bearing of about 30 minutes. The second pressing is performed at high pressures (5000 ÷ 6000 daN/cm2) and is followed by the final sintering, under normal regime. Regarding the sintered metal composite materials, with the role of friction, the most important mechanical property is the hardness. This is a function of the bonding forces between the particles, density and degree of resistance of the material at the test site and can be determined by the Brinell method.