| Abstrakt: |
1.The peculiarities of thermal fatigue of heterogeneous and composite metallic materials, whose matrices contain inclusions of varying nature (intermetallic compounds, intermetallic phases, metals) and type (particles, lamellas, fibers, wire, coatings), determine the cyclic structural stresses interacting with the stresses induced by the applied load. The level of the structural stresses depends on the physicomechanical properties, type, size, shape, volumetric proportion, nature of distribution of the inclusions, and also on the intensity of the thermal cycling.2.The structural stresses in thermal cycling in materials containing high-strength, finely dispersed incoherent inclusions (nitrides, oxides, carbides, silicates, sulfides, nickel aluminides, etc.) are associated chiefly with the difference between the coefficients of thermal expansion of the inclusion and the matrix in the temperature interval.3.With large inclusions of low strength (graphite, slag, pores), the structural stresses in thermal cycling are caused mainly by the difference between the coefficients of thermal expansion of the inclusion and the matrix.4.The greatest influence on thermal fatigue of heterogeneous materials is exerted by inclusions of nitrides, the smallest by inclusions of sulfides, and in the case of composite materials by fibers and particles of high-melting oxides.5.The obtained relationships for determining the level of cyclic stresses in thermal cycling enables us to evaluate the thermal-fatigue strength of heterogeneous and composite materials by a single method based on the characteristics of thermal fatigue of the matrix metal. |
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