On specifics of hardening mechanisms in metallic matrix composition"

Introduction. Functional properties of diamond powders are determined by a large-scale structural factor since it affects the formation of structurally sensitive mechanical properties — stress limit and yield value. Considering the qualitative correlation between yield value and hardness, it is possible to predict an increase in hardness including highly rigid materials.

Materials and Methods. Physical characteristics of the basic types of fillers that make up the reinforcers are considered, systematized and tabulated. M2-01 tin bronze (20 wt. % tin, 80% copper) was used as a bond. Ultradisperse natural diamond (UDND, 0.5-4 wt. %) was added to it, as well as powders of natural diamond (3/2 pm fraction, 7/5 pm, -40 pm) obtained through processing diamonds at the enterprise of “Sakha Daimond” JSC. The above materials were made on the crushing and screening equipment and shaking tables. The stages of obtaining powders were recorded using the raster electron microscopy. Vibroscreens were applied for the grain-size classification of diamond powders. Physical and mechanical characteristics of the produced samples were tested by standard methods. VLTE-500 electronic fourth-class laboratory balance was used for weighing. Density was determined by MK 0-25 mm micrometer according to GOST 6507-78.

Research Results. Porosity was calculated through the actual and theoretical density. It was found that with a decrease in the filler size, an improvement in the physicomechanical properties of the binder modified with a diamond powder is observed. The best performance was observed in the samples with the UDND filler.

Discussion and Conclusions. As a result of the study, it was recorded that the calculated data differ from the experimental data since they show an increase in the material hardening pro rata to the amount of the diamond particles introduced into the volume. An assumption has been made that the considered hardening model (Orowan model) does not take into account the formation of carbon and the agglomeration of diamonds into larger objects in the matrix volume under an increase in the number of input diamonds. If the UDND particle volume reaches 3%, the carbon con tent in the material increases. As a result, the filler particles are not fully oxidized, thus increasing the number of pores in the material.

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