One commonly used method for characterizing the dynamic characteristics of materials is the Taylor impact test. This method measures the dynamic yield strength of cylindrical specimens and determines material model constants required for the numerical simulation of the behavior of materials subjected to high-velocity deformation. The purpose of this work is to investigate the microhardness and microstructure of copper specimens at different impact velocities using the Taylor impact test. This paper describes experiments performed on copper specimens (OFHC 99.9%, M1) using a single-stage light-gas gun with impact velocities in the range of 150–450 m/s. After impact, the specimens were cut along the symmetry axis to measure the microhardness and the grain size of the microstructure. Microhardness in the entire area exceeded the initial value for all investigated velocities. The averaged microhardness curves were obtained for each specimen to identify four deformation zones and determine their dimensions depending on the impact velocity. The average grain size in the entire deformed specimen became smaller than in the starting specimen. The study of the microstructure of the specimens has shown that the grain size distribution corresponds to the four deformation zones in the copper specimens.
Introduction. One of the commonly used methods for assessing the dynamic characteristics of a material is the Taylor test, which establishes the relationship between the dynamic yield strength of a cylindrical sample material and its length after hitting a non-deformable barrier. The purpose of this work was to study the microhardness and determine the dynamic yield strength of copper samples for various impact velocities in the Taylor test.Materials and Methods. Experiments were carried out with cylindrical copper (M1) samples. The throwing conditions were selected on the ballistic stand, which provided the speed of the sample in the range of 150–450 m/s at the exit from the barrel. After the impact, the microhardness of the samples in the section plane was measured. The calculation of the dynamic yield strength was carried out according to the classical Taylor formula.Results. Experimental data are presented for cylindrical copper samples upon impact on a rigid wall with velocities in the range of 162–416 m/s, including configurations and sizes of images before and after impact. Microhardness distributions in the axial section of the samples were obtained. For each sample, the dependences of the averaged values of microhardness were constructed, which made it possible to identify four areas of deformation of the samples (the area of elastic deformations, plastic deformations, intense plastic deformations, the area of the material undergoing destruction) and determine their sizes. The dynamic yield strength of copper in the studied range of impact velocities was calculated.Discussion and Conclusions. The values of microhardness in the entire considered region and for all studied impact velocities exceeded the initial value. There was a significant increase in the value of the dynamic yield strength compared to its static value. The correlation of the maximum averaged values of microhardness and dynamic yield strength, which grew with increasing impact velocity, was identified.
Thermography and powder x-ray diffraction analysis were employed to examine hightemperature synthesis of nickel aluminide Ni 3 Al based intermetallic composite materials by the thermal shock of a powder mixture of pure elements with an inert filler. The influence of the inert component on the phase composition of the final product of the synthesis reaction is studied. The final product is assumed to be formed owing to reaction diffusion at the stage of cooling of the thermoreactive powder system. Thermokinetic constants of formation of the NiAl and Ni 3 Al phases are estimated. Regions of optimum regimes of high-temperature synthesis of the intermetallide Ni 3 Al are determined.
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