Variation in the Stress State of Copper Alloys Under the Action of Cold Air Plasma
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Journal of Engineering Physics and Thermophysics, Vol. 93, No. 6, November, 2020
TRANSFER PROCESSES IN LOW-TEMPERATURE PLASMA VARIATION IN THE STRESS STATE OF COPPER ALLOYS UNDER THE ACTION OF COLD AIR PLASMA A. G. Anisovich,a I. I. Filatova,b and S. V. Goncharikb
UDC 669.2.017:620.18+621.039.6
An investigation has been conducted into the action of nonequilibrium low-temperature plasma of a high-frequency capacitive discharge in air at a pressure of 133.3 MPa upon the structure of brass and beryllium bronze. The absence of changes in the microstructure of alloys under the action of plasma was established using the target metallography method. It has been shown that the main effect of the plasma action is the formation of static distortions of the abovementioned materials at the level ~0.007·10–10 m. Keywords: nonequilibrium low-temperature plasma, microstructure, static displacement, copper alloys, stress state. Introduction. In traditional, classical methods of treating metals and alloys, the stress state of materials whose change makes it possible to judge about the kinetics and mechanisms of structure formation processes, is of key significance. In plastic deformation and heat treatment of metals and alloys, the change of their structure at the microlevel is accompanied by the change of stresses of the first kind (macrostresses) and/or stresses of the second kind (microstresses). Issues connected with the change in the stress state of materials and products have been studied to date in great detail in accordance with practice requirements. Macro- and microstresses differ in the scale of volumes in which they are localized. Stresses of the first kind are brought to equilibrium in the volume of a sample or product and are the cause of the disruption in its dimensional stability. These stresses are detected by the angular displacement of the interference lines of the sample X-ray photograph. Stresses of the second kind are brought to equilibrium in the grain volume or in the volume of a polycrystalline sample polygonal block and are connected with the change in the concentration of defects in the crystal structure (mainly, of dislocations). These stresses are detected by the widening of the interference lines in the sample X-ray photograph [1]. Macro- and microstresses can be manifested jointly [2]. It is possible to use X-ray graphical data on lattice distortions occurring under plastic deformation to estimate the internal stresses corresponding to them [3]. The energy of elastic stresses is calculated by the formula 2
ΔU =
1 1 ⎛ Δd ⎞ Eλ2 = E ⎜ ⎟ , 2 2 ⎝ d ⎠
(1)
where Δd is determined by the value of the displacement of the interference lines (for stresses of the first kind) or by the value of the widening of the lines (for stresses of the second kind) in the sample X-ray photograph. Calculation by this formula yields the value ΔU = 0.015 cal/g (for copper) for the energy of stresses of the second kind, which is equal to several percent of the energy absorbed by the deformed metal. The change in the level o
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