Effect of High-Temperature Pulsed Deuterium Plasma on the Structure and Mechanical Properties of the Surface of Cu–Ga and Cu–Ga–Ni Alloys
The changes in the mechanical properties and the texture of the surface layers in Cu–10Ga and Cu–10Ga–4Ni alloys are studied under the powerful pulsed radiation-thermal and shock-wave loads characteristic of pulsed thermonuclear fusion plants. Samples are irradiated by pulsed high-temperature plasma and ions in the 600-kJ Plasma Focus (PF) PF-1000 (Poland) plant, and deuterium is used as a working gas. The deuterium plasma power density is varied from 107 to 109 W/cm2 at the plasma pulse duration of ~10–7 s, and the deuterium ion flux power density is from 108 to 1011 W/cm2 at an ion flux incident time of ~5 × 10–8 s. Irradiation under the experimental conditions is found to change the texture of the surface layers to a depth of several micrometers, which is likely to be caused by directional solidification at a high temperature gradient oriented normal to the irradiated sample surface. There is a correlation between the type of texture formed in this case and the character of propagating slip lines with formation of a block structure. The lattice parameter in the irradiated surface layers decreases, which is related, supposedly, with the action of residual macroscopic stresses, since substantial changes in the surface layer composition have not been observed. A general tendency toward a decrease in the Vickers microhardness is noted in copper alloy samples as a result of their irradiation in the PF plant under the experimental conditions. A possible cause is thermal effect, since the concentration of alloying elements in the alloys decreases insignificantly after irradiation. The elastic modulus E of the Cu–10Ga alloy decreases insignificantly (to 14%) after irradiation. At the same time, in the Cu–10Ga–4Ni alloy, i.e., after alloying of the Cu–10Ga alloy with nickel (element with higher E as compared to that of copper), the elastic modulus of the initial surface layer remains almost the same after irradiation in PF.