MICROSTRUCTURE, TRIBOLOGICAL PROPERTIES, AND HARDNESS OF SPRAY-DEPOSITED AND WARM-ROLLED Al–Pb ALLOYS IN PERIPHERAL REGIONS

Abstract

The Al–18% Pb and Al–20% Pb alloys were processed by a rapid solidification, i.e., the spray deposition technique. The deposit in a shape of Gaussian curve, or bell-shaped deposit, was obtained at a pressure of 9 bar, nozzle-to-rotor distance of approximately 423 mm, and rotor inclination angle of 0°. From obtained spray deposits Al–18% Pb and Al–22% Pb, samples were cut down from the peripheral regions to portions 30 mm long and 20 mm thick. The samples were warm rolled at different percentages of thickness reduction, such as 0, 15, 30, 45, and 60%, at a recrystallization temperature of 0.4Tm. The value Tm refers to the melting point of the alloy at warm-rolled condition, i.e., 575 °C, which is evident from the Al–Pb phase diagram. As visible from the microstructure, Pb is equally distributed in the aluminum matrix in both spray deposit samples with up to 60% thickness reduction. With lower thickness percentage of warm-rolled specimens, the hardness values decrease in Al–18% Pb and Al–22% Pb alloys. Porosity is lower in Al–18% Pb alloy than that in Al–22% Pb alloy due to the deposition and rolling defects. The tribological tests showed that with the increase of Pb content from 18 to 22%, the wear rate increases abnormally, and the values of wear intensity and friction coefficient of the Al–22% Pb alloy are higher compared with those of the Al–18% Pb alloy.