Structure, Mechanical Properties and Friction Characteristics of the Al-Mg-Sc Alloy Modified by Friction Stir Processing with the Mo Powder Addition

Abstract

In this study, samples of Al-Mg-Sc alloy were investigated after friction stir processing with the addition of Mo powder. Holes were drilled into 5 mm-thick aluminum alloy sheets into which Mo powder was added at percentages of 5, 10, and 15 wt%. The workpieces with different powder contents were then subjected to four passes of friction stir processing. Studies have shown that at least three tool passes are necessary and sufficient for a uniform Mo powder distribution in the stir zone, but the number of required passes is higher with an increase in the Mo content. Due to the temperature specifics of the processing, no intermetallic compounds are formed in the stir zone, and Mo is distributed as separate particles of different sizes. The average ultimate strength of the composite materials after four passes is approximately 387 MPa in the stir zone, and the relative elongation of the material changes from 15 to 24%. The dry sliding friction test showed that the friction coefficient of the material decreases with the addition of 5 wt% Mo, but with a further increase in Mo content, returns to the original material values.

Keywords

• friction stir processing
• aluminum alloys
• tribology
• microhardness
• microstructure
• mechanical properties