Effects of Li on microstructure and friction and wear behavior of 7075 aluminum alloy for drill pipe

Abstract

7075-(0%, 0.5%, 1%, 2%, mass fraction)Li alloy was prepared by hot pressing sintering, and the effects of Li on microstructure and friction and wear behavior of 7075 Al alloy were investigated. The results show that the density of 7075-0.5Li alloy reaches above 99% at sintering pressure of 60 kN. Al alloy consists of α-Al, η and S' phases. With the increase of Li content to 2%, the η phase decreases, δ' and δ phases increase, but α-Al is still the main phase. The hardness and wear rate of Al alloy are 71.25HV and 3.50×10-3 mm3·N-1·m-1, respectively. As the Li content increases, the hardness of Al-Li alloy decreases and the wear rate increases. However, 7075-0.5Li exhibits higher hardness and lower wear rate than those of Al alloy. Both oxidation wear and adhesion wear occurs in 7075-Li alloy. With the increase of Li content, the η phase is reduced, the hardness decreases, the brittleness of Al2O3 is high which has a weak bonding with the matrix, and the dendrite spacing of microstructure widens, resulting in the transition from the abrasive wear to adhesive wear of the alloy, and therefore the wear resistance gradually decreases. Compared with Al alloy, 7075-0.5Li alloy prepared by hot pressing sintering shows a better wear resistance.

Keywords

• hot pressing sintering
• al-li alloy
• microstructure
• wear behavior