Dry wear behavior and mild-to-severe wear transition in an Mg-Gd-Y-Zr alloy

Abstract

This paper describes the wear behavior, mild-to-severe wear transition (MSWT), analysis of microstructure and property underneath the wear surface for an Mg-10.1Gd-1.4Y-0.4Zr alloy within 0.2–4.0 m s−1 under dry sliding condition. The volumetric wear rate was plotted against applied load at each experimental speed. The worn surfaces were examined by SEM and EDS techniques, from which the wear mechanisms were identified, and they were used to draw a wear mechanism transition map with mild and severe wear regions. The results reveal that there exists a turning point on the wear rate-load curve under each sliding speed, which actually corresponds to MSWT. Two different types of MSWT are found in different speed ranges. The first one is controlled by a severe oxidation wear, and it operates within 0.2–0.5 m s−1, while the second one is controlled by a severe plastic deformation (SPD) wear, and it works within 0.8–4.0 m s−1. An analysis of microstructure and property underneath the worn surface proves that the mechanism for the second type of MSWT is the dynamic recrystallization (DRX) induced softening of surface material. With the help of DRX dynamics theory of metals, the critical surface DRX temperatures for MSWTs within 0.8–4.0 m s−1 are estimated, and from which the transition loads are evaluated according to a simplified modeling for MSWT load. There is a good agreement between the calculated and measured transition loads, indicating that SPD-controlled MSWT follows contact surface DRX temperature criterion.