An Investigation Of Impact Wear Behaviors Of AZ91D Magnesium Alloy In Dry Condition And In De-Ionized Water

Up to present, the surface damage of magnesium alloy under the conditions of both dynamic impact load and medium corrosion has not reported yet. In this study, the impact wear behaviors of AZ91D magnesium alloys in dry condition and de-ionized water were contrastively investigated, and the damage mechanisms were discussed. Further, the factors of influencing the impact wear properties were discussed. Therefore, the study has both practical significance and academic valueThe impact wear tests of AZ91D magnesium alloy in dry condition and de-ionized water had been performed by the impact tester. The influences of load (20 N and 40 N) and impact number (1×10~4 to 5×10~5) on impact wear behavior had been systemically investigated. The impact wear spots were measured and analyzed by means of optical microscope (OM), laser confocal scanning microscope (LCSM), X-ray diffraction (XRD), scanning electrical microscopy (SEM), energy dispersive spectroscopy (EDX) and surface profiler. Main conclusions are drawn as follows:1. In dry condition, the impact wear mechanism of AZ91D magnesium alloy was fatigue. The depth and area of the wear scar increased slowly with increasing impact number. The damage of AZ91D magnesium alloy at the initial stage was characterized by cyclic plastic deformation, then the phenomenon of adhesive wear and bit delamination appeared because of work-hardening of surface layer. The rate of depth increment was depressed. Finally, the plastic of surface layer exhausted and fatigue crack occurred, the spreading and joining of cracks would cause the failure of the material as big delamination.2. In de-ionized water, the wear mechanism showed as the mutual accelerating of fatigue delamination and corrosion. The depth and area increased rapidly with increasing impact number. At the initial stage, the wear damage of AZ91D magnesium alloy was characterized by cyclic plastic deformation and adhesive wear. With the increase of impact number, fatigue cracks occurred in the surface and sub-surface. The corrosive wear of the material became heavier after the crack appeared. The de-ionized water penetrated into the cracks, on one hand, it had an corrosion effect upon the AZ91D magnesium alloy, on the other hand, it could cause point corrosion, and thus the wear material was characterized by deep brittle spalling; meanwhile, a film appeared on the surface, but it would be destroyed and created circularly by the impact load, and thus the wear depth increased significantly. In a word, the cracks proliferated and spread rapidly by the impact load together with corrosion, , and the damage of AZ91D magnesium alloy was severe.3. Under the impact load of 20 N and 40 N, the wear depth and area and its growth rate of AZ91D magnesium alloy in de-ionized water were larger than that in dry condition. The impact wear resistance of the AZ91D magnesium alloy decreased in de-ionized water. De-ionized water did not play a role of lubricating and reducing the wear degree, contrastly, it brought corrosion mechanism on the worn surface, the impact wear and surface corrosion promoted mutually and accelerated the wear damage and failure of material.