The subsurface zone in magnesium alloy studied by positron annihilation techniques

This paper presents the positron lifetime and Doppler broadening of annihilation line studies of the subsurface region in a magnesium-based alloy which was exposed to dry sliding. The total range of the subsurface zone below the worn surface detected using these techniques was lower than 100 μm and was hardly affected by the applied load and sliding distance. The obtained results are significantly different from the results achieved for pure magnesium, thus alloying has considerable effect on the subsurface zone formation. The positron lifetime profile of the subsurface region was well correlated with the microhardness profile. The significant result was that the weak long-lived component indicated ortho-positronium formation has been found at the depth lower than 30 μm. This indicates the formation of voids below the worn surface.