Characterization of the chemical vicinity of open volume defects in magnesium and AZ31 with coincident Doppler broadening spectroscopy

Abstract

AbstractMagnesium alloys experience an increasing interest for industrial applications due to their low specific weight, high elasticity and mechanical strength. For the high performance of these materials a homogeneous distribution of the alloy constituents is required. Therefore it is of great interest to investigate the behaviour of the elemental distribution in the vicinity of open volume defects. In order to investigate the influence of defects and their chemical surrounding, polished and annealed samples of pure magnesium and the alloy AZ31 (3 wt.% Al and 1 wt.% Zn) were irradiated with Zn, Al and Mg ions respectively. The energy of the ions was chosen between 1.4 MeV and 3.0 MeV according to 2.3 µm mean implantation depth. First, Doppler‐broadening measurements as a function of the positron implantation energy as well as lateral position with a resolution of 2 mm were recorded in order to image the irradiated area on the sample. Secondly, coincident Doppler‐broadening spectra were measured at different positron penetration depths according to the Makhovian profile, which clearly show strong deviations depending on the ion type of the irradiated samples. The relation between elemental signature and defect concentration in the sample is discussed. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)