Vacancy-solute interaction in magnesium alloy WE54 during artificial ageing: a positron annihilation spectroscopy study

F. MOIA; A. CALLONI; R. FERRAGUT; A. DUPASQUIER; C. MACCHI; A. SOMOZA; J.F, NIE

ZEITSCHRIFT FUR METALLKUNDE

Carl Hanser Verlag GmbH & Co. KG

Año: 2009 p. 378 - 381

0044-3093

The vacancy–solute interaction during artificial ageing at250 8C was studied in the commercial alloy WE54 by coincidenceDoppler broadening of the positron annihilation radiation.The results show that in the initial state of ageingpositron trapping is weak. Under these conditions, the faintsignal comes predominantly from small Zr particles, withminor contributions from vacancy–Nd complexes. Positrontrapping increases concomitantly with the formationof the b’- and b1-phases at the onset of precipitation hardening,and becomes very intense at later ageing stages whenthe b1-phase is formed. The chemical composition in contactwith open-volume defects changes after 4 h of ageingwith a progressive enrichment in Mg, concomitant with ahardness increase. There is evidence for a prevalence ofNd over Y up to 24 h of ageing and then a prevalence of Yover Nd for 96 h (Y/Nd 9 3) when the b-phase is dominant.