《Transmission electron microscopy study of age hardening in a Mg-5 wt.% Zn alloy》.pdf

TRANSMISSION ELECTRON MICROSCOPY STUDY OF AGE HARDENING IN A Mg-5 wt.% Zn ALLOY* J. B. CLARK t In the temperature range from 149 to 26O”C, the Mg-5 wt. ‘A Zn alloy age hardens by the precipitation of a coherent transition lattice, MgZn’, in the form of long thin rods perpendicular to the basal plane. At temperatures below 149”C, formation of G.P. zones hardens the alloy after very long aging times. Upon loss of coherency, the MgZn’ rods transform to idiomorphs of the equilibrium MgZn phase. Basal slip and 1012 twinning are the principal deformation modes between 25 and - 196°C. A small temperature dependence of the flow stress was observed. 1012 twinning shears the MgZn’ rods, but slip dislocations bow between the widely spaced (1000-2000 A) MgZn’ precipitates. Thus precipitation of MgZn’ produces only a moderate increase in strength. ETUDE PAR MICROSCOPIE ELECTRONIQUE PAR TRANSMISSION DU DURCISSEMENT D’UN ALLIAGE Mg-5% Zn Dans la gamme de temperatures entre 149 et 26O”C, l’alliage Mg-Zn 5 % durcit par transformation d’une phase de transition cohente MgZn’. Celle-ci a la forme de longues aiguilles minces apparaissant perpendiculairement au plan de base. Aux temperatures inferieures iL 149”C, la formation de z8nes de G.P. durcit l’alliage aps