A process for manufacturing a hollow
pressure vessel, in which a billet is cast from an
alloy with a composition in % by weight, Zn=6.25-8.0, Mg=1.2-2.2, Cu=1.7-2.8, Fe<0.20, Fe+Si<0.40, at least one of the elements selected from the group consisting of Cr, Zr, V, Hf and Sc in an amount of 0.05-0.3, and other elements <0.05 each and <0.15 total. The cast billet is homogenized with a temperature profile such that
metal temperature is slightly less than incipient
melting temperature at all times, cooled to ambient temperature and
softening annealed for a duration of 20 to 40 h between 200 and 400° C. with cooling at a rate of less than 50° C. / h down to a temperature of below 100° C., resulting in a billet
hardness <54 HB. A
slug is
cut out of the softened billet, cold or slightly warm extruded with an
extrusion start temperature <300° C., to form a casing which is necked, solution
heat treated at a temperature slightly below the incipient
melting temperature, for a duration sufficient to obtain an absolute value of
specific energy associated with a DTA thermogram
signal of less than 3 J / g, quenched in cold water, and aged at between 100 and 200° C. for a duration between 5 and 25 h.