STRUCTURAL HARDENING MECHANISM OF LEAD-ST RONTIUM (TIN) ALLOYS FOR BATTERYS GRIDS .2. LEAD-STRONTIUM-TIN ALLOYS

The reequilibration of the ternary Pb Sr Sn alloys is studied at the s ame temperatures, by the same methods and in the same structural state s as was done previously for the binary Pb Sr alloys (1). The levels o f Sr are 0.10 and 0.25 % and those of Sn are located between 0.65 and 7.50 %. At a constant level of 0.10 % Sr and increasing tin levels the hardening by discontinuous transformation changes into a hardening by continuous precipitation near 0.40 % Sn. In all cases the hardening p rocess is followed by an overaging which consists of a discontinuous t ransformation with a lamellar reprecipitation of the (Pb-1-x Sn-x)(3) Sr phase from the fine hardening precipitates of the same phase. The a ddition of tin increases the hardening but favours the overaging.