The Researches On Microstrucres And Aging Characteristics Of Pb-Ca-Sn-Al-Ag-Ce Alloys

Lead acid batteries play an important role in transportation,national defense and military industry because of their advantages of high discharge voltage,low production cost,easier use in floating charge state,stable performance and so on.However,the low strength of the Pb base alloy grids and size growth during service often result in the fracture of the grid ribs and associated performance deterioration.In this paper,the aging behavior of Pb-Ca-Sn-Al-Ag-Ce alloys in different aged states was studied by hardness and resistivity measurements,and the microstructures of the alloys were characterized by SEM,XRD and OM.The effects of the paste curing on the hardness and microstructures of the alloys were also investigated.?1?During natural aging,the hardness of both the cast Pb-Ca-Sn-Al and Pb-Ca-Sn-Al-Ag-Ce alloys increase to the peak value at first and then remain stable.However,the time required for the alloys to reach the peak hardness is different.The hardness of both cast alloys increases after natural aging treatment and with the increase in aging time the resistivity of both alloys initially decreases to the lowest value and then tends to be stable.?2?For both alloys naturally aged after 230?,250?and 270?solid solution treatment,the hardness increases rapidly at first,reaches maximum and then keeps almost stable.However,the hardness decreases after the peak hardness and the time for reaching to the peak hardness is greatly shortened,when the two alloys are aged at 80?.The resistivity curves of the cast Pb-Ca-Sn-Al and Pb-Ca-Sn-Al-Ag-Ce alloys aged at 80?show a quick decrease in early stage and nearly unchanged afterwards.?3?In the two cast-natural aged alloys,square and rhombic particles of about 2?m in size were observed and verified by EDS analysis to be precipitates of(Pb_1-xSn_x)₃Ca rich in Sn and Ca elements.During aging after solid solution treatment at different temperatures,the quantities of rod-like and spherical(Pb_1-xSn_x)₃Ca increase significantly.The grains of Pb-Ca-Sn-Al alloys are very coarse and nevertheless the Pb-Ca-Sn-Al-Ag-Ce alloys have fine grains and uniform microstructure.On the other hand,with the increase of solid solution temperature the grain growth in the Pb-Ca-Sn-Al-Ag-Ce alloys is substantially slighter than that in the Pb-Ca-Sn-Al alloys?4?The paste curing process has very little effect on the hardness and microstructures of both cast-aged alloys.The hardness and microstructures of the two alloys after 230?solid solution treatment and natural aging have no obvious change after the paste curing process.