PHYSIO - ELECTRICAL CHARACTERISTICS OF Sn/Pb SOLDER AFFECTED ALUMINUM SUBJECTED TO PLASTIC DEFORMATION AND THERMAL TREATMENT

Abstract

In the present work, the precipitation behaviour of solder affected Al - Sn - Pb alloy is investigated as a function of cold deformation and artificial ageing using microhardness measurements, electrical resistivity, differential scanning calorimetry, X-Ray diffraction analysis as well as microstructural observation. To compare the aforementioned properties three different types of aluminium have been selected for analysis: commercially pure aluminium, binary aluminium with tin, and binary aluminium with lead. It has been found that changes in such parameters like cold rolling and thermal treatment play a crucial role in influencing the physio-electrical qualities of alloys. The alloys exhibit two distinct processes: solid solution strengthening combined with strain hardening resulting from cold plastic deformation, and the softening mechanisms of recovery and recrystallization. The presence of solder positively influences the hardness of pure aluminium at lower aging temperatures, primarily due to solid solution strengthening from tin and lead, albeit at the cost of conductivity. The superior performance of BCC tin over the similar FCC lead structure to Al is attributed to its unique crystal structure. Furthermore, neither of the two elements forms any intermetallic with Al, while Sn and cast alloy impurities do form a variety of intermetallic. DSC and XRD study also confirm the presence of those elements. The micrographs study of cold rolled alloys has confirmed elongated grain at the rolling direction and relatively thick grain boundaries of minor alloying elements due to the presence
of different particles. All the alloys attain more or less re-crystallized state after ageing at 350^oC for one hour.