Effects of Cooling Rate and Composition on Mechanical Properties of Directionally Solidified Pb100-x-Snx Solders

Pb100-x-Sn-x solders (x = 5 wt.%, 10 wt.%, 20 wt.%, 35 wt.%, 50 wt.%, 60 wt.%, 61.9 wt.%, and 95 wt.%) were directionally solidified upward over a wide range of cooling rates (T) over dot (0.016 K s(-1) to 4.0 K s(-1)) by using a Bridgman-type directional solidification furnace. Microstructure parameters (primary dendrite arm spacing, lambda(1), and eutectic spacing, lambda(E)) and mechanical properties (microhardness, HV, and ultimate tensile strength, sigma) of the Pb100-x-Sn-x alloys were measured. The dependences of the microhardness and ultimate tensile strength on the cooling rate, microstructure parameters, and composition were determined. According to experimental results, the microhardness and ultimate tensile strength of the solidified samples increase with increasing cooling rate and Sn content, but decrease with increasing microstructure parameters.