The microstructure and mechanical properties of Zn-25Sn-XAl (X=0-0.09Â wt%) high temperature lead free solder

The microstructure and mechanical properties of Zn-25Sn-XAl ( X=0, 0.01, 0.03, 0.05, 0.09 wt% ) high temperature Pb-free solders were investigated. The addition of Al tends to refine the grain size and depress the undercooling behavior of the solder. The needle-like zinc-rich phase of the eutectic region was coarsened upon Al addition. The increasing addition of Al up to 0.09 wt% enhanced the ultimate tensile strength (UTS) of the alloy from 67.28 to 78.61 MPa (16.84% improved), and the yield strength from 42.52 to 52.81 MPa (24.2% improved). The strain of the solder degraded from 39.02-32.83% when the addition of Al ranged from 0 to 0.09 wt%.