Solidification structure characteristics and mechanical properties of (Ag-Cu₂₈)-25Sn alloy ribbons prepared by melt spinning method

To obtain novel intermediate temperature alloy solders with melting temperature of 400∼600°C, (Ag-Cu₂₈)-25Sn alloy ribbons were prepared by high frequency induction melting and melt spinning at different quenching linear speed. The effect of the development of solidification structure on melting properties and microhardness of the ribbons were investigated. The XRD results show that the as-prepared alloy ribbons have the same phase composition as the master alloy, which consists of Ag₄Sn and Cu₃Sn. With the quenching linear speed increasing, the solidification structures are refined and change from dendritic crystals to uniform granular crystals. As the quenching linear speed increases up to 32.25m/s, the grain size of the alloy ribbon has a distribution ranging from submicron to about 2μm. The DSC results indicate that the melting properties of alloy ribbons strongly depend on the solidification structure, and the melting temperature of alloy ribbons decreases with the quenching linear speed increasing. The lowest liquidus points of the alloy ribbon prepared at linear speed of 32.25m/s are located at 473.6°C and 524.7°C, respectively. The refined solidification structure notably increases the microhardness of the alloy ribbons, and the largest hardness value of 396H_V is obtained for the alloy ribbon prepared at linear speed of 32.25m/s, which increases 27.0% compared with the master alloy.