Evolution of primary phases and high-temperature compressive behaviors of as-cast AuSn20 alloys prepared by different solidification pathways

Abstract

The as-cast AuSn20 eutectic alloys prepared by four different solidification pathways have been investigated in terms of the microstructure and the high-temperature compressive behaviors. The primary phases appeared in the four alloys are very sensitive to the cooling rate, which decrease in the size and the volume fraction as the cooling rate increases. The morphologies of the primary ζ′-Au5Sn phase are in dendritic at low cooling rate and change to rosette-like at high cooling rate. When the cooling rate is about 3.5 × 104 K/min, the primary ζ′-Au5Sn can be suppressed but small δ-AuSn particles appear instead as the primary phase. The compressive behaviors at 220°C exhibit a low yielding stress and a long stress platform for the alloy prepared by injection casting with a copper crucible, which indicates an advantageous processing route for the production of the AuSn20 strips or foils.