The AuSn phase diagram

The gold-rich side of the AuSn system has been examined using differential thermal analysis, differential scanning calorimetry and electron probe microanalysis. The presence of three intermetallic phases, β, ζ and ζ′, between gold and AuSn has been verified, although the composition ranges reported here are significantly different from those of previous studies. The resulting proposed AuSn phase diagram contains six intermetallic compounds and seven invariant reactions. Within the gold-rich region of the diagram there are four invariant reactions that occur: peritectics at 532 and 521 °C, a eutectic at 280 °C and a peritectoid at 190 °C, below which ζ′ is stable. The solubility range of tin in the ζ phase at 280 °C is 9.5–17.6 at. % Sn and in the β phase is 8.25–9.11 at.% Sn at the same temperature.