LAUSR

Gold80–tin20 (Au80Sn20) eutectic alloy with coarse primary ζ'-phase and irregular eutectic structure is intrinsically brittle. In this study, various processes were applied to prepare Au80Sn20 alloy. The effects of suction casting processing parameters on the solidification structure, indentation hardness, and modulus were investigated, and the underlying mechanism was discussed. Results showed that the conventionally cast microstructure was made up of coarse dendritic ζ'-Au5Sn (primary phase) and (ζ'-Au5Sn and δ-AuSn) eutectic structure; however, in rapid solidification process size of the primary phase decreased from 200 μm to approximately 10 μm. Moreover, when the current of arc-melting was increased, size of the primary phase continuously shrunk to approximately 3 μm, leading to the change in the morphology from fine dendrites to dots-like. Moreover, volume of the primary phase was correspondingly reduced as the lamellar spacing decreased from 500 ± 50 nm to 150 ± 10 nm. The two-phase orientation relationship of lamellar eutectic was Besides, hardness of the Au80Sn20 eutectic alloy increased from 1.67 to 2.17 GPa, and the modulus increased from 70.67 to 83.17 GPa with increasing suction casting current.