Preparation and characterization of nanocrystalline (Ag-Cu₂₈)-25Sn alloy powder

Nanocrystalline (Ag-Cu₂₈)-25Sn alloy powder was prepared by mechanical alloying (MA). The phase composition, microstructure and melting properties of the as-milled alloy powder were studied by XRD, SEM, HRTEM and DSC. The results show that the phase composition of nanocrystalline (Ag-Cu₂₈)-25Sn alloy powder is Cu₃Sn and Ag₄Sn phase. After milled for 40 h, the alloying process is completed and the melting temperature of the as-prepared alloys is 548. 5°C. With the milling time increasing to 60 h, the alloy becomes amorphous obviously whose melting temperature is 554.0°C. The melting zone reduces and there are two clear exothermic peaks at 186.3°C and 399. 5°C in DSC curve. Moreover the HRTEM result indicates that the nanocrystalline size is from 5 nm to 10 nm and there are amorphous phases and lattice defects in alloying process. The average grain sizes of as-prepared alloys annealed at 200°C and at 400°C are 21.3 nm and 33.9 nm, respectively.