Characterization of Cu6Sn5 intermetallic powders produced by water atomization and powder heat treatment

Since the Cu6Sn5 intermetallic shows its importance in industrial applications, the Cu6Sn5 intermetallic-containing powders, produced by a powder processing route with a high production rate, were characterized. The route consisted of water atomization of an alloy melt (Cu–61 wt.% Sn) and subsequent heat treatment of the water-atomized powders. Characterization of the water-atomized powders and their heated forms was conducted by using X-ray diffraction, scanning electron microscopy and transmission electron microscopy. Fine water-atomized powder microstructures consisted of primary hexagonal η-Cu6.25Sn5 dendrites coexisting with interdendritic η-Cu6.25Sn5 + β-Sn eutectic. Solidification of fine melt droplets was governed by surface nucleation and growth of the primary hexagonal η-Cu6.25Sn5 dendrites followed by η-Cu6.25Sn5 + β-Sn eutectic solidification of the remnant liquid. In coarse melt droplets, nucleation and growth of primary ε-Cu3Sn dendrites were followed by peritectic reaction (ε-Cu3Sn + liquid → η-Cu6.25Sn5) or direct crystallization of η-Cu6.25Sn5 phase from the undercooled melt. Finally, the η-Cu6.25Sn5 + β-Sn eutectic solidification of the remnant liquid occurred. Heating of the water-atomized powders at different temperatures resulted in microstructural homogenization. The water-atomized powders with mixed phases were transformed to powders with single monoclinic ή-Cu6Sn5 phase.