Directionally solidified microstructures and peritectic phase growth of Cu-75%Sn peritectic alloy

Directionally solidified microstructures of Cu-75%Sn peritectic alloy were investigated at the growth rate ranging from 1 to 300 μm/s. With the growth rate increasing, directionally solidified plate-like microstructures in Cu-75%Sn peritectic alloy are refined by the increase of nucleation quantities of primary ε phases and cooling rate. Peritectic η phase can grow by the peritectic transformation and direct solidification from the liquid. At the low growth rate varying from 5 to 10 μm/s, the width of ε phase increases due to the effect of the peritectic transformation; however, at higher growth rate, the deviation between the width of ε phase and the whole plate-like microstructure increases resulting from direct solidification of η phase from the undercooled melt. The regressed data show that the relationship between the width of the whole plate-like microstructure (W) and the growth rate (v) satisfies as Wv^0.27 =117 μm^1.27·s^-0.27 and the primary dendritic arm spacing (λ) with the growth rate has a relation of λv^0.208 = 153.8 μm^1.208·s^-0.208 as the growth rate increases from 3 to 300 μm/s.