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

摘要

Directionally solidified microstructures of Cu-75 percent Sn peritectic alloy were investigated at the growth rate ranging from 1 to 300 mu m/s. With the growth rate increasing, directionally solidified plate-like microstructures in Cu-75 percent Sn peritectic alloy are refined by the increase of nucleation quantities of primary e phases and cooling rate. Peritectic y phase can grow by the peritectic transformation and direct solidification from the liquid. At the low growth rate varying from 5 to 10 mu m/s, the width of e phase increases due to the effect of the peritectic transformation; however, at higher growth rate, the deviation between the width of e phase and the whole plate-like micro-structure increases resulting from direct solidification of 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 mu mLZ7 centre dot s~(0.27) and the primary dendritic arm spacing (A) with the growth rate has a relation of gamma m~(0.28) = 153. 8 gamma m~(1.27) centre dot s~(0.208) as the growth rate increases from 3 to 300 mu m/s.