The rapid solidification behavior of Co-Sn al- loys was investigated by melt spinning method. The growth morphology of αCo phase in Co-20%Sn hypoeutectic alloy changes sensitively with cooling rate. A layer of column...The rapid solidification behavior of Co-Sn al- loys was investigated by melt spinning method. The growth morphology of αCo phase in Co-20%Sn hypoeutectic alloy changes sensitively with cooling rate. A layer of columnar αCo dendrite forms near the roller side at low cooling rates. This region becomes small and disappears as the cooling rate increases and a kind of very fine homogeneous microstruc- ture characterized by the distribution of equiaxed αCo den- drites in γCo3Sn matrix is subsequently produced. For Co-34.2%Sn eutectic alloy, anomalous eutectic forms within the whole range of cooling rates. The increase of cooling rate has two obvious effects on both alloys: one is the microstruc- ture refinement, and the other is that it produces more crys- tal defects to intensify the scattering of free electrons, leading to a remarkable increase of electrical resistivity. Under the condition that the grain boundary reflection coefficient r approaches 1, the resistivity of rapidly solidified Co-Sn alloys can be predicted theoretically.展开更多
Droplets of Ag60Sb34Cu6 ternary alloy within the diameter range of 60—800 μm were rapidly solidified by means of drop tube containerless processing, and the solidi- fication mechanism is analyzed. With a decrease in...Droplets of Ag60Sb34Cu6 ternary alloy within the diameter range of 60—800 μm were rapidly solidified by means of drop tube containerless processing, and the solidi- fication mechanism is analyzed. With a decrease in droplet size, the cooling rate increases from 57 to 5.8×104 K/s. The maximum undercooling is determined to be 180 K (0.23TL) and the microstructure of primary ε(Ag3Sb) dendrite refines drastically until homogenous equiaxed dendrite forms. Ex- perimental results indicate that (ε+Ag) pseudobinary eutectic cannot form under high undercooling conditions and the solubility of Ag in primary ε phase increases as undercooling increases. Based on thermal analysis and crystal growth morphology, it is found that this alloy is solidified in two ways corresponding to different undercooling levels.展开更多
文摘The rapid solidification behavior of Co-Sn al- loys was investigated by melt spinning method. The growth morphology of αCo phase in Co-20%Sn hypoeutectic alloy changes sensitively with cooling rate. A layer of columnar αCo dendrite forms near the roller side at low cooling rates. This region becomes small and disappears as the cooling rate increases and a kind of very fine homogeneous microstruc- ture characterized by the distribution of equiaxed αCo den- drites in γCo3Sn matrix is subsequently produced. For Co-34.2%Sn eutectic alloy, anomalous eutectic forms within the whole range of cooling rates. The increase of cooling rate has two obvious effects on both alloys: one is the microstruc- ture refinement, and the other is that it produces more crys- tal defects to intensify the scattering of free electrons, leading to a remarkable increase of electrical resistivity. Under the condition that the grain boundary reflection coefficient r approaches 1, the resistivity of rapidly solidified Co-Sn alloys can be predicted theoretically.
文摘Droplets of Ag60Sb34Cu6 ternary alloy within the diameter range of 60—800 μm were rapidly solidified by means of drop tube containerless processing, and the solidi- fication mechanism is analyzed. With a decrease in droplet size, the cooling rate increases from 57 to 5.8×104 K/s. The maximum undercooling is determined to be 180 K (0.23TL) and the microstructure of primary ε(Ag3Sb) dendrite refines drastically until homogenous equiaxed dendrite forms. Ex- perimental results indicate that (ε+Ag) pseudobinary eutectic cannot form under high undercooling conditions and the solubility of Ag in primary ε phase increases as undercooling increases. Based on thermal analysis and crystal growth morphology, it is found that this alloy is solidified in two ways corresponding to different undercooling levels.
