Experimental Study on the Impact of Macrosegregation Formation of the Al-Bi Hypermonotectic Alloys

The solidification experiments about macrosegregation formation of the Al-10%Bi hyper monotectic alloys under gravity conditions have been carried out. The results showed that the average diameter of the Bi-rich droplets linearly increases and the number density of the Bi-rich droplets exponentially decreases with solidification time under the gravity condition. Because of gravity settling and collisions coagulation between the droplets, area fraction of Bi-rich increased rapidly in the bottom of samples during early solidification. It’s easy to form Bi-rich layer at the bottom of the sample. The analysis demonstrates that nucleation and diffusion growth of drops are the dominant factors influencing the solidification microstructure during the early solidification and the same distribution of Bi-rich in different locations of sample. As the solidification process, gravity migration and collision coagulation beginning to play the leading role, lead to the difference in the distribution of Bi-rich droplets in different locations of sample 90%e5%a2%9e%e5%a4%a7&tjType=sentence&style=&t=increases+gradually" increases gradually in the same time. It caused macrosegregation of the final solidification microstructure under the gravity condition.