ABSTRACT
Solidification processing is one of the important routes to produce materials, especially metals and alloys. The parameters for the transformation from liquid to solid, such as the temperature gradient, the growth rate, the cooling rate, the interphase velocity, vary from process to process and in one process also as a function of time and space. These variations together with the different alloy compositions, lead to a multitude of microstructures and therefore, affect the behavior of the material.
In this work the evolution of the interphases is studied in Sn-Zn (Sn-6wt.% Zn (hypoeutectic) and Sn-15wt.% Zn (hypereutectic)) when the specimens were unidirectionally horizontally solidified through heat extraction in two opposite directions. Sn-Zn specimens shaped in cylindrical segments were obtained, with an average length between 13 cm-17 cm, an average width between 3 cm-3.2 cm and an average thickness of 0.8 cm – 1.2 cm, depending on the experience.
The thermal parameters (cooling rates, temperature gradients, positions and velocities of the present interfaces) were determined and related to the final structures resulting from the solidification. It was found that the value of the velocity of the interphase is maximum when opposing fronts of solidification collide, advancing in opposite directions in the specimens. The values were superior to 2 mm/s for both analyzed Sn-Zn alloys.
Keywords
tin-zinc alloys; directional solidification; thermal parameters
