Interlamellar spacing in Al-Si eutectic growth controlled by temperature gradient

According to irregular eutectic growth model two characteristic parameters are differentiated within revealed morphology: the first (lambda(i)) - adequate to the formation of lamellar structure in steady-state and the second (lambda(s)(i)) - to extreme development of the perturbation due to marginal wavelength at non-faceted s/l interface. The selection of both above parameters among all the spacings revealed on cross-sections of the Al-Si eutectic alloy solidified directionally is also made. Some values of the lambda(i) and lambda(s)(i) parameters obtained by means of calculation made using the new growth law for the same values of growth rate v and temperature gradient G as those imposed during solidification of the Al-Si eutectic alloy are compared to the spacings selected within oriented morphology. An influence of temperature gradient G(G(x), G(z)) on lamellar structure formation during irregular eutectic growth is emphasized. The analysis is based on existence of two thermodynamic states: stationary state leading to formation of regular structure and rotation around stationary state leading to branching phenomenon due to instability at the s/l interface of non-faceted phase.