Abstract: Nonstable growth of Al-Si eutectic in constrained condition has been investigated by means of change of the withdrawing rate in an unidirectional solidification system,In constant acceleration growth,a retarded effect of response of eutectic interflake spacing on the growth rate has been observed.The response mechanisms are cluster-branching and local termination extension of Si-phase.In constant deceleration growth,the cluster-branching and termina- tion mechanisms of silicon still control adjustment of the interflake spacing,but the spacing is determined by the initial growth rate and does not respond to the decreasing growth rate.

Key words: Al-Si eutectic, nonstable growth, Si-phase cluster-branching