Lamella-rod pattern transition and confinement effects during eutectic growth

We present an in situ experimental study of the lamellar-to-rod transition during directional solidification a model eutectic transparent alloy –the succinonitrile-(d)camphor (SCN-DC) system. Coupled-growth patterns, and their morphological transformations upon changes pulling velocity V (3.5?70.0nms?1) were observed real time series flat-wall samples with different thicknesses ? from 15 (thin samples) to 350 µm (thick samples). At relatively large velocity, rod-like patterns formed systematically. In contrast, stable lamellae at sufficiently low regardless sample thickness investigated range. confined-geometry (?=30?140 µm), lamellar over range interphase spacing ? V. The lamella contact walls stabilized against propagative breakup, formation rods was mediated by secondary instabilities such as zigzag mode spatial-oscillation mode. bistable range, hysteresis increasing or decreasing observed, well complex phenomena involving oscillatory, mixed hybrid patterns. (reverse) involved rod elongation instability. A discussion on elementary mechanisms that determine lamellar-rod transition, dependence is initiated.