Feedback control of unstable cellular solidification fronts

TL;DR

This study demonstrates how feedback control using real-time imaging and local heating can stabilize and regularize cellular solidification patterns in directional solidification of alloys, both numerically and experimentally.

Contribution

It introduces a novel feedback control method combining real-time image processing and laser heating to stabilize cellular patterns in solidification.

Findings

Cellular arrays can be stabilized below the period-doubling threshold.

Feedback control leads to uniform cellular spacing.

Minimal heating is sufficient for stable pattern control.

Abstract

We present a numerical and experimental study of feedback control of unstable cellular patterns in directional solidification (DS). The sample, a dilute binary alloy, solidifies in a 2D geometry under a control scheme which applies local heating close to the cell tips which protrude ahead of the other. For the experiments, we use a real-time image processing algorithm to track cell tips, coupled with a movable laser spot array device, to heat locally. We show, numerically and experimentally, that spacings well below the threshold for a period-doubling instability can be stabilized. As predicted by the numerical calculations, cellular arrays become stable, and the spacing becomes uniform through feedback control which is maintained with minimal heating.