Ultrahigh speed imaging system for the measurement of solidification velocity via direct observation of rapid solidification

Abstract

An ultrahigh speed imaging system has been developed and built to image rapid solidification of materials. The system collects data from a 10 by 10 array of parallel tapped photodiodes. Up to 8192, frames of data are digitized with 8-bit flash converters at frame rates ranging from 500 to 1 000 000 frames per second. The system has been used to image solidification of a gamma titanium aluminum (γ-TiAl) alloy, with composition Ti-60a/o Al, over a range of undercoolings. The data collected includes the first images of solidification from multiple solidification fronts, images of solidification of a disordered phase followed by the alloy ordering, and quantitative measurement of solidification velocity as a function of undercooling in a γ-TiAl alloy.