Concentric Solidification for High Temperature Laser Scanning Confocal Microscopy

Abstract

A new experimental technique defined as concentric solidification has been developed to improve in-situ observations of solidification and high temperature phase transformations using laser scanning confocal microscopy (LSCM). The technique consists of applying a radial thermal gradient across a 10 mm diameter sample such that the maximum temperature is focused in the centre of the specimen. Careful control over the sample thickness, heating rate and peak temperature results in the formation of a liquid pool in the centre of the specimen. Surface tension balance between solid, liquid, gas and crucible result in minimal meniscus formation on the liquid pool, leading to a greatly enhanced in-situ observations. Examples of the range of observations possible as well as unique observations of segregation related phenomena are presented.

Enhanced Concentric Solidification Technique for High-Temperature Laser-Scanning Confocal Microscopy

“…In 2004 an advanced experimental technique for hightemperature laser-scanning confocal microscopy (HTLSCM) has been developed by Reid et al, 1) which has been further developed and utilized for the experiments conducted in the present study. The details of HTLSCM have been described in detail in the literature 1) and there is no need to repeat these details.…”

"In-situ" Observation of the .DELTA./.GAMMA. Phase Transformation on the Surface of Low Carbon Steel Containing Phosphorus at Various Cooling Rates

“…However, the Confocal Scanning Laser Microscope (CSLM) has recently provided the convenient possibility of making an "in-situ" observation of the phase transformation on the surface of samples at high temperature. Reid 8) recently reviewed the development history of CSLM and made a detailed description of the advantages and limitations of CSLM by comparing it with other established techniques to study the microstructural development at high temperatures, such as X-ray transmission experimental techniques, directional solidification studies, optical and electron microscopy, high temperature transmission electron microscopy and thermionic transmission microscopy. A more enhanced understanding of the solid state phase transformation is being anticipated by the CSLM.…”

High‐temperature laser‐scanning confocal microscopy as a tool to study the interface instability during unsteady‐state solidification of low‐carbon steel

“…In this study, we used a LSCM system and the so-called 'concentric solidification' technique, developed and described by Reid et al (2004) to improve the quality of real-time observations of solidification in a high-temperature laserscanning confocal microscope at varying cooling rates and thickness of sample. The laser-scanning confocal microscope used in this study was made by Lasertec Corporation, based on Yokohama, Japan.…”

“…Unlike the Bridgman-type furnace, the LSCM apparatus provides the possibility of in situ observations of the progress of solidification as well as the subsequent solid-state phase Reid et al (2004) transformations at temperatures as high as 1873K. A drawback of the conventional LSCM system is that the temperature gradient in the liquid at the solid/liquid interface cannot be controlled.…”