A new system has been developed for in situ obsevation of phase transformation at high temperatures. Changes in powder diffraction patterns from a heated specimen can be measured continuously by scanning an image plate located behind a slit. A heating system is designed for a sheet specimen (ca. 5×6 mm2) using Joule-heating, and it can heat the specimen up to 1100K at a rate up to 160K/sec, where effects of thermal expansion are minimized by a mechanism releasing stress.
This system was applied to Zn-coated steel. At temperatures higher than the melting point of Zn, different types of Fe-Zn intermetallics formed sequentially through rapid inter-diffusion. Changes in phase and crystallographic structure were monitored with a time resolution less than a few seconds. It has been found that an addition of a small amount of elements, such as P, into Fe changes an incubation time before the alloying reaction starts. This system has been shown to have the potential for application to in situ observation of other reactions at high temperatures.
