METTRANS-ISS FP - Metastable Solidification of Novel Peritectic Structures - Studies With Transparent Model Alloys: ISS Flight Preparation

Many commercial metals such as steels, bronze and various copper alloys show a peritectic reaction during solidification, meaning that the solid forming during freezing of the melt suddenly changes from an alpha- to a beta-type crystal. Although economically of great importance this phenomenon is still little understood, especially when it comes to optimization of product quality by microstructure adjustment. Detailed investigations on Earth are disturbed by natural convection, which is always present during cooling of a melt.

The METCOMP team from the European Space Agency (ESA) thus intends to perform specific microgravity experiments on sounding rockets and on the International Space Station (ISS) where natural convection is mostly suppressed.

One of these experiments will use a transparent analogue material which solidifies like a metallic alloy but allows the observation of the solidification dynamics and phenomena occurring at the solid/liquid interface. This material will be processed on the ISS within the TRANSPARENT ALLOYS instrument developed by ESA. This instrument will serve as a highly specified tool for long-term investigations on transparent model materials under reduced gravity conditions on the ISS. Presently ground based laboratory investigations are in progress in order to calibrate the new instrument and thus define the process window for the upcoming experiments on ISS.

Various peritectic growth modes have already been identified, such as two-phase array growth of alpha and beta cells/dendrites, second-phase nucleation ahead of the primary front and subsequent island growth or formation of lateral layered structures and the celebrated isothermal couple peritectic growth. The quantitative determination of the corresponding process window for all these phenomena is ongoing.

The main partners of the associated ESA MAP (Microgravity Application Programme) project METCOMP are:

• Matthias Kolbe, German Aerospace Center (DLR), Germany
• Michel Rappaz, École Polytechnique Fédérale de Lausanne (EPFL), Switzerland

Coordinator

Montanuniversität Leoben, Chair for Simulation and Modelling of Metallurgical Processes - Andreas Ludwig

Montanuniversität Leoben - Chair for Simulation and Modelling of Metallurgical
Andreas Ludwig
Franz-Josef-Straße 18
A-8700 Leoben
Tel.: +43 (3842) 402 - 3101
E-mail: smmp@unileoben.ac.at