Dilatometric measurement techniques for the direct investigation of kinetics in structurally complex materials
Martin Luckabauer
Institute of Materials Phyics
12:00 - 12:20 Thursday 23 October 2014 Rechbauerstrasse 12, HSII Dilatometry is well-established for the characterization of materials behavior in response to thermal treatment. In such measurements the thermal expansion caused by the sum of all volume affecting processes in the specimen is recorded as a function of temperature. Processes like, e.g., first and second order phase transitions, shrinkage due to pore annihilation and thermal expansion caused by changes in the interatomic potential can be assessed. However, a major drawback of standard dilatometry arises from the fact that only the cumulated expansion or shrinkage is accessible. A separation of the different underlying physical processes requires refinement by additional measurement techniques.
In this talk two advanced dilatometric techniques for overcoming the above mentioned limitations are presented. The first technique is high-resolution isothermal -dilatometry based on differential laser-interferometry. With this technique a relative length change resolution of five ppm at measurement times of up to 14 days is achievable. As an example quantitative results obtained for the atomic vacancy kinetics in a B2-FeAl intermetallic compound are presented. The second technique aims at the continuous measurement of the short time response of a material by a periodic modulating of the measurement temperature or the heating rate. With this technique the unambiguous separation of different volume affecting processes is possible. Obtained results for the low temperature crystallization kinetics of a bulk metallic glass are presented and discussed with respect to the limitations of the method.
| 