Solidification path, high temperature phase equilibria and the effect of solidification parameters on microstructure during directional solidification of TiAl based alloys
Development of new TiAl based alloys requires experimental data about their high temperature phase equilibria, phase transformation temperatures and solidification path to verify validity of thermodynamic calculations used for their design. Directional solidification in a Bridgman type apparatus combined with quenching and in situ measurements of temperature profiles is applied for such fundamental experimental studies. Microstructure analysis of quench during solidification samples and in-situ temperature measurements result in identification of primary solidification phase, solidification path and estimation of phase transformation temperatures.
- To redesign the Bridgman type apparatus for in-situ measurements of temperature profiles within the samples during directional solidification.
- To study the effect of solidification parameters on morphology of solid-liquid interface and microstructure of TiAl based alloys using quench during solidification experiments
- To determine primary solidification phase and solidification path using quenching during directional solidification (QDS) experiments.
- To determine primary solidification phase and describe microstructure evolution within the mushy zone and directionally solidified part of samples.
- The Bridgman type apparatus was redesigned for in-situ measurements of temperature profiles within the samples during directional solidification and measurements static and dynamic temperature gradients.
- Quenching during directional solidification experiments allowed to preserve morphology of solid-liquid interface as a function of applied growth rate and temperature gradients. At the applied solidification parameters, the solid-liquid interface change from cellular to dendritic one.
- The primary solidification phase and solidification was determined for TiAl based with various content of oxygen.
- In situ temperature measurements of temperatures in the samples during heating and cooling allowed to estimate phase transformation temperatures during solidification and solid phase transformations.
- The dependence of primary dendrite arm spacing on applied growth rate and temperature gradient in liquid was experimentally determined.
OM micrographs showing the effect of growth rate V on morphology of solid-liquid interface at a constant temperature gradient
Example of heating curve measured in situ in the sample using Bridgman apparatus for directional solidification
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