Description1.) Introduction/ Purpose:
Z-steels are a new promising generation of creep resistant martensitic Cr-steels which contain Tantalum for the formation of long-term stable precipitates CrTaN of type Z-phase. As the demand for simulating the microstructural stability and evolution of this new material rose in the past years, there was a strong need to create a new CALPHAD-type thermodynamic database including the relevant precipitate phases containing Tantalum.
A thermodynamic Z-steel database for the precipitation kinetic software MatCalc was developed by implementing Tantalum. Precipitate sizes, chemical compositions, binary/ ternary diagrams of investigated systems (such as Ta-C, Ta-N, Ta-C-N), diffusion data, atom solubilities and first principle calculations from literature were collected and used in the database creation. Additionally, DSC measurements were conducted to determine the dissolution temperature of Z-phase. In addition to thermodynamic equilibrium calculations of the system, it is now possible to model nucleation and transformation of fcc MX precipitates and of bcc M2X precipitates into Z-phase in MatCalc version 6 by applying the concept of equivalent interface energy and minimum nucleation radius.
The precipitation evolution during manufacturing and high-temperature aging of two sample alloys was modelled and compared to TEM, SEM and EBSD measurements. The results show good agreement between simulation and experiment.
The new thermodynamic database is able to model MX and M2X nucleation, their transformation into Ta-containing Z-phase and the coarsening phenomena during high-temperature aging.
|Period||4 Sept 2019|
|Event title||European Congress and Exhibition on Advanced Materials and Processes: EUROMAT 2019|
|Location||Stockholm, SwedenShow on map|
|Degree of Recognition||International|
- Precipitation Kinetics
FWF - Software Development - Software Development on Dislocation Creep in Alloys
Project: Research project