MODELING THE EFFECTS OF HEAT TREATMENT ON MICRO-SEGREGATION IN ULTRAHIGH-STRENGTH CAST STEEL
Open Access
- Author:
- Paret, Kyle Edward
- Area of Honors:
- Industrial Engineering
- Degree:
- Bachelor of Science
- Document Type:
- Thesis
- Thesis Supervisors:
- Dr. Bob Voigt, Thesis Supervisor
Robert Carl Voigt, Thesis Supervisor
Dr. Paul M Griffin, Thesis Honors Advisor - Keywords:
- Diffusion Modeling
Micro-Segregation
UHS Cast Steel
Tungsten - Abstract:
- Ultrahigh-strength (UHS) cast steel alloys are used in a wide range of commercial and military applications. However, dendritic micro-segregation during solidification of cast steels can be detrimental to mechanical properties. This thesis presents the development and results of a theoretical diffusion model which investigates the effects of heat treatments (specifically homogenization) on dendritic micro-segregation in ultrahigh-strength cast steels. The applications of this model can help in determining, predicting, and understanding what is necessary in regard to heat treatment of cast steel alloys. Using this model, material scientists and metallurgists will be able to more easily determine the times and temperatures necessary for optimal diffusion conditions. Results show that current heat treatment processes for UHS cast steels are only fully effective in situations where the secondary dendrite arm spacing (DAS) is sufficiently small. Even after a full heat treatment cycle, significant levels of micro-segregation remain for substitutional alloying elements when the DAS is greater than 40 μm. Experimental results showed that in scenarios with large DAS (≥ 200 μm), complete diffusion of alloying elements was not feasible. Furthermore, the diffusion model suggests that current experimental homogenization times and temperatures are inadequate to fully diffuse tungsten atoms at DAS greater than 20 μm.