Midway Evaluation in Physics - Máni Mehdi Maghsoudi

Title of thesis:
Mapping binary and ternary phase diagrams using laser-induced breakdown spectroscopy of liquid metal

Student:
Máni Mehdi Maghsoudi

Doctoral committee:
Dr. Kristján Leósson, Ph.D., Chief Scientific Officer, DTE ehf. Dr. Guðrún Arnbjörg Sævarsdóttir, Professor of Engineering at Reykjavik University
Dr. Georges Salloum-Abou-Jaoude, Senior Innovation Engineer, Constellium C-TEC, France
Dr. Snorri Þ. Ingvarsson, Professor of Physics, Faculty of Physical Sciences, University of Iceland

Abstract:
Laser-Induced Breakdown Spectroscopy (LIBS) is a rapid and versatile analytical technique used for both qualitative and quantitative analysis of elemental compositions in liquid aluminum alloys. This study employs LIBS to investigate the behavior of aluminum alloys in their liquid state and to create binary and ternary phase diagrams for Al-Zr and Al-Ti alloys. The investigation of Al-Mg alloys using LIBS shows that the signal intensity of magnesium increases exponentially with temperature, which aligns well with the observed changes in magnesium vapor pressure across the studied temperature range. A model is proposed to calculate the impact of the magnesium vapor phase on the LIBS signal intensity of Al-Mg alloys, and this model may also apply to other volatile species. Additionally, the study assesses the dissolution of manganese in liquid aluminum, comparing the results to existing dissolution models. It also explores the formation kinetics of TiB2 in the aluminum melt, indicating that the observed decrease in dissolved titanium over time corresponds with the formation of TiB2 around aluminum borides. Finally, the research includes a study of Al-Zr and Al-Ti binary and ternary alloys with varying concentrations of alloying elements using LIBS. The liquidus lines in the corresponding phase diagrams are mapped, and cooling rate studies demonstrate that Al-Zr alloys, in comparison to Al-Ti alloys with the same weight percentages, achieve a greater degree of undercooling before the nucleation of the Al3Zr phase begins.