Thermodynamic aspects of grain refinement of Al–Si alloys using Ti and B

Abstract

A thermodynamic assessment of ternary Al–Si–Ti phases was performed. Published datasets for the other subsystems were checked and adapted. Based on that, a consistent thermodynamic description of quaternary Al–Si–Ti–B alloys was generated. This was applied in a calculation of Al–Si–Ti–B phase diagram sections for practically relevant temperatures and compositions of Al–Si alloys from Al-rich to typical Al–Si foundry alloys. These stable and metastable phase diagrams could be correlated to many detailed aspects of possible reactions observed or suggested in experimental studies of grain refining. Understanding the mechanisms of grain refining of Al wrought alloys and Al–Si foundry alloys using titanium and boron requires a fundamental knowledge of both thermodynamic and kinetic aspects of this complex process. This work focuses exclusively on the thermodynamic aspects and the phase diagrams, which were not available for the quaternary alloys and partly incomplete and inconsistent for the ternary subsystems.