טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentZamir Shlomit
SubjectSynthesis of Dense Light Weight Al3Ti/B4C Composites
by Pressure Assisted Thermal Explosion
DepartmentDepartment of Materials Science and Engineering
Supervisors Dr. Gotman Irena
Professor Gutmanas Elazar


Abstract

Al3Ti/B4C composites have a potential for light-weight armor applications due to the high hardness and strength-to-weight ratio of the titanium aluminide. Self-propagating High-temperature Synthesis (SHS) utilizing the exothermic heat of the 3Al+Ti à Al3Ti reaction could become an attractive route of in situ processing of such composites.

In the present research, dense Al3Ti/B4C composites containing up to 60 vol. % B4C were synthesized from a fine attrition milled Ti-3Al powder blend diluted with a coarse B4C powder. A recently developed method of pressure-assisted thermal explosion - Reactive Forging was employed. Green Ti-Al-B4C compacts were placed between preheated press rams and thermal explosion (SHS) was ignited at ram temperatures as low as 8000C. The temperature of the samples in the course of combustion synthesis was accurately monitored. The application of a relatively low pressure during thermal explosion resulted in densification of thus synthesized Al3Ti/B4C composites.

The activation energy of the 3Al+Ti àAl3Ti SHS reaction was calculated based on combustion wave velocity measurement and on temperature evolution curves obtained during thermal explosion. The significantly lower activation energy obtained for attrition milled reagent blends suggests that SHS process is strongly affected by mechanical activation.

The microstructure of the samples obtained was characterized by x-ray diffraction and scanning electron microscopy with chemical analysis (SEM/EDS). Due to the very short SHS processing time (less than 1 min), no undesirable reaction products were formed at the B4C particles/Al3Ti matrix interface.


The result of the present research suggest that SHS-based Confined Reactive Forging method can be used for the processing  of dense near-net-shape composites with large fractions of ceramic reinforcement.










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