טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentShaul Avraham
SubjectReactive Wetting and Characterization of i-3A Materials
DepartmentDepartment of Materials Science and Engineering
Supervisor Full Professor Kaplan Wayne D.


Abstract

Metal-ceramic composites are attractive candidates for a wide range of applications. This is due to their improved mechanical properties compared to the properties of monolithic materials. Aluminide intermetallics have a relatively high melting temperature (Tm>1300°C) and low densities, which explains their potential application as a high temperature structural materiel. The aluminide is formed by a reaction between a reactive oxide and aluminium.


A relatively new processing method was applied; the infiltrated Al2O3-Al3X alloy (i-3A) technique. The process is based on pressure infiltration of Al into a porous ceramic preform that contains a-Al2O3 and TiO2. Infiltration is governed by the wetting behavior of the liquid. The i-3A process temperature is relatively low (600-800ºC) and the processing time is rather short (>1 min).


The ceramic matrix composites (CMC) produced and studied in this work are based on a-Al2O3-(Al-Si)3Ti interpenetrating networks. The formation of (Al-Si)3Ti is governed by the consumption of the intermediate phases (TiO and g-Al2O3) that are formed during the reduction of TiO2 by Al. The reaction results in intense heat that motivates TiO2 and Al2O3 phase transformations. Annealing of the sample results in the increased formation of a-Al2O3 followed by the formation of (Al-Si)3Ti. The high contact angle of Al on TiO2 and a-Al2O3 explains the fact that pressure infiltration methods were required. A fully reacted CMC was achieved after thermal annealing.