Microstructure and Properties of Composites Prepared by Reactive Pressure Infiltration of Aluminium into Metal and Ceramic Powder Preforms

Nickel aluminides exhibit very attractive high temperature properties. However, due to high melting temperatures they are difficult to prepare. Gas pressure reactive infiltration is a relatively cheap technology that provides composites where nickel aluminides are formed due to mutual reaction between Ni powder and molten aluminium forced to penetrate into powder preform. The feasibility of this concept is demonstrated in this work. Ni powder and/or Ni+25 vol. % Al2O3 powder mixture, respectively, were mechanically pressed and then infiltrated with aluminium using 5 MPa argon gas pressure at the temperature of 750 degrees C for 120 s. Al/Al2O3 composite using loose alumina powder was prepared in similar manner for comparison. The microstructure of composites was observed by scanning electron microscopy and newly formed intermetallic phases were analysed by energy-dispersive X-ray spectroscopy. Relative elongations during additional thermal cycling up to 800 degrees C had been recorded. Composites were additionally characterized by hardness measurements.