Processing and Mechanical Properties of Pressureless‐Sintered Niobium‐Alumina‐Matrix Composites

Abstract

Niobium-alumina (Nb-Al 2 O 3 ) composites have been fabricated via the pressureless sintering of compacts of intensively milled Nb-Al 2 O 3 mixtures. Strength and fracture toughness of the composites increase as the niobium content increases. For a composite that contains 50 vol% niobium, strengths of up to 680 MPa, with a corresponding fracture toughness of 6.3 ± 0.3 MPaؒm 1/2 and hardness of 6.4 GPa, have been obtained.

Microstructure of Alumina Composites Containing Niobium and Niobium Aluminides

“…Further details of the processing technique are reported elsewhere. 4,14 The densities of composite C1 and C0 were ϳ98% and ϳ95% of the theoretical density, respectively (Table I) …”

Reactive Processing in Ceramic‐Based Systems

“…Often, the ceramic phase has a significantly different thermal expansion coefficient than the metal phase, resulting in the development of stresses during thermal cycling. The Al 2 O 3 –Nb system is interesting because of the near match in the coefficient between the ceramic and metal phases 69,70 . Presumably, the thermal expansion match should minimize the residual stresses and allow for improved performance in applications requiring thermal cycling, if the interfacial adhesion is sufficient.…”

“…The Al 2 O 3 -Nb system is interesting because of the near match in the coefficient between the ceramic and metal phases. 69,70 Presumably, the thermal expansion match should minimize the residual stresses and allow for improved performance in applications requiring thermal cycling, if the interfacial adhesion is sufficient. Alumina-Nb composites can be formed by RHP using the following reaction: 71 10 Al þ 3…”

Wet Milling of Fe/Al/Al2O3and Fe2O3/Al/Al2O3Powder Mixtures

“…It was found that reaction sintering can also be used to manufacture highly dense Fe/Al 2 O 3 , Cr/Al 2 O 3 , or Nb/Al 2 O 3 cermets. 4,[7][8][9] These intermetallic or metal-reinforced alumina composites exhibit several advantages compared to single-phase ceramic materials, such as high strength, good wear resistance, improved fracture toughness, and tailorable electrical properties. The precursor powder mixtures for 3A-materials contain metal oxides (e.g., ZrO 2 , Fe 2 O 3 , TiO 2 , Nb 2 O 5 ), Al, and Al 2 O 3 or elemental metals (e.g., Fe, Nb), Al, and Al 2 O 3 .…”