Mechanical Properties of Nb<SUB>3</SUB>Al-Base Intermetallics Prepared by a Ceramic Mold-HIP Process

Abstract

The Nb 3 Al-type intermetallic is expected as a candidate for high-temperature structural materials because of its high melting point and relatively lower density, though poor in plastic workability at room temperature. Here the Ceramic Mold-HIP process was employed to fabricate the NNS compacts of brittle Nb 3 Al intermetallic and Nb 3 Al-base composites. Complex-shape compacts such as blades and pyramids were fabricated without any cracks by adjusting the chemical composition of the Nb 3 Al-base alloy to have high compressive fracture strength at room temperature. High-temperature strength in the range of 1873 to 2073 K was evaluated by compressive and tensile tests. The maximum compressive strength at 2073 K was 151.4 MPa for Nb-20 at%Al-26 at%Mo alloy, while the corresponding maximum tensile strength was only 12.9 MPa for the Nb-19.3 at%Al-44.8 at%Mo alloy. The strain rate sensitivity of compressive stress at high temperatures was also evaluated using the strain rate conversion method. Further, the 5.7% tensile elongation at room temperature was achieved by Nb-25 at%-35 at%Mo plus Nb foil composite, even though the Nb 3 Al-base alloy itself is brittle at room temperature.