Abstract
The alloy Ni−20 at. % Mo is FCC and disordered at high temperatures, but below 868°C forms a superlattice of the D1a type. The disordered structure can be retained by quenching, and subsequent aging below 868°C can develop a variety of ordered domain structures. In the disordered condition, the yield stength at 25°C is typically 140– The tensile properties were measured for two ordered domain sizes: 24 nm and 3,000 nm. For the 24 nm domain size, the yield strength at 25°C was 862 MPa (125,000 psi). This decreased with increasing test temperature to about 690 MPa (100,000 psi) at 800°C, then decreased greatly to about 210 MPa (30,000 psi) at 1000°C. In the ordered condition, the alloy had a very low ductility (1% elongation or less) from 25°C to the disordering temperature of 868°C, above which it increased considerably (e.g., 30% elongation). The alloy with the 3,000 nm domain size showed similar behavior, although the strength was less. (The ordered alloy with 24 nm domain size had a yield strength-temperature curve similar to that of Waspaloy.) These results are correlated with fractography of the tensile samples.
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Kao, H.P., Brooks, C.R. & Vasudevan, K. High Temperature Strength of Ordered and Disordered Ni4Mo. MRS Online Proceedings Library 81, 335–340 (1986). https://doi.org/10.1557/PROC-81-335
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DOI: https://doi.org/10.1557/PROC-81-335