Papers by Keyword: D-Electrons Concept

Abstract: To theoretically evaluate three widely used second generation single crystal superalloys-PWA1484, ReneN5 and DD6, the alloy densities, phase graphs, TCP contents, d-electron energy, and creep rupture lives were calculated, and the calculation results were analyzed combined with actual data. Results showed that among the three alloys, PWA1484 had the greatest density, secondly was DD6, and ReneN5’s density was the lowest. The PWA1484 alloy was most likely to precipitate TCP due to its highest d-orbital energy level; the ReneN5 alloy had a medium d-orbital energy level, but its high Cr content induced it to precipitate the most TCP types; the DD6 alloy had the least chance to precipitate TCP phases because of its lowest d-orbital energy level as well as lowest Cr content. It is concluded that thermodynamic calculation had the ability to simulate TCP types and TCP content at steady states, while d-orbital energy concept was capable of exhibiting the alloys in sequence of TCP precipitation potential. Mere thermodynamic calculation will lead to comparatively conservative results, including more TCP types, higher TCP contents and lower rupture lives. Analyzing the thermodynamic and d-orbital energy calculations comprehensively, it can be considered that the DD6 alloy has the most stable microstructure among the three single crystal superalloys.

Abstract: A molecular orbital approach to alloy design has recently made great progress. Single crystal Ni-based superalloys and high Cr ferritic steels have been developed following this approach. Some perspectives will also be described on the design of heat resistant alloys.

Abstract: A molecular orbital approach to alloy design has recently made great progress. This approach is based on the electronic structure calculations by the DV-Xα molecular orbital method. New PHACOMP and the d-electrons concept have been constructed and applied to alloy design. Recently, nickel-based single crystal superalloys for power generation gas turbine blades and high Cr ferritic steels for turbine rotors have been developed successfully with this approach.