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Influence of transition group elements on the stability of the delta- and eta-phase in nickelbase alloys

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Original languageEnglish
Article number015005
Number of pages15
JournalModelling and simulation in materials science and engineering
Volume26
Issue number1
DOIs
Publication statusPublished - 7 Dec 2017

Abstract

To improve the high-temperature capability of 718-type wrought nickel-base superalloys, the gamma'-phase (Ni3Al) can be stabilized. However, this also reduces the size of the forging window because forging has to be done above the grand below the solvus temperature of the phase that is used to enable fine-grain forging, i.e. the delta-phase of Ni3Nb type or the eta-phase of Ni3Ti-type. Understanding the influence of alloying elements on the formation of these phases is therefore important. In this paper, density functional theory calculations at 0 K are performed to determine the stabilizing effect of aluminium and of the transition group elements on the stability of the delta-phase and eta-phase. Most of the transition group elements of 5th and 6th period stabilize the delta-phase, whereas the stabilizing effect on the eta-phase is weaker. According to the calculations, Mo, Tc, W, Re, and Os may be expected to stabilize the delta-phase but not the. eta-phase, whereas Al and Zn strongly stabilize the eta-phase. V, Zr, Ru, Rh, Pd, Ag, Cd, Hf, Ta, Ir, Pt, Au, and Hg stabilize both phases. For some elements (Cr, Mn, Fe, Co), magnetic effects in the d and especially in the.-phase are shown to be significant at the concentrations studied here.

    Research areas

  • density functional theory, nickelbase superalloys, phase stability, nickel alloys, TOTAL-ENERGY CALCULATIONS, AUGMENTED-WAVE METHOD, BASIS-SET, INITIO, SUPERALLOYS

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