The microstructure and hardness of Ni-Co-Al-Ti-Cr quinary alloys

K. A. Christofidou, Nicholas Jones, Ed Pickering, Roxana Flacau, Mark C Hardy, H. J. Stone

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    Abstract

    The effects of Ni:Co and Al:Ti ratios on the room temperature microstructure, hardness and lattice parameter of twenty-seven quinary Ni-Co-Al-Ti-Cr alloys have been evaluated. All of the alloys exhibited a uniform γ-γ′ microstructure. Differential scanning calorimetry (DSC) showed that the liquidus and solidus temperatures of the alloys increased with greater Al:Ti ratios, decreased with Cr concentration and remained largely unchanged with respect to the Ni:Co ratio. Neutron diffraction measurements of the γ and γ′ lattice parameters revealed that the lattice misfit in all of the alloys was positive and increased with Ti concentration (i.e. lower Al:Ti ratio) regardless of the concentration of Cr, or the ratio of Ni:Co. Importantly, alloys with a Ni:Co ratio of 1:1, were found to have consistently greater lattice misfits than alloys with Ni:Co ratios of either 1:3 or 3:1. The measured lattice misfits were found to be strongly correlated with the Vickers hardness of the alloys, suggesting that lattice misfit plays a key role in the strengthening of γ-γ′ alloys of this type.

    Original languageEnglish
    Pages (from-to)542-552
    Number of pages11
    JournalJournal of Alloys and Compounds
    Volume688
    Issue numberB
    Early online date18 Jul 2016
    DOIs
    Publication statusPublished - 15 Dec 2016

    Keywords

    • High-temperature alloys
    • Metallography
    • Metals and alloys
    • Microstructure
    • Neutron diffraction

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