A nickel based superalloy has been designed where the fcc γ Ni matrix is reinforced by two different ordered-fcc intermetallic compounds, γ L1 2 Ni 3 Al and γ D0 22 Ni 3 V. Primary ageing at 900 − 1000 • C precipitated spherical L1 2 Ni 3 Al, whose volume fraction and size were controlled by altering the ageing temperature and time. Secondary ageing at 700 • C for 1 − 1000 h precipitated D0 22 Ni 3 V laths. The duplex precipitation increased hardness by up to 85 HV, with ∼ 500 MPa compressive proof strength maintained at 800 • C. Electron microscopy studied the Ni 3 Al precipitation and confirmed the form of the secondary Ni 3 V precipitates and their long term stability.Nickel based superalloys are widely used due to their combination of strength, creep, toughness, environmental resistance and microstructural stability in the 650 − 1200 • C interval [1,2]. Such alloys exploit the two-phase field that exists within the Ni-Al binary system to produce microstructures comprising a γ face-centred cubic (fcc) A1 (Strukturbericht designation) matrix, Figure 1a, 5 reinforced with γ L1 2 Ni 3 Al ordered-fcc intermetallic precipitates, Figure 1b. A variety of additional phases are used in multicomponent (∼ 10) commercial superalloys, including other intermetallics as well as carbides and borides. However, there is an additional ordered-fcc D0 22 γ phase, Figure 1c, that can be exploited in superalloys, e.g. Inconel 718 [3], which is also being explored in 10 other alloy systems [4,5,6]. Unfortunately, the D0 22 Ni 3 Nb phase in Inconel 718 is metastable [7,8] decomposing into the δ Ni 3 Nb D0 a orthorhombic P mmn phase [9, 10]. The Ni 3 X type intermetallics adopt a number of stable crystal structures as the X element is changed due to differing formation energies. For Ni 3 X intermetallics with X = Nb, Ta, Mo the stable structure is D0 a , while for 15 X = Ti the D0 24 structure is adopted, and with X = Al and Si the traditional γ * Corresponding

A correlative approach is employed to simultaneously assess structure and chemistry of (carbide and boride) precipitates in a set of novel Co/Ni-base superalloys. Structure is derived from electron backscatter diffraction (EBSD) with pattern template matching, and chemistry obtained with energy dispersive X-ray spectroscopy (EDS). It is found that the principal carbide in these alloys is Mo and W rich with the M6C structure. An M2B boride also exhibiting Mo and W segregation is observed at B levels above approximately 0.085 at. pct. These phases are challenging to distinguish in an SEM with chemical information (EDS or backscatter Z-contrast) alone, without the structural information provided by EBSD. Only correlative chemical and structural fingerprinting is necessary and sufficient to fully define a phase. The identified phases are dissimilar to those predicted using ThermoCalc. We additionally perform an assessment of the grain boundary serratability in these alloys, and observe that significant amplitude is only obtained in the absence of pinning intergranular precipitates.