Recrystallization Response during Thermo‐Mechanical Processing of Alloy René 65 Billet

Minisandram, Ramesh S.; Jackman, L.A.; Russell, Jeffrey L.; Lasonde, Michael L.; Heaney, Joseph A.; Powell, Andrew M.

doi:10.1002/9781119016854.ch8

Cited by 6 publications

(2 citation statements)

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“…The material used in the present study is the γ/γ′ nickel based superalloy René 65, which has recently been developed by ATI Allvac and General Electric [15][16][17][18] . The austenitic FCC γ matrix is strengthened by a high volume fraction (~40%) of γ′ particles [LI 2 structure, Ni 3 (Al,Ti)].…”

Section: Materials and Surface Anomaliesmentioning

confidence: 99%

Assessment of specific contribution of residual stress generated near surface anomalies in the high temperature fatigue life of a René 65 superalloy

Gourdin

Cormier

Gardin

et al. 2016

Fatigue Fract Eng Mat Struct

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This study evaluates the influence of residual stresses induced by the fabrication of surface anomalies on the fatigue crack growth in a nickel based superalloy. To separate the notch effect of the geometry from the residual stress field induced by fabrication of the surface flaws, two V‐type anomalies are considered: scratches and dents with equivalent morphology and size. A specially designed heat treatment has been used to reduce the magnitude of residual stresses around these anomalies in order to highlight their effects on the different stages of the crack propagation, under low cycle fatigue conditions at 400 °C. The crack initiation life is short for both anomalies but in the presence of compressive residual stresses, a decrease of the fatigue crack growth rate has been observed during the first stages of the crack propagation. Furthermore, the results showed that without residual stresses, scratches and dents exhibit the same behaviour. Thus, the residual stress field below surface anomalies is the main parameter controlling the fatigue life from surface anomalies.

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Section: Materials and Surface Anomaliesmentioning

confidence: 99%

Assessment of specific contribution of residual stress generated near surface anomalies in the high temperature fatigue life of a René 65 superalloy

Gourdin

Cormier

Gardin

et al. 2016

Fatigue Fract Eng Mat Struct

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“…The AD730 TM nickel-based superalloy whose composition is Ni-15.7Cr-8.5Co-4.0Fe-3.4Ti-3.1Mo-2.7W-2.25Al-1.1Nb-0.01B-0.015C-0.03Zr (wt.%) [17] is studied. Samples are cut out from an AD730 TM billet which contains elongated unrecrystallized grains typical of many cast-and-wrought heavily-alloyed γ/γ' nickel-based superalloys [18][19][20]. These grains are inherited from the ingot conversion process and characterized by a high density of intragranular precipitates.…”

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confidence: 99%

γ′ precipitates with a twin orientation relationship to their hosting grain in a γ-γ′ nickel-based superalloy

Vernier

Franchet

Dumont³

et al. 2018

Scripta Materialia

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In a polycrystalline γ-γ' nickel-based superalloy, γ' precipitates with a close-to-twin orientation relationship to their surrounding matrix (named T-type precipitates) are found in recrystallized grains located near specific unrecrystallized grains (named recovered grains). This type of γ/γ' interface has not been reported in literature before. Inherited from the ingot conversion process, recovered grains are characterized by a high density of micrometric and close-to-coherent γ' precipitates. Resulting from the interaction of the recrystallization front with the latter precipitates, the T-type precipitates appear to form onto the recrystallization front. The present paper details the crystallographic characteristics of the T-type precipitates. KeywordsGamma -Gamma Prime nickel-based superalloy, Interphase boundary, Twin boundary, Recrystallization.Polycrystalline γ-γ' nickel-based superalloys are commonly used to manufacture aircraft engine rotative parts due to their good mechanical behavior at high temperature (tensile, fatigue, creep resistance) [1]. Parts are usually derived from cast ingots through forging sequences [2,3]. They are made of a γ matrix in which γ' precipitates of various sizes are distributed. Both γ and γ' phases have a cubic structure but, while the γ phase is a Face Centered Cubic (FCC) non-ordered solid solution, the γ'-Ni 3 (Al,Ti) phase has a L1 2 ordered structure. Yet, the mechanical properties of the alloy do not only depend on the size and spatial distribution of the precipitates [4], but also on the γ/γ' interface characteristics [5,6]. Indeed, γ' precipitates are reported in literature as coherent, semi-coherent or incoherent to their surrounding matrix [7]. Coherency means that the γ and γ' crystal lattices perfectly coincide at the γ/γ' interface. This is made possible by a low lattice parameter mismatch between the γ and γ' phases [8]. Coherent γ/γ' interfaces have very low energies [9,10] and form during the cooling stages of the forging process for example. However, if some misfit dislocations pile up at the γ/γ' interface, the lattice matching is only partial and the interface is semi-coherent [7]. Semi-coherency occurs when external stresses (high temperature plastic deformation) or internal stresses (e.g. induced by long aging treatments leading to particle coarsening) generate dislocation loops which are incorporated into the γ/γ' interface as misfit dislocations [11]. Finally, when there is no crystal lattice matching, the γ/γ' interface is incoherent and has a high energy [9]. Secondary γ' precipitates which form during the cooling stages of the forming process, are coherent with a cube-cube orientation relationship: they evolve from spheres to {100} bounded cubes as their size and/or the lattice misfit increase [12]. On the other hand, primary γ' precipitates, derived from the as-cast microstructure and high temperature billet forging sequences, are usually incoherent with no special orientation relationship, excepted in case of heteroepitaxial recrystallizat...

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The Effect of Microstructure on the Strength of VDM Alloy 780

Hardy

Haghighat²,

Argyrakis

et al. 2023

The Minerals, Metals &Amp; Materials Series

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Recrystallization Response during Thermo‐Mechanical Processing of Alloy René 65 Billet

Cited by 6 publications

References 0 publications

Assessment of specific contribution of residual stress generated near surface anomalies in the high temperature fatigue life of a René 65 superalloy

Assessment of specific contribution of residual stress generated near surface anomalies in the high temperature fatigue life of a René 65 superalloy

γ′ precipitates with a twin orientation relationship to their hosting grain in a γ-γ′ nickel-based superalloy

The Effect of Microstructure on the Strength of VDM Alloy 780

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