Superplasticity in NiAl and NiAl-based alloys

Guo, Jingdong; Du, Xuanyu; Zhou, Lanzhang; Zhou, Bide; Qi, Yanxing; Li, G. G.

doi:10.1557/jmr.2002.0344

Cited by 8 publications

(5 citation statements)

References 18 publications

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“…It is found that the elongation at each deformation temperature increases with decreasing the strain rate. This strain rate dependence of elongation in the present alloy is similar to that of monolithic NiAl alloy [19]. The maximum elongation, 160%, is obtained at 1323 K and initial strain rate of 5.2 × 10 −4 s −1 under the deformation conditions studied in the present study.…”

Section: Constitutive Equationsupporting

confidence: 82%

High tensile elongation of a directionally solidified NiAl multiphase alloy at high temperatures

Cui

Jianting

et al. 2005

Materials Science and Engineering: A

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Section: Constitutive Equationsupporting

confidence: 82%

High tensile elongation of a directionally solidified NiAl multiphase alloy at high temperatures

Cui

Jianting

et al. 2005

Materials Science and Engineering: A

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“…Further observation on the interface between Cr(Mo) and NiAl phases shows a large number of interface dislocation networks formed, as exhibited in Figure 7b. According to past studies [12,24], Cr(Mo) and NiAl phases possess good interface matching, because they have the same crystal structure and a similar lattice constant, especially along the (100) crystallographic plane. The presence of interface dislocation indicates that there is great lattice distortion along the phase interface, which may be induced by the segregation of Ho or Hf atoms.…”

Section: Microstructure Characteristicmentioning

confidence: 98%

“…Hence, it has been thought to be a potential candidate for high-temperature structural materials that can endure severe oxidation and corrosion well [10,11]. Based on the previous research [1,12], the attractive properties of NiAl should be ascribed to its long-range ordered crystal structure, but this feature also results in its brittleness at low temperature. Though NiAl demonstrates wellimproved ductility at high temperature, its mechanical properties still cannot meet the requirements of structural parts with load at room temperature [13,14].…”

Section: Introductionmentioning

confidence: 99%

“…Nevertheless, the outstanding oxidation and corrosion resistance of NiAl makes it very attractive as a fixed part or protective shield [15]. Regardless, these applications also present requirements for NiAl-based materials, including room-temperature strength (800 MPa) and fracture toughness (18 MPa•m 1/2 ) [6,10,12]. Therefore, it is still a critical research issue to simultaneously enhance the fracture toughness and strength of NiAl-based materials.…”

Section: Introductionmentioning

confidence: 99%

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Influence of Strengthening Elements and Heat Treatment on Microstructure and Fracture Toughness of NiAl-Cr(Mo)-Based Eutectic Alloy

Wang

Xie

et al. 2023

Materials

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Due to their potential improvement of high-temperature properties, the refractory metal hafnium (Hf) and the rare earth holmium (Ho) have attracted much attention. In the present research, NiAl-Cr(Mo) eutectic alloys with different Ho and Hf additions were fabricated by conventional smelting method and heat-treated to study the synergetic influence of strengthening elements and heat treatment. The samples were characterized using XRD, SEM, and TEM, and the three-point bending test was performed to obtain fracture toughness. The results demonstrate that Hf addition leads to the formation of Ni2AlHf Heusler phase and that Ho promoted the formation of Ni2Al3Ho phase. The microstructure of the alloy is affected by thermal treatment, with the coarsening of eutectic lamellae after heat treatment. The mechanical properties are improved by Hf and Ho additions, with increased fracture toughness. Overall, this study provides insights into the microstructure and properties of NiAl-Cr(Mo) eutectic alloys and highlights the potential of Hf and Ho addition to improve room-temperature properties. Specifically, the as-cast NiAl-Cr(Mo)-Hf eutectic alloy contains a relatively fine NiAl/Cr(Mo) eutectic lamella but coarse eutectic cell with Ni2AlHf phase embellished along the cell boundary. Minor Ho addition induces the formation of Ni2Al3Ho phase, which leads to the coarsening of the intercellular region but contributes to the refining of eutectic cell. In addition, the synergetic effect of Ho and Hf promotes the precipitation of Ni2Al3Ho and Ni2AlHf phases in the intercellular zone and increases the interface dislocations. Heat treatment benefits the solid solution of Ni2Al3Ho and Ni2AlHf phases, which improves their size and distribution by secondary precipitation. The Ni2AlHf phase in the NiAl-Cr(Mo)-Hf eutectic alloy becomes fine and uniformly distributed, but the NiAl/Cr(Mo) eutectic lamella in the eutectic cell becomes coarse. In comparison, heat treatment mainly optimizes the size and distribution of the Ni2Al3Ho and Ni2AlHf phases in the NiAl-Cr(Mo)-Hf-Ho eutectic alloy. Furthermore, heat treatment helps to eliminate the interface dislocations in the large NiAl precipitates and the NiAl/Cr(Mo) phase interfaces, which also contributes to fracture toughness by decreasing stress concentration. Minor Ho addition decreases the fracture toughness of as-cast NiAl-Cr(Mo)-Hf eutectic alloy from 6.7 to 6.1 MPa·m1/2, which should be ascribed to the coarsened intercellular region including aggregated Ni2Al3Ho and Ni2AlHf phases. However, minor Ho-doped NiAl-Cr(Mo)-Hf eutectic alloy obtained the highest fracture toughness of 8.2 MPa·m1/2 after heat treatment. This improved fracture toughness should be mainly attributed to the refined and well-distributed Ni2Al3Ho and Ni2AlHf phases in the heat-treated NiAl-Cr(Mo)-Hf-Ho eutectic alloy.

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“…However, temperature plays a strong role on the microstructural stability; for example at relatively lower operating temperature γ′ disrupts the two-phase equilibria composed of γ and α [113]. Furthermore, Mo-modified β-NiAl bond coat also possesses superior strengthening effect than that of unmodified one which has been attributed to its refined microstructure [114]. Therefore, it is essential to have a knowledge of how Mo affects the phase stabilities of technologically relevant Ni-Al-based phases.…”

Section: Ternary Al-ni-mo Systemmentioning

confidence: 99%

Phase Stability, Structure and Thermodynamics of Modified Ni- and Fe-Aluminides

Santra

2017

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The Ni-aluminides are integral constituents of thermal barrier coatings applied over Ni-based superalloys. These aluminides provide oxidation-resistance by forming a protective α–Al2O3surface layer. The Pt-modified β–NiAl bond coat has been developed with an impetus to increase the service-life of Ni-based superalloys. The Pt-modified β–NiAl bond coat significantly improves the oxidation-resistance of superalloys. An interdiffusion zone containing topologically closed packed phases develops at the bond coat/superalloy interface. This eventually leads to Al-lean γ′–Ni3Al transformation, whose oxidation resistance is inferior to that of β–NiAl. The Pt-group metals Ir and Ru delay this transformation and impart creep-resistance to the bond coat. Recent investigations demonstrate that alloying with transition metals such as Cr, Mo and Fe enhance the mechanical strength. The functional stability of bond coat-superalloy assembly counts on the interfacial reaction and associated local structural variations which is a function of bond coat composition. This chapter elucidates the effect of various alloying elements on phase constitutions, crystallographic structural stability and thermodynamics of Ni-and Fe-aluminides to engineer a prospective bond coat.

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Superplasticity in NiAl and NiAl-based alloys

Cited by 8 publications

References 18 publications

High tensile elongation of a directionally solidified NiAl multiphase alloy at high temperatures

High tensile elongation of a directionally solidified NiAl multiphase alloy at high temperatures

Influence of Strengthening Elements and Heat Treatment on Microstructure and Fracture Toughness of NiAl-Cr(Mo)-Based Eutectic Alloy

Phase Stability, Structure and Thermodynamics of Modified Ni- and Fe-Aluminides

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