Ni₃Al-based superalloys have excellent mechanical properties which have been widely used in civilian and military fields. In this study, the mechanical properties of the face-centred cubic structure Ni₃Al were investigated by a first principles study based on density functional theory (DFT), and the generalized gradient approximation (GGA) was used as the exchange-correlation function. The bulk modulus, Young’s modulus, shear modulus and Poisson’s ratio of Ni₃Al polycrystal were calculated by Voigt-Reuss approximation method, which are in good agreement with the existing experimental values. Moreover, directional dependences of bulk modulus, Young’s modulus, shear modulus and Poisson’s ratio of Ni₃Al single crystal were explored. In addition, the thermodynamic properties (e.g., Debye temperature) of Ni₃Al were investigated based on the calculated elastic constants, indicating an improved accuracy in this study, verified with a small deviation from the previous experimental value.

As a technology for micro-deformed solid-phase connection, transient liquid phase (TLP) diffusion bonding plays a key role in the manufacture of heating components of aero engines. However, the harmful brittle phase and high hardness limit the application of TLP diffusion bonding in nickel-based superalloys. In this paper, a new strategy in which a low-boron and high-titanium interlayer can restrain the brittle phase and reduce the hardness of the TLP-diffusion-bonded joint is proposed. With this strategy, the Ni₃Al joint can achieve a high strength of 860.84 ± 26.9 MPa under conditions of 1250 °C, 6 h and 5 MPa. The microhardness results show that the average microhardness of the joint area is 420.33 ± 3.15 HV and is only 4.3% higher than that of the Ni₃Al base material, which proves that this strategy can effectively inhibit the formation of the harmful brittle phase in the joint area. The results of EBSD show that 7.7% of the twin boundaries exist in the isothermal solidification zone, and only small amounts of secondary precipitates are observed at the grain boundaries in the joint, which indicates that twin boundaries may play a dominant role in crack initiation. This study provides a feasible avenue to suppress the brittle phase in TLP-diffusion-bonded joints.

Single-crystalline Ni₃Al-based superalloys have been widely used in aviation, aerospace, and military fields because of their excellent mechanical properties, especially at extremely high temperatures. Usually, single-crystalline Ni₃Al-based superalloys are welded together by a Ni₃Al-based polycrystalline alloy via transient liquid phase (TLP) bonding. In this study, the elastic constants of single-crystalline Ni₃Al were calculated via density functional theory (DFT) and the elastic modulus, shear modulus, and Poisson’s ratio of the polycrystalline Ni₃Al were evaluated by the Voigt–Reuss approximation method. The results are in good agreement with previously reported experimental values. Based on the calculated mechanical properties of single-crystalline and polycrystalline Ni₃Al, three-dimensional finite element analysis (FEA) was used to characterize the mechanical behavior of the TLP bonded joint of single-crystalline Ni₃Al. The simulation results reveal obvious stress concentration in the joint because of the different states of crystal orientation between single crystals and polycrystals, which may induce failure in the polycrystalline Ni₃Al and weaken the mechanical strength of the TLP bonded joint. Furthermore, results also show that the decrease in the elastic modulus of the intermediate layer (i.e., polycrystalline Ni₃Al) can relieve the stress concentration and improve the mechanical strength in the TLP bonded joint.

Ni3Al-based superalloys have excellent mechanical properties which have been widely used in civilian and military Fifield. In this study, the influence of the residual thickness of the interlayer on the stress-strain state in the nodes with soft interlayer was investigated by ccomputer simulation.To establish the general patterns of SSS formation when loading cylindrical nodes with interlayers of soft rigidity and checking the adequacy of the simulation, thickness of interlayer (0.01, 0.03, 0.05, 0.08mm) were calculated. The result shows that in all the thicknesses of the interlayer, both in the main material and in the interlayers, the nature of the distribution and the magnitude of the stiffness coefficients of the stressed state kstiff are practically identical. In the base metal, over most of the joint length, this coefficient is close to 1, decreasing to 0.88 in the nodes with “soft”. This corresponds to the general laws of mechanics and confirms the adequacy of the results of computer simulation.

The diffusion brazd test of IC10 superalloy was carried out by using Russia solder M3 interlayer powder. The wetting quality of the high-temperature alloy was evaluated by the contact angle of wetting at various temperatures. The mechanical properties of the joints were determined at operating temperatures. The result shows that at the temperature of 1250°C, the contact angles of interlayer powder M3 alloy do not exceed 4∼5°, it has high wettability and spread ability over the surface of the IC10 alloy. The average test time before failure at the temperature of 900° and the stress of 320 MPa was 38 hours, and at the stress of 350 MPa was 9.6 hours, all both higher than 80% of the base material under the same experimental conditions. The structure of the joints has a smooth transition from the base metal to the soldered joint. In the structure of the joint, the γ’- phase with a large volume concentration in the base metal. IC10 superalloy has excellent high temperature properties when the M3 interlayer was used.

The microstructure and composition of IC10 superalloy containing B (0 wt% 1.1 wt%) were studied in this paper. DSC and microstructure analysis were used to compare the formation process of the microstructure and composition of the IC10 alloy with or without boron content. Precipitation temperatures and sequence of initial phases of IC10 alloys with or without B content were researched. The results shows that the exothermal peaks of formation for γ, MC carbide, (γ+γ’) eutectic and secondary γ’ phase reveal on DSC cooling curves. The alloys with 1.1% B have amephase component and the formation sequence of six phasesis γ, MC, (γ+γ’) eutectic, secondary γ’, M3B2 and Ni5Hf in turn. The boron content enhances the volume fraction of M3B2 and (γ+γ’) eutectic, decreases the temperature of liquids and solidus and also delays the formation of MC and (γ+γ’) eutectic obviously.