The physical and mechanical metallurgy of Ni3Al and its alloys is reviewed Emphasis is on developments within the past five years, a period of extremely rapid growth in research on the behaviour of this unusually interesting intermetallic compound This review is particularly concerned with solute effects on properties such as diffusion rates, ductility, fatigue resistance, and environmental stability, subjects that only recently have received much attention Novel processing techniques, including rapid solidification and powder processing, are shown to have played a key role in providing Ni3Al-base alloys with improved properties An assessment of needed areas of research to hasten commercial applications of Ni3Al alloys concludes the review

Physical and mechanical metallurgy of Ni3Al and its alloys

The embedded atom method [M. S. Daw and M. I. Baskes, Phys. Rev. B 29, 6443 (1984) used to calculate phase stability, lattice vibrational frequencies, point defect properties, antiphase boundary energies, and surface energies and relaxations for Ni3Al. The empirical embedding functions and core-core repulsions used by this method are obtained. The equilibrium phases for the Ni-rich half of the composition range of Ni–Al are determined for 1000 K and compared with experiment. The elastic constants and vibrational modes of Ni3Al are calculated and the elastic constants are compared with experiment. The formation energy, formation volume, and migration energies of vacancies are computed, and it is found that the formation energy of vacancies on the Ni sublattice is less than that on the Al sublattice. The (100) antiphase boundary is shown to be significantly lower in energy than the (111) antiphase boundary. The surface energies and atomic relaxations of the low index faces are computed, and it is shown that for the (100) and (110) faces that the preferred surface geometry corresponds to the bulk lattice with the mixed composition plane exposed.

Application of the embedded atom method to Ni 3 Al

Amorphization of intermetallic compounds under irradiation - A review

Tracer diffusion in pure and boron-doped Ni3Al☆☆☆

Diffusion of nickel in the intermetallic compound Ni 3 Al is measured in the temperature range from 1004 to 1422 K by applying two different techniques for the determination of the concentration profiles. The diffusion of the radioactive 63 Ni tracer in Ni 3 Al polycrystals (75.2 at% Ni) is analyzed in the temperature region from 1223 to 1422K by the conventional serial sectioning technique using a precision parallel grinding device and an improved technique of detecting the low-energy β-decays of 63 Ni with high efficiency by liquid scintillation counting. In the low-temperature region (1004 to 1259 K) the concentration profiles are determined by secondary ion mass spectrometry (SIMS) using the highly enriched stable 64 Ni tracer and Ni 3 Al single crystals (75.9 at% Ni). The SIMS technique is considered as particularly suitable for profile detection, owing to its potential of measuring also low diffusion coefficients with high accuracy. The temperature dependence of the diffusion coefficient D v Ni follows a perfect linear Arrhenius relation in the investigated temperature range for Ni 3 Al. The frequency factor D 0 = (3.59 -1.50 +2.59 x 10 -4 m 2 s -1 and the activation enthalpy Q = (303.0 ± 5.3) kJ mol -1 correspond to a vacancy mechanism. An enhanced diffusivity at lower temperatures, which was previously reported in the literature and ascribed to the presence of constitutional vacancies, is not observed. It is concluded that Ni self-diffusion in Ni 3 Al only occurs via thermal vacancies. This result is in agreement with recent positron annihilation studies by Badura and Schaefer where, independent of the composition, no constitutional vacancies are detected in the Ni 3 Al compound.

A. Dasgupta

Papers

Positron annihilation study of boron-doped Ni3Al☆