Ion Species/Energy Dependence of Irradiation-Induced Lattice Structure Transformation and Surface Hardness of Ni₃Nb and Ni₃Ta Intermetallic Compounds

Abstract

Bulk samples of Ni 3 Nb and Ni 3 Ta intermetallic compounds were irradiated with 16 MeV Au, 4.5 MeV Ni, 4.5 MeV Al, 200 MeV Xe and 1.0 MeV He ions, and the change in near-surface lattice structure was investigated by means of the grazing incidence x-ray diffraction (GIXD) and the extended x-ray absorption ne structure (EXAFS). The Ni 3 Nb and Ni 3 Ta lattice structures transform from the ordered structures (orthorhombic and monoclinic structures for Ni 3 Nb and Ni 3 Ta, respectively) to the amorphous state by the Au, Ni, Al and Xe ion irradiations. Irrespective of such heavy ion species or energies, the lattice structure transformation to the amorphous state almost correlate with the density of energy deposited through elastic collisions. In the case of the samples irradiated with 1.0 MeV He ions, however, no amorphization was observed even when the density of elastically deposited energy is the same as that for Au irradiated sample which showed the amorphous phase. The change in Vickers hardness induced by the amorphization was also measured and was discussed in terms of ion uence and the density of deposited energy.

Modification of Lattice Structures and Mechanical Properties of Metallic Materials by Energetic Ion Irradiation and Subsequent Thermal Treatments

“…The effect of the thermal treatments, which were performed after the irradiation, on the lattice structure and the hardness was also investigated. The details of the experimental procedure have been described in our previous reports [13,20]. Figure 16 shows the phase diagram for Ni-V binary alloy and the schematic diagram of the D0 22 and A1 lattice structures.…”

“…They are more sensitive against the energetic ion irradiation than pure metals or dilute alloys, because not only atomic displacements but also position exchanges of atoms of different types affect their atomic arrangements and physical properties. For the past decade, we have studied the effects of energetic ion irradiation on the lattice structures and the hardness of several Ni-based intermetallic compounds (Ni 3 V [11,13], Ni 3 Al [16], Ni 3 Nb [18,20,21], and Ni 3 Ta [18,20,21]). As the specimens were sufficiently homogenized at elevated temperatures for a long time, the lattice structures of the specimens before the irradiation are consistent with the structures that are present in the thermal equilibrium phase diagrams at room temperature and atmosphere pressure.…”

“…However, such studies for nuclear power plants and space developments have treated the negative effects of ion irradiation (so-called "radiation damage") on materials' properties. In our recent studies, we have positively used the energies deposited by energetic ion/electron irradiation for the modification of materials properties such as the mechanical properties [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23], magnetic properties [24][25][26][27][28][29][30][31][32][33][34][35][36][37], and optical properties [38] of metallic and oxide materials.…”

“…In the following chapters, we will summarize our recent experimental results about the modification of the hardness by ion irradiations for two kinds of metallic materials; dilute aluminum alloys [7][8][9]17,19] and nickel-based intermetallic compounds [11,13,15,16,18,20,21]. The former is an example of the materials' modification through the irradiation-enhanced process, and the latter is that through the irradiation-induced process.…”

Thermal stability of irradiation-induced metastable lattice structures in NiTi intermetallic compound

“…Therefore, they are more sensitive against the ion irradiation than pure metals or normal alloys, because not only the atomic displacements but also the position exchange of atoms of different type affect their properties. We have reported so far the effect of energetic ion irradiation for several Ni-based intermetallic compounds from the perspective of phase transition, mechanical property and short range order of lattice structures [1][2][3][4][5]. As the irradiation induced lattice structures are metastable states which are far from the thermal equilibrium states, we have also investigated the thermal stability of ion irradiation induced lattice structures of Ni-based intermetallic compounds (Ni3Al, Ni3V, Ni3Nb and Ni3Ta) [2,6,7].…”