Effect of Al, Cr, Mo, Zr, Si, and C on the temperature ranges of hardening of multicomponent niobium-based alloys

The effect of alloying and the strain rate on the occurrence and features of the manifestation of temperature ranges in which the strengthening of niobium alloys doped with Ti, Al, Cr, Mo, Zr, Si, C occurs was studied. It was found that in multicomponent solid solutions based on niobium up to sufficiently high temperatures more efficient hardening is provided than in precipitation hardened carbide alloys. It is shown that in multicomponent niobium alloys, which are a solid solution, the selection of alloying can be used to control the manifestation of a high-temperature hardening peak in a wide range. It is possible to change the temperature range of the peak manifestation, its height, sensitivity to the strain rate. The appearance of a high-temperature hardening peak is explained by the loss of stability of the multicomponent solid solution upon deformation in the dislocation field, which leads to the precipitation of dispersed particles of the second phase that pin the dislocations. Keywords: multicomponent niobium alloys, structure, temperature dependence of strength.

Composition Dependent Diffusivities in Multi-Component Systems

The modified Redlich-Kister approximation of the composition dependent intrinsic diffusivities in the multicomponent solid solution is presented. The effective computation method (the inverse problem) combines the Hierarchical Genetic Strategy with real number encoding (HGS-FP) with the modified Redlich-Kister approximation. The Cu–Ni–Fe alloys at 1271 K are analyzed. We show that the measured intrinsic diffusivities, the estimated from available diffusivity data and calculated by inverse method are in agreement. The presented method may become a very effective tool when the diffusion multiple technique is considered.

Electro-Mechano-Chemistry; Transport Problem in Four Time Scales

The mass transport in the presence of stress, electrical, mechanical and chemical potential gradients in multicomponent solid solution is analyzed. The method bases on the Darken concept and the calorimetric equation of state. We effectively coupled the conservation of the mass (continuity equations), energy, momentum and Gauss equations. The diffusion fluxes of the components are given by the Nernst-Planck formulae and take into account the electro-chemical and mechanical potentials. We simulate the deformation field during the diffusion caused by the gradients of the chemical potential of all elements in non-ideal Fe-Cu-Ni alloy. The simulations show that the model is compatible with experimental results, and can be effectively used for modelling the energy, momentum and mass transport problems in compressible multicomponent solid solutions. The numerical problems and methods of solution are presented.