Narrow Results

The structure and processes of mass, charge and heat transfer are investigated in an equiatomic Fe–Ni composite fabricated by electroconsolidation using the spark plasma sintering (SPS) technology. The system contains regions of almost pure Fe and Ni, separated by areas with variable concentration of components, formed in consequence of the interdiffusion in the electroconsolidation process. The interdiffusion coefficient of the Fe–Ni system has been revealed to be significantly higher than that of an alloy of a similar composition at the same temperature, which is likely the result of the employed SPS technology and the enhanced diffusion along the grain boundaries. The concentration dependence of the interdiffusion coefficient passes through a maximum at a Ni concentration of $\sim$70 at.%. The electrical and thermal conductivity of the studied system is significantly higher than that of an alloy of the same composition. The temperature dependence of the resistivity of the sample in the range 5–300 K is due to the scattering of electrons by defects and phonons, and the scattering of electrons by phonons fits well to the Bloch–Grüneisen–Wilson relation. The boundaries of the conductivity of the investigated composite correspond to the Hashin–Shtrikman boundaries for a three-phase system, if Fe, Ni and the FeNi alloy are selected as phases.

This study investigates the impact of initial temperature on the microstructure and mechanical properties of welded components, using molecular dynamics (MD). The stress–strain curves of the welded components, following various initial temperature treatments, revealed a double yielding phenomenon. Notably, there was a significant strain difference of 19.7% between the two yields. When the strain was loaded to the point of doubling yielding, stacking faults and twins covered the aluminum component part, while no such observations were made in the nickel component part. Additionally, tensile cracking occurred in the aluminum component part. The results indicate that treatment at varying initial temperatures alters the internal structure of the welded components. After the material yielded the first time, a significant number of disordered atoms and Shockley partial dislocations emerge, resulting in a substantial buildup of dislocation tangles and reduced dislocation migration rates. Consequently, the material exhibits a phenomenon of double yielding, with dislocation slip and deformation serving as the primary mechanisms. The optimal mechanical properties of the welded components achieved an initial temperature of 200K. Additionally, the effect of tensile temperature on the mechanical properties of the welded components were analyzed, and similar observations of double yielding were made. The significant number of dislocation tangles served as a barrier to dislocation slip, effectively enhancing the material’s mechanical properties. The simulation results provide theoretical support for the development of aluminum–nickel multilayer film self-propagation welding process.