Structure and Mechanical Behavior of Al–Nb Hybrids Obtained by High‐Pressure‐Torsion‐Induced Diffusion Bonding and Subsequent Annealing

Abstract

The main approach of mechanical consolidation of dissimilar metals consists in solid state joining of thin discs or powders by means of pressure‐assisted shear deformation. Prior to this research, most strongly dissimilar systems, such as Al–W and Al–Ti, were only bonded by means of mechanical alloying and subsequent powder compaction. Herein, pioneering experimental research on the one‐step synthesis of an Al–Nb composite by means of diffusion bonding through high‐pressure torsion that allows figuring out several unusual results is presented. The maximal microhardness value is revealed to locate in the middle radius area, decreasing at the sample edge. Formation of a small amount of Al3Nb intermetallic phase is detected at room temperature deformation, while its equilibrium formation normally occurs above 600 °C. Post‐deformational annealing at 400 °C results in the overall decrease of the microhardness value along with its growth on the sample edge. Annealing at 600 °C does not lead to any degradation of the mechanical characteristics by comparison to those after annealing at 400 °C. The obtained results are discussed and explained in frames of contribution of different factors to the strengthening and softening dynamics of the composite material.

Fabrication of Magnesium-Aluminum Composites under High-Pressure Torsion: Atomistic Simulation

“…In the present work, no effect is observed after annealing of the compressed samples, which is in contradiction with previous experimental results on the Al-Cu interface [9,10,12,13,17]. This can be explained by the difference in the metals used for composite fabrication, the weaknesses of the methodology, or by the lack of understanding of how to find better annealing temperatures.…”

“…Molecular dynamics simulation was used to study and analyze atomic movement on the Al-Mg interface under high pressure combined with shear strain. The proposed model was based on the scenario, experimentally observed previously in [9,10,12,13,17] for Al-Nb and Al-Cu composites. It is found that compression combined with shear is an effective method to obtain composite structure on the Al-Mg interface.…”

“…In the experiment [9,10,12,13,17], annealing at 450 • C is applied after the initial deformation of the Al-Cu composite. It is observed, that after annealing, two more intermetallic phases have appeared in the structure, and microhardness increase two times.…”

“…One of the possible ways to obtain metallic composites is high-pressure torsion (HPT), during which high compressive and shear stresses result in the formation of the composite structures. To date, several types of composite materials were obtained by HPT from metallic plates: Al-Cu [7][8][9][10][11][12][13], Al-Mg [14][15][16], Al-Nb [17], and Al-Ti [18]. Since severe plastic deformation can increase the diffusion in the materials [19,20], in situ composites can be obtained by HPT through the bonding of different metals, which can lead to the formation of new intermetallic phases.…”

Effect of annealing on the structure and phase composition of Cu-Al composite produced by conventional and accumulative HPT

“…Conventional HPT was successfully applied to obtain composites with a metal matrix in various binary systems: Al-Cu [11][12][13][14][15], Cu-Al [10,11,16,17], Al-Mg [18 -20]. Al-Nb [21,22], Zn-Mg [23], Zr-Nb [24]. To obtain composites with a metal matrix, a stack of dissimilar plates is deformed with HPT.…”