Mechanical Bonding of Aluminum Hybrid Alloy Systems through High‐Pressure Torsion

Abstract

The present study demonstrates an innovative approach of utilizing high‐pressure torsion (HPT) processing for the mechanical bonding of dissimilar metals during the microstructural refinement process. This processing approach has been developed recently for introducing unique alloy systems with improving physical and mechanical properties. Accordingly, the present study focuses specifically on the microstructural evolution and development in micro‐mechanical responses in the mechanically bonded Al‐Mg and Al‐Cu hybrid alloy systems when synthesized by HPT processing for very high number of turns up to 60 under 6.0 GPa at room temperature. The microstructural and hardness evaluations confirm the capability of the HPT procedure for the formation of heterostructures with extreme hardness at the disk peripheries and with low hardness at the disk centers in these processed alloy systems. Nanoindentation measurements demonstrate that both hybrid alloy systems exhibit excellent plasticity at the disk edges, where the hardness is the highest. There is a considerable potential for applying the solid‐state reaction through the HPT process for the bonding of dissimilar metals as a manufacturing technique and for the development of hybrid alloy systems.

Size Effect on Microstructural Evolution and Micromechanical Responses of Mechanically Bonded Aluminum and Magnesium by High‐Pressure Torsion

“…In this way, the strain rate sensitivity was calculated as m ¼ 0.05 after 10 turns and 0.04 after 20 turns under 1.0 GPa. Although there is no earlier data of the m value available for the HPT disk having 25 mm diameter, these estimated m values taken at r ¼ 10 mm for the Al-Mg disks are higher than 0.02 for the base material of the Al disk with 10 mm diameter when processed by HPT for 10 turns at 6.0 GPa [39] and are similar or slightly higher than 0.035-0.045 for the ZK60 disk with 10 mm diameter after 2 HPT turns measured by nanoindentation. [40] Thus, the mechanically bonded Al-Mg disks having 25 mm diameter show excellent plasticity with holding high hardness at the disk edges.…”

Synthesis of Hybrid Nanocrystalline Alloys by Mechanical Bonding through High‐Pressure Torsion

“…In practice, intensive studies were conducted on the diffusion bonding of Al/Mg/Al, and Figure 9 shows the structural and hardness evolution of Al-Mg mechanical bonding by HPT under 6 GPa for 1, 5, 10, 20, 40, and 60 turns. Specifically, a series of micrographs taken at the cross-sectional planes are shown in Figure 9a, [35,38,55] where the dark phase represents the Mg-rich and the bright phase represents the Al-rich phase, the hardness variation at the disk diameter for the corresponding disks is shown in Figure 9b, [55] where the dotted horizontal lines are the reference saturation hardness values observed for the Al-1050 [56] and ZK60 [57] alloys after HPT for 5 turns, and an XRD peak profile is shown in Figure 9c at the disk edge of the Al-Mg system after 20 HPT turns. [38] It is apparent after 1 HPT turn that a multilayered structure remains throughout the disk diameter with the fragmented Mg layers having thicknesses of %200 μm, and with no visible segregation at the Al-Mg interfaces.…”

“…Reproduced with permission. [38] Copyright 2017,Elsevier [55] ; Copyright 2019, Wiley. Reproduced with permission.…”

“…The regions of severely mixed phases appear at the disk edges in general, and they extend with increasing numbers of HPT turns, as is shown in the Al-Mg and Al-Cu systems in Figure 9 and 10, respectively. Taking a boundary radius, r b , which is the distance from the disk center dividing the multilayered structure from the severe mixture of metal phases at the disk edges, Figure 13 shows a relationship between r b and the estimated equivalent strain and the shear strain computed using Equation (1) for both mechanically bonded Al-Mg [35,38,55] and Al-Cu [40] systems after HPT at 6.0 GPa. [55] It is apparent that there is an approximate linear relationship between r b and strain for both alloy systems, whereas the rate of change in r b depends on the selection of dissimilar metals.…”

“…Taking a boundary radius, r b , which is the distance from the disk center dividing the multilayered structure from the severe mixture of metal phases at the disk edges, Figure 13 shows a relationship between r b and the estimated equivalent strain and the shear strain computed using Equation (1) for both mechanically bonded Al-Mg [35,38,55] and Al-Cu [40] systems after HPT at 6.0 GPa. [55] It is apparent that there is an approximate linear relationship between r b and strain for both alloy systems, whereas the rate of change in r b depends on the selection of dissimilar metals. This analysis implies, therefore, that there is a possibility to expand the regions with a severe mixture of dissimilar metal phases to achieve a homogeneous microstructure within the entire metal volume when applying a much higher strain by HPT.…”