Synthesis of a bulk nanostructured metastable Al alloy with extreme supersaturation of Mg

Abstract

Nanostructuring of bulk metals is now well documented with the development of severe plastic deformation (SPD) for improving the physical and mechanical properties of engineering materials. Processing by high-pressure torsion (HPT), which was developed initially as a grain refinement technique, was extended recently to the mechanical bonding of dissimilar metals during nanostrcturing which generally involves significant microstructural heterogeneity. Here we introduce, for the first time, a bulk metastable Al-Mg supersaturated solid solution by the diffusion bonding of separate Al and Mg metal solids at room temperature using HPT. Exceptional hardness was achieved homogeneously throughout the metastable alloy with a record maximum supersaturated Mg content of ~38.5 at.% in the Al matrix having a grain size of ~35–40 nm. Our results demonstrate the synthesis of a bulk nanocrystalline metastable alloy with good microstructural stability at room temperature where such bulk solids are not yet reported for mechanical alloying by powder metallurgy.

Anomalous critical point behavior in dilute magnetic semiconductor (Ca,Na)(Zn,Yu1, Liu2, Zhao3 et al. 2020Phys. Rev. Materials4160View full textAdd to dashboardCite

“…Recently a new class of DMS materials has been discoverede.g., Li 1+x (Zn,Mn)As, termed "111-type", and (Ba,K)(Zn,Mn) 2 As 2 , termed "122"in which carrier doping and spin doping are independent from each other, thus overcoming the difficulty just described [15][16][17][18][19][20][21]. For example, in (Ba,K)(Zn,Mn) 2 As 2 the isovalent substitution of Mn 2+ for Zn 2+ enables one to achieve high-Mn solubility (up to ~15% or more) in thermodynamic equilibrium, while substitution of K + for Ba 2+ produces charge carriers (holes) [22,23].…”

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

“…In contrast, a recent report on a continuous HPT processing for an efficient amount of high shear strain demonstrated, for the first time, a bulk nanostructured metastable Al alloy in a supersaturated solid‐solution state . Specifically, a set of Al and Mg disks arranged with the stacking order of Al/Mg/Al was mechanically bonded by HPT for 100 turns under 6.0 GPa at RT.…”

“…In contrast, a recent report on a continuous HPT processing for an efficient amount of high shear strain demonstrated, for the first time, a bulk nanostructured metastable Al alloy in a supersaturated solid-solution state. [123] Specifically, a set of Al and Mg disks arranged with the stacking order of Al/Mg/Al was mechanically bonded by HPT for 100 turns under 6.0 GPa at RT. The cross-sectional microstructure and the TEM micrographs taken at the disk edge and center as well as the corresponding hardness distribution at the cross-section are shown in Figure 21a for the synthesized Al-Mg alloy disk after 100 HPT turns.…”

“…a) Cross‐sectional microstructure, TEM micrographs taken at the disk edge and center, and the corresponding hardness distribution at the cross‐section of the synthesized Al–Mg alloy disk after 100 HPT turns and b) the XRD profiles of the mechanically bonded Al–Mg system after HPT for 100 turns and HPT processing followed by natural aging for 60 turns with the reference XRD profiles of an as‐received Al and Al after HPT for 5 turns. Reproduced with permission . Copyright Year 2019, Springer Nature.…”

“…Figure b shows the XRD profiles of the mechanically bonded Al–Mg system after HPT for 100 turns and HPT processing followed by natural aging for 60 turns to evaluate the structural stability: also included are reference XRD profiles of as‐received Al and Al after HPT for 5 turns . This evaluation provides an interesting finding that the Al–Mg system after 100 turns and additional annealing shows the FCC peaks for Al without any peaks for Mg or intermetallic phases, whereas the material volume remains unchanged after 20 HPT turns.…”