Ultrahard and super-stable pure aluminum with Schwarz crystal structure

ABSTRACT

Refining grains to sub-10 nm size is extremely difficult in pure aluminum due to its high stacking fault energy and low melting point. Herein, we experimentally demonstrate that Schwarz crystal (SC) structure with minimal interfaces constrained by coherent twin boundaries was induced in extremely fine grains (6 nm) of pure aluminum (99.995%) under extremely high shear strain via cryogenic high-pressure torsion. The SC structure exhibits an unprecedented hardness of 2.51 GPa and keeps stable up to 928 K (about 0.99 T_m).

GRAPHICAL ABSTRACT

IMPACT STATEMENT

Ultrahard and ultrastable pure aluminum with Schwarz crystal structure has been produced in extremely fine grains under extremely high shear strain via cryogenic high-pressure torsion.

KEYWORDS:

• Pure aluminum
• Schwarz crystal structure
• thermal stability
• grain refinement

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was financially supported by the National Natural Science Foundation of China (grant number 52101161 and 52225102), the Young Elite Scientists Sponsorship Program by CAST (grant number 2022QNRC001), the Postdoctoral Science Foundation of China (grant number 2021M693228) and the Ministry of Science and Technology of the People's Republic of China (grant number 2017YFA0700700).