No abstract

High-pressure torsion (HPT) is one of the major severe plastic deformation (SPD) procedures where bulk metals, in the shape of a disk, achieve exceptional grain refinement at ambient temperatures. HPT has been applied for the consolidation of metallic powders and the bonding of machining chips whereas there are very limited reports examining the application of HPT for the production of new metal systems and the formation of nanocomposites. Accordingly, this investigation was initiated to evaluate the potential for the formation of a metal matrix nanocomposite (MMNC) by processing two commercial metal disks of an Al-1050 alloy and a ZK60 magnesium alloy through HPT under 6.0 GPa for 20 turns at room temperature. Evolutions in microstructure, mechanical properties including hardness and plasticity and the tribological properties were examined in the MMNC region of the processed Al-Mg system. The significance of post-deformation annealing (PDA) at 573 K for 1 hour was investigated by the change in microstructure and the enhancement in mechanical properties and wear resistance of the HPT-processed MMNC. This study demonstrates the promising feasibility of using HPT to fabricate a wide range of hybrid MMNCs from simple metals and for applying PDA for further improvement of the essential mechanical and tribological properties in the synthesized alloy systems.

Abstract

High-pressure torsion (HPT) is used to investigate the formation of a new metal system by the direct bonding of separate disks of Al and Cu by processing at room temperature under a compressive pressure of 6.0 GPa and with increasing numbers of HPT turns up to 60. A detailed examination of the microstructure and a phase analysis reveal the presence of three intermetallic compounds, Al 2 Cu, AlCu, and Al 4 Cu 9 , in the nanostructured Al matrix with a grain size of %30 nm. Processing by HPT leads to the formation of a metal-matrix nanocomposite with extreme hardness near the edge of the Al-Cu disks after 60 HPT turns. Experiments show that the estimated wear rates exhibit an improvement in wear resistance while maintaining low wear rates for high applied loads up to %40-50 N under dry sliding conditions. The results confirm that there is a significant potential for using HPT processing in the joining and bonding of dissimilar metals at room temperature and in the expeditious fabrication of a wide range of new metal systems having enhanced mechanical and functional properties.

Chalcogenide perovskites have emerged as a new class of electronic materials, but fundamental properties and applications of chalcogenide perovskites remain limited by the lack of high quality epitaxial thin films. We report epitaxial thin film growth of BaZrS3, a prototypical chalcogenide,