Effect of temperature on solid-state formation of bulk nanograined intermetallic Al₃Ni during high-pressure torsion

Abstract

A bulk form of nanograined intermetallic Al 3 Ni was produced by severe plastic deformation using high-pressure torsion (HPT). Powder mixtures of 75 mol% Al and 25 mol% Ni were processed by HPT at a selected temperature in the range of room temperature (RT) to 573 K under a pressure of 6 GPa. X-ray diffraction analysis revealed that the Al 3 Ni intermetallic formed after processing for 50 revolutions at RT but, as the processing temperature increased, less revolutions (i.e. lower imposed strain) were required for the formation of Al 3 Ni. Observations by transmission electron microscopy showed that the microstructure consists of ultrafine grains having a size of 300-2000 nm after 3 and 10 revolutions. Once the Al 3 Ni formed after a higher number of revolutions, equiaxed nanograins with a size of~30 nm prevailed with a significant increase in hardness. The increase in hardness was more significant when processed at higher temperatures because of increasing the fraction of Al 3 Ni. It was shown that the solid-state formation of Al 3 Ni occurred due to enhanced diffusion (i.e. decreased activation energy for diffusion) through the presence of high density of lattice defects.

Impact of severe plastic deformation on kinetics and thermodynamics of hydrogen storage in magnesium and its alloys

“…We reiterate that SPD is a useful group of processes to produce nano-sized grains decorated with crystal lattice defects [20]. As reviewed in [48,163,164], among the SPD processes, HPT is a unique method that is applicable to hard and brittle materials including intermetallics [165,166], glasses [167,168], ceramics [169,170] and semiconductors [171][172][173][174]. In particular, by taking this advantage, HPT was applied to an intermetallic Mg2Ni compound which gave rise to a significant improvement of the hydrogenation kinetics of the material due to the grain refinement down to the nanoscale [59].…”

Severe Plastic Deformation of Light Metals (Magnesium, Aluminum and Titanium) and Alloys by High-Pressure Torsion: Review of Fundamentals and Mechanical/Functional Properties

“…12,15) Such high shear strains are achieved by increasing the number of rotations in HPT. Strains up to 100000 with 1000-1500 HPT rotations were applied to some light metals based on magnesium, [103][104][105][106][107][108][109][110][111] aluminum, [112][113][114][115][116][117][118][119][120][121] and titanium, [122][123][124][125][126] as summarized in Table 1. It is noted that while the main issue in SPD is microstructural refinement, the target of ultra-SPD is solid-state reactions to synthesize new materials.…”

Superfunctional Materials by Ultra-Severe Plastic Deformation

“…Currently, ultra-SPD is considered an effective tool to produce a wide range of materials such as binary and ternary alloys and intermetallics [ 16 , 17 ], high-entropy alloys [ 30 ], metal hydrides [ 31 , 32 ], and high-entropy ceramics [ 33 ]. Table 1 summarizes the results of the application of ultra-SPD to different systems in the author’s group and summarizes the main achievements of each system [ 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 , 58 , 59 , 60 , 61 ]. As can be seen in Table 1 , the application of ultra-SPD is not limited to the synthesis of conventional metallic alloys, and it has been recently extended to ceramic materials.…”

“…Ultra-SPD can be used as a single-step process to synthesize ultra-hard bulk nanostructured intermetallics directly from the elemental powders. Several intermetallics such as various Mg-based intermetallics [ 43 ], AlNi [ 34 ], Al 3 Ni [ 36 , 38 ], TiAl [ 35 ], FeNi with the L1 0 structure [ 39 ] and Ni 2 AlTi [ 37 ] were synthesized in recent years by ultra-SPD or ultra-SPD followed by low-temperature annealing.…”