Abstract
An aluminum-copper alloy (Al-2024) was successfully subjected to high-pressure torsion (HPT) up to five turns at room temperature under an applied pressure of 6.0 GPa. The Al-2024 alloy is used as a fuselage structural material in the aerospace sector. Mechanical properties of the HPT-processed Al-2024 alloy were evaluated using the automated ball indentation technique. This test is based on multiple cycles of loading and unloading where a spherical indenter is used. After two and five turns of HPT, the Al-2024 alloy exhibited a UTS value of ~1014 MPa and ~1160 MPa respectively, at the edge of the samples. The microhardness was measured from edges to centers for all HPT samples. These results clearly demonstrate that processing by HPT gives a very significant increase in tensile properties and the microhardness values increase symmetrically from the centers to the edges. Following HPT, TEM examination of the five-turn HPT sample revealed the formation of high-angle grain boundaries and a large dislocation density with a reduced average grain size of ~80 nm. These results also demonstrate that high-pressure torsion is a processing tool for developing nanostructures in the Al-2024 alloy with enhanced mechanical properties.
Highlights
Al-2024 is a high strength alloy at room temperature and even at elevated temperatures
The present paper reports on microstructural examinations and microhardness measurements carried out on a commercial Al-2024 alloy processed by high-pressure torsion (HPT)
It can be seen from the figure that, as the number of HPT turns increases, the overall Vickers microhardness across the disk surface increases and the microhardness in the outer region is always higher than in the centre for all HPT-processed disks
Summary
Al-2024 is a high strength alloy at room temperature and even at elevated temperatures. Severe plastic deformation (SPD) technologies provide new opportunities for developing nanostructures in metals and alloys with improved mechanical properties that are very attractive for various structural and functional applications [1]. The fine refinement in the structure of metals and alloys developed by modern methods of SPD has led to the development of newer ultrafine-grained (UFG) materials with a unique set of functional and service properties [2]. Among the various SPD techniques, HPT is especially attractive because it is easy to carry out, it has the ability to apply extremely high strains and it generally produces exceptionally small grain sizes. The applied pressure produces compressive stresses that are effective in preventing cracking of the sample, whereas the torsional straining developed by the anvil rotation produces severe plastic deformation of the thin disk. The intent was to explore the effectiveness of the HPT process for grain refinement and subsequent enhancement of mechanical properties in the Al-2024 alloy
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