Effect of Severe Plastic Deformation on the Structure and Properties of the Aluminum Alloy System Al-Cu-Mg

Abstract

The structure and properties of discs from cast coarse-grained D16 alloy have been investigated with the help of optical metallography and transmission electron microscopy, after the traditional heat treatment (HT) modes or subjected to high pressure torsion (HPT) under pressure in 6 GPa at room temperature. Standard HT modes included: Т4 (hardening 495°С + natural aging at room temperature for 5 days) and Т6 (hardening 495°С + artificial aging at 185°С for 10 hours). It is shown that after HT of alloy D16 according to modes T6 and Т4, the sizes of the structural elements, compared with the original, decreased by about 4,8 times and the microhardness increased by 1,6 times. It is shown that after one or ten rotates of HPT in D16 alloy the sizes of structural elements, in comparison with initial, decreased by 393 and 899 times, and microhardness increased by 2,4 and 2,9 times, respectively. Detection of hardening hard, brittle and high-alloy copper γ2- phases (Cu9Al4) indicates the passage in the HPT process of the decomposition of a supersaturated solid solution (dynamic aging) in the planes of a local shift.

Low-Temperature Superplasticity and High Strength in the Al 2024 Alloy with Ultrafine Grains

“…In the Al grain interiors, we observed individual globular particles of the strengthening phase with a size up to 5 nm. According to [ 6 , 7 , 8 , 17 ], the particles refer to the S(Al 2 CuMg) phase. In addition, authors in [ 8 , 17 , 18 , 19 ] noted the formation of Cu segregations at the boundaries of Al grains, which facilitates grain-boundary sliding in the process of superplasticity at lower temperatures [ 4 , 20 ].…”

“…The spots are distributed circularly on the diffraction pattern, which is indicative of high-angle misorientations of grain boundaries formed during HPT [ 21 ]. Besides the noted reflections, in the electron diffraction patterns additional reflections can be seen ( Figure 1 a), which belong to the secondary strengthening phase [ 6 , 7 , 8 , 17 ].…”

“…To find the thermal stability of the UFG 2024 alloy, a series of one-hour annealings in a range of 120–270 °C were carried out. The interval of one-hour annealings for finding the alloy’s thermal stability was selected on the basis of the previously published studies, including those on the thermal stability of the 2024 alloy in the UFG state [ 5 , 6 , 7 , 18 ]. Figure 2 b shows the dependence of microhardness on the temperature of one-hour annealing of the UFG 2024 alloy.…”

“…Such a high level of properties produced in the material under study is determined, in addition to grain refinement to 70 nm and a high dislocation density, by an interaction of dislocations with the precipitates of the particles of the T(Al 20 Cu 2 Mn 3 ) and S(Al 2 CuMg) phases which control the intensity of dynamic recovery and recrystallization. However, the high strength of this UFG Al alloy 2024 is quickly lost after heating above 200 °C when recrystallization processes occur in the alloy and grain growth takes place [ 7 , 8 ]. In this connection, the superplastic forming of this alloy realized at temperatures of 450–500 °C for producing complex-shaped items ensures, in these items, strength below 250–300 MPa.…”

IMPROVING THE MECHANICAL PROPERTIES OF Al-Cu-Mg-Mn ALLOY TUBES THROUGH PLASTIC DEFORMATION

“…Therefore, it is important to find ways to improve the mechanical properties while maintaining the lightness and specific strength of aluminum alloys. Modern approaches to this problem include ultrafine grinding of the alloys' grain structure by methods such as plastic deformation [1][2][3][4][5][6][7], as well as heat treatment methods such as annealing by stimulating static recrystallization [8], and aging after hardening and high-pressure torsion [9]. In fact, plastic deformation is often applied to increase the mechanical properties of a solid material [10][11][12][13][14].…”