Structure and Mechanical Properties of AlMgSi(Cu) Extrudates Straightened with Dynamic Deformation

Abstract

Before artificial ageing, extruded aluminium profiles are subjected to stretching with a small cold deformation in the range of 0.5-2%. This deformation improves the geometrical stability of the extruded product and causes changes in the microstructure of the profile, which leads to the strain hardening of the material after artificial ageing. The work has resulted in the creation of the prototype of an original device, which is unique in the world, for the dynamic stretching of the extruded profiles after quenching. The semi-industrial unit is equipped with a hydraulic system for stretching and a pneumatic system for cold dynamic deformation. The aim of this research paper is to produce advantageous microstructural changes and increase the strength properties of the extruded material. The solution of the dynamic stretching of the profiles after extrusion is a great challenge and an innovation not yet practised. The paper presents the results of microstructural and mechanical investigations carried out on extruded AlMgSi(Cu) alloys quenched on the run-out table of the press, dynamically stretched under different conditions, and artificially aged for T5 temper. Different stretching conditions were applied: a static deformation of 0.5% at a speed of 0.02 m/s, and dynamic deformation of 0.25%, 0.5%, 1%, and 1.5% at speeds of 0.05 and 2 m/s. After the thermomechanical treatment of the profiles, microstructural observations were carried out using an optical microscope (OM) and a scanning electron microscope (SEM). A tensile test was also carried out on the specimens stretched under different conditions. In all the cases, the dynamically stretched profiles showed higher strength properties, especially those deformed at a higher speed of 2 m/s, where the increase in UTS was observed in the range of 7-18% compared to the classical (static) stretching. The microstructure of the dynamically stretched profiles is more homogeneous with a high proportion of fine dispersoids.

Keywords: AlMgSi(Cu) alloys; dynamic deformation; extrusion; mechanical properties; microstructure; straightening.

Figure 1

Device for the cold dynamic stretching of the extruded profiles from the AlMgSi(Cu) alloys, view from the face: 1—clamp jaw with elastomer; 2—aluminium profile; 3—clamp jaw on the right side; 4—dynamic force system; 5—pedestal.

Figure 2

Device for the cold dynamic stretching of the extruded profiles from the AlMgSiCu) alloys, view from the back and front.

Figure 3

Device for the cold dynamic stretching of the extruded profiles from the AlMgSi(Cu) alloys, view from the right side of the system.

Figure 4

Device for the cold dynamic stretching of the extruded profiles from the AlMgSi(Cu) alloys, view from the left side.

Figure 5

The 5 MN 4-inch extrusion press run-out table with water wave installation (a) and the profile from AlMgSi(Cu) alloy after extrusion with cooling by water on the run-out table (b).

Figure 6

The prototype device for the dynamic stretching of the extruded profiles from the AlMgSi(Cu) alloys—the photos from the experimental tests: (a) side view, (b) front view, (c) the close-up view of the clamp jaw and dynamic force system and (d) the sample of the extruded profile after the dynamic straightening.

Figure 7

The scanner GOM Atos Core 200 for optically measuring the geometry of the extruded profiles (a) and the scanned extruded profiles (b).

Figure 8

Microstructure of profiles extruded from alloy 1/1A and dynamically straightened at (a) ε = 1%, v = 0.05 m/s; (b) ε = 1.5, v = 0.05 m/s; (c) ε = 1%, v = 2 m/s; (d) ε = 1.5%, v = 2 m/s; SEM (The middle pictures are enlargements of the area marked by the yellow box in the pictures on the left).

Figure 9

Microstructure of profiles extruded from alloy 3/2A and dynamically straightened at (a) ε = 1%, v = 0.05 m/s; (b) ε = 1.5%, v = 0.05 m/s; (c) ε = 1%, v = 2 m/s; (d) ε = 1.5, v = 2 m/s; SEM (The middle pictures are enlargements of the area marked by the yellow box in the pictures on the left).

Figure 10

Microstructure of profiles extruded from alloy 6/3a and dynamically straightened at (a) ε = 1%, v = 0.05 m/s; (b) ε = 1.5%, v = 0.05 m/s; (c) ε = 1%, v = 2 m/s; (d) ε = 1.5%, v = 2 m/s; SEM (The middle pictures are enlargements of the area marked by the yellow box in the pictures on the left).

Figure 11

Microstructure of profiles statically straightened at ε = 0.5%, v = 0.05 m/s: (a) alloy 1/1A, (b) alloy 3/2A, and (c) alloy 6/3A; SEM (The middle pictures are enlargements of the area marked by the yellow box in the pictures on the left).

Figure 12

Illustrative outcomes of the chemical analysis depicting the particles within the microstructure of the alloy 3/2A-extruded profiles supersaturated during the press run. Noteworthy particles identified include β-Mg₂Si, Q-Al₅Cu₂Mg₈Si₆, and a phase comprising Al, Si, Fe, and Mn.

Figure 13

Illustrative outcomes of the chemical analysis depicting the particles within the microstructure of the alloy 6/3A-extruded profiles supersaturated during the press run. Noteworthy particles identified include β-Mg₂Si, Q-Al₅Cu₂Mg₈Si₆, and a phase comprising Al, Si, Fe, and Mn.

Figure 14

Microstructure of profiles extruded from alloy 1/1A: (a) statically straightened at ε = 0.5, $v$ = 0.05 m/s; (b) dynamically straightened at ε = 1.5, $v$ = 2 m/s; STEM.

Figure 15

Microstructure of profiles extruded from alloy 3/2A: (a) statically straightened at ε = 0.5, v = 0.05 m/s; (b) dynamically straightened at ε = 1.5, v = 2 m/s; STEM.

Figure 15

Microstructure of profiles extruded from alloy 3/2A: (a) statically straightened at ε = 0.5, v = 0.05 m/s; (b) dynamically straightened at ε = 1.5, v = 2 m/s; STEM.

Figure 16

Microstructure of profiles extruded from alloy 6/3A: (a) statically straightened at ε = 0.5, $v$ = 0.05 m/s; (b) dynamically straightened at ε = 1.5, $v$ = 2 m/s; STEM.

Figure 17

Stress/strain curves recorded during static tensile test of samples from alloys 1/1A (a), 3/2A (b), and 6/3A-extruded (c), statically and dynamically stretched and artificially aged.

Figure 18

Dependence of tensile strength (UTS) for extruded profiles of alloys (a) 1/1A, (b) 3/2A, and (c) 6/3A, subjected to press run cooling, static or dynamic straightening, and subsequent artificial ageing at 175 °C for 8 h.

Figure 19

Dependence of elongation (A) for extruded profiles of alloys (a) 1/1A, (b) 3/2A, and (c) 6/3A, subjected to press run cooling, static or dynamic straightening, and subsequent artificial ageing at 175 °C for 8 h.

Figure 20

Results of 3D optical scanning of profile of 60 × 40 × 2 mm extruded from alloy 1/1A and dynamically straightened at ε = 2.0, $v$ = 2 m/s.

Figure 21

Results of 3D optical scanning of profile of 60 × 40 × 2 mm extruded from alloy 3/2A and dynamically straightened at ε = 2.0, $v$ = 2 m/s.

Figure 22

Results of 3D optical scanning of profile of 50 × 30 × 3 mm extruded from alloy 6/3A and dynamically straightened at ε = 2.0, $v$ = 2 m/s.

Figure 23

Statistical analysis of dispersoids for extrudates from AlMgSi(Cu) alloys with different Cu contents after static or dynamic stretching.

Figure 24

Dynamic deformation effect depending on the alloy for the extruded profiles of the alloys 1/1A, 3/2A, and 6/3A subjected to press run cooling, static or dynamic straightening, and subsequent artificial ageing at 175 °C for 8 h.