Research Progress of Aluminum Alloy Welding/Plastic Deformation Composite Forming Technology in Achieving High-Strength Joints

Abstract

Fusion welding causes joint deterioration when joining aluminum alloys, which limits the use of aluminum alloy components in high-end equipment. This paper focuses on an overview of how to achieve high-strength aluminum alloy welded joints using welding/plastic deformation composite forming technology. The current technology is summarized into two categories: plastic deformation welding and plastic deformation strengthening. Plastic deformation welding includes friction stir welding, friction welding, diffusion welding, superplastic solid-state welding, explosive welding, and electromagnetic pulse welding. Plastic deformation strengthening refers to the application of plastic deformation to the weld seam or heat-affected zone, or even the whole joint, after welding or during welding, including physical surface modification and large-scale plastic deformation technology. Important processing parameters of plastic deformation welding and their effects on weld quality are discussed, and the microstructure is described. The effect of plastic deformation strengthening technology on the microstructure and performance evolution, including the hardness, tensile strength, fatigue property, residual stress, and hot cracking of aluminum alloy welded joints, and its evolution mechanism are systematically analyzed. Finally, this paper discusses the future development of plastic deformation strengthening technology and anticipates growing interest in this research area.

Keywords: aluminum alloy; mechanical property; plastic deformation strengthening; plastic deformation welding.

Figure 1

Basic working principle of FSW [45].

Figure 2

(a) Fabricated tool for FSW with different shoulder profiles [61]; (b) geometries of pin profiles and weld joints created with different pins [62]; (c) gap-tolerance control window for friction stir butt welding of 2A14 aluminum alloy [57].

Figure 3

(a) The principle of friction stir welding assisted by carbon dioxide [78]; (b) schematic diagram of ultrasonic-assisted friction stir welding.

Figure 4

Schematic diagram of the friction welding process [85].

Figure 5

Microhardness distribution along the central line in the Al/Mg welded joints at different times [83]: (a) 1 s; (b) 3 s; (c) 5 s; (d) 10 s; (e) effects of the friction time on the tensile strength of Al/Mg welded joints.

Figure 6

Schematic diagram of the diffusion bonding apparatus [97].

Figure 7

SEM back-scattered electron images showing the interfacial layer of a specimen annealed [96,103] (a) for different times and (b) at different temperatures. Microhardness profiles (c) of the Al-Cu, Al-Ag (10 μm)-Cu, and Al-Ni (50 μm)-Cu joints, of which the bonding parameters are 520 °C/10 MPa/60 min, 460 °C/15 MPa/60 min, and 520 °C/15 MPa/60 min, respectively; microhardness profiles of (d) the Al-Ni (20 μm)-Cu and Al-Ni (50 μm)-Cu joints, of which the bonding parameters are 500 °C/10 MPa/60 min.

Figure 8

(a) Preparation process of the two-layer hollow structure of the 1420 Al-Li alloy. (b) two-sheet hollow structure of the 1420 Al-Li alloy [121].

Figure 9

(a) Explosive welding device of the clad tube. (b) TA1/Al clad tube prepared by explosive welding. (c,d) Morphology of the TA1/Al clad tube [123].

Figure 10

(a) Schematic diagram of resistance spot welding with a cover plate. (b) SEM images of the weld cross-section at the A5052/SUS304 interface [131].

Figure 11

Schematic principle of LSP.

Figure 12

EBSD characterization of laser-welded 7075 Al alloy joint [141]. (a) Microstructure zones of the weld zone after aging and ultrasonic impact treatments; (b) misorientation angle distribution; (c–e) Q1-Q3 inverse pole figure.

Figure 13

Schematic illustration showing the microstructure evolution process of LY12 Al alloy induced by multiple LSP impacts [139].

Figure 14

Geometry and rolling methods for [39,151] (a) rolling on top of the weld bead and (b) rolling beside the weld bead with the dual flat rollers; (c) mid-thickness longitudinal residual stress after rolling on top of the weld bead and different friction coefficients between the workpiece and the backing bar (μBB) and the roller (μR); (d) schematic diagram of welding hot cracking generation conditions.

Figure 15

Schematic of the rolling process [158,159,161]. (a) Partial rolling; (b) Entire rolling; (c) Rotation rolling.

Figure 16

Comparison between the mechanical behavior exhibited by the FSWed + CRed and BM+CRed samples in terms of [162]: (a) UTS vs. height reduction; (b) elongation vs. height reduction; (c) strain hardening exponent vs. height reduction; (d) elongation vs. strain hardening exponent.

Figure 17

(a) Tensile results; (b) fracture position (marked by yellow circle); (c) strengthening mechanisms of the SRA process [163].

Figure 18

Schematic diagram of the main rolling methods [170]: (a) Vertical with a profiled roller; (b) in situ rolling; (c) pinch rolling; (d) rolling with an inverted profiled roller for thick sections and intersections.