Interfacial grain structure, texture and tensile behavior of multilayer deformation-based additively manufactured Al 6061 alloy

Characterisation of materials properties and defects in structure fabricated via additive friction stir deposition

“…8f at a kissing bond at the edge of the deposit. Tang et al [31] also observed this phenomenon but only at a kissing bond on the 9th layer of an 18-layer AFSD-manufactured Al6061 structure. This was attributed to two factors: the rst is energy stored in sub-grain boundaries driving sub-grain growth, and the second is consumption of neighbouring ne grains that completely recrystallised.…”

“…In FSW [54,55], friction stir processing (FSP) [54,56], and AFSD [31,49], plastic deformation and heat generation will induce dislocations. For materials with a high stacking fault energy, like aluminium [57],…”

“…This, in turn, diminishes the material's strain energy and initiates DRV, forming equiaxed subgrains with nearly dislocation-free interiors. Furthermore, prior boundaries respond to subgrain boundary interface tensions and become serrated, and when boundary separation approaches subgrain size, GDRX occurs [31,53,54].…”

“…Therefore, deposit in as-manufactured condition consists of recrystallised strain-free grains; however, these grains will grow if the material remains above its annealing temperature [31,53,55].…”

“…Tunnel defects, also known as wormhole defects, are an internal cavity formed along the tool traverse direction caused by improper plasticisation of the material and de cient material movement around the tool pin [29,30]. Flash and kissing bonds have been previously noted for AFSD [14,31]; although X ray tomography techniques have not yet been applied to charecterise shape, size and distribution in 3D of tunnel defects in AFSD [29]. The combination of optical microscopy and X-ray computed microtomography (XCT) can provide detailed visualisation of both internal defects and surface topography [32].…”