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Microstructural and mechanical characterisation of a second generation hybrid metal extrusion & bonding aluminium-steel butt joint

DOI: 10.1016/j.matchar.2020.110761 DOI Help

Authors: Tina Bergh (Norwegian University Norwegian University of Science and Technology (NTNU)) , Lise Sandnes (Norwegian University of Science and Technology (NTNU)) , Duncan Neil Johnstone (University of Cambridge) , Øystein Grong (Norwegian University of Science and Technology (NTNU)) , Filippo Berto (Norwegian University of Science and Technology (NTNU)) , Randi Holmestad (Norwegian University of Science and Technology (NTNU)) , Paul Anthony Midgley (University of Cambridge) , Per Erik Vullum (Norwegian University of Science and Technology (NTNU))
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Materials Characterization

State: Published (Approved)
Published: November 2020
Diamond Proposal Number(s): 20527

Open Access Open Access

Abstract: Hybrid metal extrusion & bonding (HYB) is a joining method that enables solid-state bonding by combining addition of aluminium filler material through continuous extrusion with pressure exerted by a rotating steel tool. This work presents mechanical and microstructural characterisation of a second generation HYB butt joint of aluminium alloy 6082 and structural steel S355. The ultimate tensile strength was measured to be in the range of 184–220 MPa, which corresponds to 60–72% joint efficiency. Digital image correlation analysis of the strain development during tensile testing revealed that root cracks formed, before the final fracture ran close to the aluminium-steel interface. A significant amount of residual aluminium was found on the steel fracture surface, especially in regions that experienced higher pressure during joining. Scanning and transmission electron microscopy revealed that the bond strength could be attributed to a combination of microscale mechanical interlocking and a discontinuous nanoscale interfacial Al-Fe-Si intermetallic phase layer. Analysis of scanning electron diffraction data acquired in a tilt series, indicated that the polycrystalline intermetallic phase layer contained the cubic αc phase. The results give insight into the bonding mechanisms of aluminium-steel joints and into the performance of HYB joints, which may be used to better understand and further develop aluminium-steel joining processes.

Journal Keywords: Aluminium-steel joining; Hybrid metal extrusion & bonding; Al-Fe-Si intermetallic phases; Transmission electron microscopy; Scanning electron diffraction

Diamond Keywords: Alloys

Subject Areas: Materials, Engineering

Diamond Offline Facilities: Electron Physical Sciences Imaging Centre (ePSIC)
Instruments: E02-JEM ARM 300CF

Added On: 18/11/2020 10:05


Discipline Tags:

Automotive Materials Science Engineering & Technology Metallurgy

Technical Tags:

Microscopy Electron Microscopy (EM) Transmission Electron Microscopy (TEM) Scanning Transmission Electron Microscopy (STEM)