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Part A: Materials Science

Effect of microstructure on fracture in age hardenable Al alloys

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Pages 1476-1498 | Received 05 Aug 2019, Accepted 28 Jan 2020, Published online: 17 Feb 2020
 

ABSTRACT

In the present study, the fracture behaviour of AA6016 alloy was investigated during bending deformation. Wrap-bend tests were conducted and the material was subjected to different bend angles to study crack propagation. The average grain size of the as-received material is approximately 45 μm. The aspect ratio of the grains was changed from 0.53 to 0.40 during bending. The presence of deformation bands was observed during bending in both tensile and compressive regions of the sample. No orientation correlation was observed between the deformation band and its corresponding parent grain. The Schmid factor inside the deformation bands was higher than that of the parent grain, which indicates that the deformation bands accommodate strain during bending. The crystallographic texture evolved significantly during bending deformation. The strength of cube texture component decreases with increasing bend angle and new texture components formed during bending. These new texture components favour either single slip or duplex slip. A mixture of intra-granular and inter-granular fracture occurs during bending. It is observed that inter-granular crack propagation is predominantly favoured along high-angle boundaries, and grain boundary de-cohesion occurs in regions where the misorientation angle is greater than 40°. The formation of deformation-induced coincidence lattice site (CSL) boundaries is also observed during bending and it is shown that the volume fraction of CSL boundaries of Σ3 type increases with increasing bend angle. The current study shows that the formation of deformation-induced CSL boundaries of Σ3 type in AA6016 alloy can improve its inherent resistance to crack propagation during bending.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

The authors are thankful to Natural Sciences and Engineering Research Council of Canada [grant no APCPJ 441668-12], the Engineering Research Council – Industrial Research Chair (NSERC-IRC) [grant no IRCPJ-503185-2016], CanmetMATERIALS, Natural Resources Canada, General Motors of Canada and Hydro Aluminium Rolled Products GmbH, Germany for supporting this work.

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