Effect of Grain Boundaries on Fracture Toughness in Ultrafine-Grained Metals by Atomic-Scale Computational Experiments

Abstract:

In order to investigate roles of grain boundaries on the improved fracture tough-ness in ultrafine-grained metals, interactions between crack tips, dislocations, and disclinationdipoles at grain boundaries are performed to aluminium bicrystal models containing a crackand h112i tilt grain boundaries using molecular dynamics simulations. A proposed mechanismto express the improved fracture toughness in ultrafine-grained metals is the disclination shield-ing effect on the crack tip mechanical field. The disclination shielding can be activated whena transition of dislocation sources from crack tips to grain boundaries and a transition of thegrain boundary structure into a neighbouring energetically stable boundary by emitting dis-locations from the grain boundary occur. The disclination shielding effect becomes large asdislocations are continuously emitted from the grain boundary without dislocation emissionsfrom crack tips. This mechanism can further shield the mechanical field around the crack tipand obtain the plastic deformation by dislocation emissions from grain boundaries, hence itcan be expected that the disclination shielding effect can improve the fracture toughness inultrafine-grained metals

• Periodical: Materials Science Forum (Volumes 706-709)
• Pages: 1841-1846
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.706-709.1841
• Online since: January 2012
• Authors: Tomotsugu Shimokawa, Masaki Tanaka, Kenji Higashida
• Keywords: Crack Tip Shielding, Disclination, Dislocation, Fracture Toughness, Grain Boundary, Molecular Dynamic (MD), Ultrafine-Grained Metal

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