Twinning mediated anisotropic fracture behavior in bioimplant grade hot-rolled pure magnesium

Bioimplant grade hot-rolled magnesium with equiaxed microstructure and basal texture was examined for fracture toughness (FT) anisotropy using fatigue pre-cracked single-edge notch bending specimens with the notch, an , perpendicular to and 45 degrees to rolling direction (RD). Due to adequate crack-tip plasticity, the size-independent elastic-plastic fracture toughness ( JIc ) were determined. Anisotropic JIc was observed due to different twin lamellae formation w.r.t. notch owing to the initial basal texture with {1010 } and {1120 } poles mostly and perpendicular to to RD. The out-of-plane tensile stresses activated the {1012 }1011 extension twins (ET) as usual with matrix-ET E15b coincident site lattice boundary (CSLB) interfaces. While the in-plane tensile stress perpendicular to to the crack-tip activated {1011 }1012 contraction twins (CT) that transform into {1011 } - {1012 } double twins (DT) with matrix-DT E23b and E15a CSLBs. For an RD, large DT lamellae fraction formed at similar to 30 degrees and few ETs at similar to 30 degrees and similar to 90 degrees to the notch with crack growth mainly via the E23b/ E15a CSLB interfaces during FT. While, significant DT and ET lamellae developed at similar to 0 degrees and similar to 60 degrees with cracking via the matrix-DT E23b/ E15a and matrix-ET E15b CSLBs for an perpendicular to RD. The DT and ET lamellae activated at similar to 15 degrees, and the crack propagated through E15b for an similar to 45 degrees to RD. The JIc and the crack-tip plastic zone decreases, while the elastic component of the J-integral ( Jel ) and the ET formation increases from an , perpendicular to , to similar to 45 degrees to RD. The strain incompatibility of matrices was higher with the geometrically hard ETs than DTs. Thus, brittle interlamellar cracking occurred through the E15b interfaces. In contrast, almost similar and higher crack-tip plasticity occurred in matrix and DT domains during crack propagation via E23b/ E15a CSLBs. Crack growth through E23b/ E15a led to high JIc , both E15b and E23b/ E15a led to moderate JIc , and E15b least (c) 2024 Chongqing University. Publishing services provided by Elsevier B.V. on behalf of KeAi Communications Co. Ltd. This is an open access article under the CC BY-NC-ND license ( http://creativecommons.org/licenses/by-nc-nd/4.0/ ) Peer review under responsibility of Chongqing University