In-Situ Study on the Tensile Deformation and Fracture Mechanism of a Bimodal-Structured Mg-Gd-Y Alloy

• Published in: Materials Vol. 16; no. 17; p. 5978
• Main Authors: Ning, Jiangli, Gao, Bosong, Zhou, Jialiao, Chen, Liansheng, Tang, Guangze, Li, Shubo
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 31.08.2023; MDPI
• Subjects: Alloys; bimodal structure; Crack initiation; Deformation; Ductility; Fracture mechanics; fracture mechanism; Fractures; Gadolinium; Grain boundaries; Grain size; Hot working; in-situ tensile test; Incompatibility; Magnesium alloys; Magnesium base alloys; Mechanical properties; Mg-RE alloy; Microcracks; Nucleation; Precipitation hardening; slip behavior; Software; Specialty metals industry; Strain hardening; Stress concentration; Stress propagation; Tensile deformation; China
• ISSN: 1996-1944; 1996-1944
• DOI: 10.3390/ma16175978

The as-extruded (EX) Mg-Gd-Y alloy studied here exhibited a bimodal structure, composed of fine dynamic recrystallized (DRXed) grains with random orientations and longitudinal coarse hot-worked grains. The slip analysis showed the DRXed grains exhibited mainly basal slips, while the hot-worked grains exhibited mainly prismatic slips during the tensile deformation. The distribution of geometrically necessary dislocations (GNDs) showed that there was strain partitioning between the fine and coarse grain regions. The hetero-deformation induced (HDI) hardening occurred between the two domains. It improves the strength and strain hardening capability of the alloy, leading to good strength-ductility synergy. Microcracks tended to nucleate at the DRXed grain boundaries, as well as at the interface between the two domains. The calculation of geometric compatibility parameter (m’) indicated that strain incompatibility between the adjacent grains induced the crack nucleation. The toughening effect of the fine DRXed grains hindered the crack propagation. However, the major crack formed at the interface between the two domains propagated unstably, due to the high stress concentration and the large crack size, causing the final failure.