Fracture toughness in direct extruded Mg–Al–Zn alloys

• Published in: Journal of materials research Vol. 22; no. 9; pp. 2598 - 2607
• Main Authors: Somekawa, Hidetoshi, Kim, Han S., Singh, Alok, Mukai, Toshiji
• Format: Book Review Journal Article
• Language: English
• Published: New York, USA Cambridge University Press 01-09-2007
• Subjects: Extrusion; Toughness; Extrusion; Toughness; Mg
• ISSN: 0884-2914; 2044-5326
• DOI: 10.1557/jmr.2007.0334

Fracture toughness and its deformed structures were investigated on a Mg–3Al–1Zn (AZ31) alloy processed by direct extrusion. The average grain sizes of the alloy after extrusion at temperatures of 473 and 573 K were 4.0 and 14.5 μm, respectively (i.e., fine-grained and coarse-grained alloys). The plane-strain fracture toughness, KIC, as determined by stretched zone analysis in fine-grained and coarse-grained alloys was estimated to be 24.9 and 22.7 MPam1/2, respectively. Microstructural observations of the fine-grained alloy after fracture toughness testing showed that non-basal slip and grain-boundary sliding was activated even at room temperature. In addition, the {10-12} deformation twins were observed despite the fine-grained structures. However, the fraction of deformation twins was reduced with grain refinement, which related to the enhancement of fracture toughness with grain refinement.