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MM: Fachverband Metall- und Materialphysik

MM 33: Topical Session: Fundamentals of Fracture – Amorphous Metals

MM 33.3: Talk

Wednesday, March 29, 2023, 16:15–16:30, SCH A 215

Microscale fracture behavior of Laves phases in the Mg-Ca-Al ternary alloy system — •Anwesha Kanjilal, Uzair Rehman, James P. Best, and Gerhard Dehm — Max-Planck-Institut für Eisenforschung GmbH, Düsseldorf, Germany

Brittle intermetallic Laves phases often act as preferential sites for defects such as cracks in the Mg-Ca-Al alloys. This study investigates the nano- and microscale fracture behavior of C15 Al2Ca and C14 Mg2Ca Laves phases prepared as single-phase specimens. Spherical nanoindentation was performed at room temperature in grains of varying surface orientation to identify cleavage planes and orientation effects. Post mortem microscopic examination using electron channeling contrast imaging revealed cracks around indents in both Laves phases, and together with electron backscatter diffraction low index crack planes were identified using trace analyses. For C15 phase, further microcantilever bending and micropillar splitting geometries were fabricated using focused ion beam methodology, wherein fracture toughness Kc ~1-2 MPam^0.5 was obtained from in-situ testing. Fast screening methodology based on in-situ scratch and nanoindentation at temperatures from 25 to 500 °C was employed to determine brittle-to-ductile transitions in the Laves phases. The morphology of slip lines and cracks, and decrease in hardness during nanoindentation suggests probable transition ~0.5Tm for C15 phase, while studies on C14 are ongoing.

The authors gratefully acknowledge the financial support of Deutsche Forschungsgemeinschaft (DFG) within project B06 of Collaborative Research Center (SFB) 1394, project number 409476157.