Shape Memory Bulk Metallic Glass Composites

Glass-forming and shape memory metals may provide a route to fabricating materials with enhanced mechanical properties. Bulk metallic glasses (BMGs) are being studied extensively as potential structural materials as they have a unique array of mechanical properties compared to traditional crystalline metals (1–4). Their amorphous microstructure and variable composition give BMGs ultrahigh-yield strengths, large elastic strain limits, high hardness, corrosion resistance, and the ability to be processed like a plastic. So far, however, BMGs have not found many structural applications because of their catastrophic failure under tension (tensile loading) and their typically low fracture toughness (resistance to cracking), both resulting from the same amorphous microstructure that differentiates them from crystalline metals. This shortcoming has been addressed in recent years with the development of BMG matrix composites (BMGMCs)—two-phase alloys consisting of soft, crystalline dendrites grown in situ in a glass-forming matrix (5–9). When designed and processed properly, BMGMCs retain the positive structural features exhibited by monolithic (single-phase) BMGs, but can also exhibit enhanced tensile ductility, fracture toughness, and fatigue endurance, which makes them desirable as engineering materials (5, 10, 11).

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