Cooperative Shear in Bulk Metallic Glass Composites Containing Metastable β-Ti Dendrites

Area of Science:

• Materials Science
• Metallurgy
• Solid Mechanics

Background:

• Bulk metallic glass composites (BMGCs) are advanced materials with potential applications in structural components.
• Understanding the plastic deformation mechanisms of BMGCs is crucial for optimizing their mechanical properties and performance.
• Metastable β-Ti dendrites within BMGCs can influence their deformation behavior.

Purpose of the Study:

• To investigate and elucidate a novel plastic deformation mechanism in bulk metallic glass composites (BMGCs) containing metastable β-Ti dendrites.
• To characterize the cooperative shear events that mediate plastic deformation beyond the ultimate tensile strength.
• To understand the formation and role of ω-Ti bands in the deformation process.

Main Methods:

• Microstructural analysis of BMGCs subjected to tensile testing.
• High-resolution imaging to observe shear band formation and ω-Ti band characteristics.
• Analysis of local strain rates during deformation events.

Main Results:

• A novel plastic deformation mechanism involving cooperative shear events was identified in BMGCs with β-Ti dendrites.
• Cooperative shear comprises a shear band in the glassy matrix and a continuous ω-Ti band (∼10 nm thick) within the β-Ti dendrite.
• This mechanism leads to serrated shear avalanches and is driven by high local strain rates, causing narrow ω-Ti band formation.

Conclusions:

• The cooperative shear mechanism represents a significant enrichment of the known deformation behaviors in BMGCs.
• This study provides deeper insights into the formation mechanisms of ω-Ti within the context of plastic deformation.
• The findings contribute to a more comprehensive understanding of the mechanical response of metallic glass composites.