Designing metallic glass matrix composites with high toughness and tensile ductility

• Published in: Nature (London) Vol. 451; no. 7182; pp. 1085 - 1089
• Main Authors: Duan, Gang, Lind, Mary-Laura, Wiest, Aaron, Demetriou, Marios D, Johnson, William L, Suh, Jin-Yoo, Hofmann, Douglas C
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 28.02.2008; Nature Publishing; Nature Publishing Group
• Subjects: Alloys; Composite materials; Condensed matter: structure, mechanical and thermal properties; Deformation; Deformation and plasticity (including yield, ductility, and superplasticity); Dendrites; Ductility; Exact sciences and technology; Humanities and Social Sciences; letter; Materials science; Mechanical and acoustical properties of condensed matter; Mechanical properties of solids; multidisciplinary; Optimization; Physics; Plasticity; Science; Science (multidisciplinary); Strain; Structural engineering; Tension; Titanium; Zirconium; Metallic glasses; Transmission electron microscopy; Ductility; Mechanical strength; Plasticity; Elasticity; Microstructure; Shear band; Optimization; Fracture toughness
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/nature06598

The selection and design of modern high-performance structural engineering materials is driven by optimizing combinations of mechanical properties such as strength, ductility, toughness, elasticity and requirements for predictable and graceful (non-catastrophic) failure in service. Highly processable bulk metallic glasses (BMGs) are a new class of engineering materials and have attracted significant technological interest. Although many BMGs exhibit high strength and show substantial fracture toughness, they lack ductility and fail in an apparently brittle manner in unconstrained loading geometries. For instance, some BMGs exhibit significant plastic deformation in compression or bending tests, but all exhibit negligible plasticity (<0.5% strain) in uniaxial tension. To overcome brittle failure in tension, BMG-matrix composites have been introduced. The inhomogeneous microstructure with isolated dendrites in a BMG matrix stabilizes the glass against the catastrophic failure associated with unlimited extension of a shear band and results in enhanced global plasticity and more graceful failure. Tensile strengths of ∼1 GPa, tensile ductility of ∼2-3 per cent, and an enhanced mode I fracture toughness of K1C  40 MPa m1/2 were reported. Building on this approach, we have developed 'designed composites' by matching fundamental mechanical and microstructural length scales. Here, we report titanium-zirconium-based BMG composites with room-temperature tensile ductility exceeding 10 per cent, yield strengths of 1.2-1.5 GPa, K1C up to ∼170 MPa m1/2, and fracture energies for crack propagation as high as G1C   340 kJ m-2. The K1C and G1C values equal or surpass those achievable in the toughest titanium or steel alloys, placing BMG composites among the toughest known materials.