Ti-based metallic glasses and nanostructured materials
Our research aims to expand the range and performance of metallic glasses and nanostructured alloys in different structural applications. Metals typically take on an ordered, crystal-like atomic structure. The glassy state is reached when a cooled liquid solidifies without crystallization, which is associated with the phenomena of the glass transition. By avoiding crystallization, the material keeps its amorphous (glassy) structure at room temperature that leads to unique combination of properties. With well-designed compositions it is now possible to cast liquid alloys into the glassy state in the bulk (cm-sized cross-sections) via conventional metal processing such as casting.
Designing biocompatible Ti-based metallic glasses for implant applications
A major problem facing the development of biocompatible metallic glasses is the one of inducing amorphization without using any harmful alloying additions. In the present paper we developed new ultra-hard and corrosion-resistant Ti-based metallic glasses and nano-phase composites, free of toxic elements Ni and Cu. We studied the glass-formation and thermal stability of Ti75Zr10Si15 and Ti60Nb15Zr10Si15 alloys and performed a preliminary evaluation of their corrosion and mechanical behavior, which is essential in assessing their suitability for biomedical applications.
M. Calin, A. Gebert, A.C. Ghinea, P.F. Gostin, S. Abdi, C. Mickel, J. Eckert, Mater. Sci. Eng. C 33 (2013) 875-883 doi:10.1016/j.msec.2012.11.015 URL
Design of ductile bulk metallic glasses by adding “soft” atoms
Mechanical properties are a focus for the current high interest in metallic glasses. We propose a strategy for the design of ductile bulk metallic glasses (BMGs) through minor substitution using relatively large atoms (Indium), which make the bonding nature become more metallic and with it less shear resistant. Such a locally modified structure results in topological heterogeneity, which appears to be crucial for achieving enhanced plasticity. This strategy is verified for Ti-Zr-Cu-Pd glassy alloys, in which Cu was replaced by indium (In), and seems to be extendable to other BMG systems.
N. Zheng, R. T. Qu, S. Pauly, M. Calin, T. Gemming, Z. F. Zhang, J. Eckert, Applied Physics Letter 100 (2012) 141901 URL
Metallic glasses: Notch-insensitive materials
The notch tensile behavior of bulk metallic glasses (BMGs) is investigated and compared with that of crystalline metals and ceramics. It is found that the tensile strength of the studied BMGs is insensitive to notches, and much better than that of conventional brittle materials. Moreover, notched BMGs exhibit enhanced plastic deformation ability with the formation of shear band zones, which is distinctively different from traditional metals and ceramics, while it is consistent with the nearly zero tensile plastic elongation but high toughness of BMGs.
R.T. Qu, M. Calin, J. Eckert, Z.F. Zhang, Scripta Materialia 66 (2012) 733-736 URL
In situ high-energy X-ray diffraction observation of structural evolution in a Ti-based bulk metallic glass upon heating
Annealing is an effective way to obtain the nano-phase composites through partial crystallization of BMGs. In addition, the thermoplastic forming of BMGs in the supercooled liquid region required the understanding of structural evolutions upon heating, which significantly influence their formability. In the present paper we studied the structural evolution (relaxation and crystallization) of the Ti40Zr10Cu34Pd14Sn2 bulk metallic glass upon controlled heating by means of in situ high-energy X-ray diffraction (synchrotron-based experiments).
N. Zheng, G. Wang, L.C. Zhang, M. Calin, M. Stoica, G. Vaughan, N. Mattern, J. Eckert, Journal of Materials Research 25 (2010) 2271-2277 URL
Tailoring of microstructure and mechanical properties of a Ti-based bulk metallic glass-forming alloy
Lightweight Ti-based bulk amorphous structural metals exhibit more than double the specific strength of conventional titanium alloys. However, they generally lack ductility and fail in a macroscopically brittle manner in unconstrained loading geometries. To achieve plasticity of Ti-based bulk metallic glasses without sacrificing their high strength, the microstructure of Ti50Cu20Ni24Sn3Si2B1 alloy was tailored to form in situ glassy-matrix composites. Structural characteristics and mechanical properties of these glassy materials were studied and are presented.
M. Calin, L.C. Zhang, J. Eckert, Scripta Materialia 57 (2007) 1101-1104 URL