Resonant vibration analysis for temperature dependence of elastic properties of bulk metallic glass
- PDF / 139,480 Bytes
- 5 Pages / 585 x 783 pts Page_size
- 48 Downloads / 195 Views
Sixto Giménezb) Department of Metallurgy and Materials Engineering (MTM), Katholieke Universiteit Leuven, B-3001 Heverlee, Belgium
Jan Schroersc) Liquidmetal Technologies, Lake Forest, California 92630 (Received 16 June 2006; accepted 30 October 2006)
The variation of a Zr57Nb5Cu15Ni13Al10 bulk metallic glass’s elastic constants with temperature and thermal history was investigated, using an impulse excitation technique for resonant vibration analysis. The Young’s modulus at 550 K is 78 GPa with a slope of −17 MPa/K in the glass as-produced and increases to 80 GPa with a slope of −26 MPa/K upon annealing. The modulus of the supercooled liquid at 700 K is 74 GPa with a slope of −90 MPa/K, whereas for the crystallized material E ⳱ 100 GPa with a slope of −15 MPa/K. These results are interpreted in terms of the vibrational and configurational contributions to the temperature dependence and compared with calorimetry data. I. INTRODUCTION
Fundamental questions about the nature of the glassy state and the deformation behavior of amorphous metals have recently been looked at in a new light, based on correlations of various properties with elastic constants.1 For example, fragility of glass-forming liquids was found to correlate with Poisson’s ratio,2 and toughness of metallic glasses was shown to be related to the ratio of the shear modulus to the bulk modulus,3,4 even when a glass is embrittled by annealing treatments. The scaling parameter for the barrier height in the cooperative shear model from which Johnson and Samwer derived a universal yield criterion for metallic glasses,5 is the shear modulus. In this cooperative shear model, the temperature dependence of the shear modulus governs the temperature dependence of the viscosity, i.e., the fragility of the liquid.6 It is therefore timely and important to acquire experimental results on the dependence of the elastic constants of bulk metallic glasses on temperature and annealing condition,7 especially near the glass transition. Determining elastic constants of a material precisely and accurately by mechanical testing can be difficult, a)
Address all correspondence to this author. e-mail: [email protected] b) Present address: Centro de Estudios e Investigaciones Técnicas (CEIT) de Gipuzkoa, 20018 San Sebastán, Spain. c) Department of Mechanical Engineering, Yale University, New Haven, Connecticut 06511. DOI: 10.1557/JMR.2007.0065 J. Mater. Res., Vol. 22, No. 2, Feb 2007
http://journals.cambridge.org
Downloaded: 02 Apr 2015
especially at elevated temperatures. These data, and the trends in these data with changes in temperature and annealing condition, are nevertheless important for accurate models of the deformation behavior of metallic glasses and may be important for understanding shear localization even at room temperature. Indirect measurements, where the elastic properties are calculated from sound velocity or from vibration frequencies, are precise and reproducible; their accuracy is limited mainly by the accuracy of the sample dimensions. The impulse
Data Loading...
