Crystallization and mechanical behavior of (Hf, Zr)–Ti–Cu–Ni–Al metallic glasses X. Gu a, * , T. Jiao b , L.J. Kecskes c , R.H. Woodman c , C. Fan a , K.T. Ramesh b , T.C. Hufnagel a a Department of Materials Science and Engineering, Johns Hopkins University, Maryland Hall 102, 3400 North Charles Street, Baltimore, MD 21218, USA b Department of Mechanical Engineering, Johns Hopkins University, Maryland Hall 102, 3400 North Charles Street, Baltimore, MD 21218, USA c US Army Research Laboratory, Aberdeen Proving Ground, MD 21005, USA Abstract We have prepared a series of glass-forming alloys of composition (Hf x Zr 1x ) 52:5 Cu 17:9 Ni 14:6 Al 10 Ti 5 and (Hf x Zr 1x ) 57 Cu 20 Ni 8 Al 10 Ti 5 with x ¼ 0–1. The substitution of Hf for Zr reduces the glass-forming ability of these alloys; while all compositions of (Hf x Zr 1x ) 52:5 Cu 17:9 Ni 14:6 Al 10 Ti 5 can be cast in bulk form, amorphous samples of the Hf-rich compositions (x > 0:8) of (Hf x Zr 1x ) 57 Cu 20 Ni 8 Al 10 Ti 5 can only be produced by rapid solidification. The alloys show similar crystallization behavior, although we observe an intermediate phase in the Hf-rich glasses (Al 16 Hf 6 Ni 7 ) that is not observed in the Zr-rich glasses. The YoungÕs modulus and the flow strength under quasi-static uniaxial compression increase linearly with increasing Hf content. Under dynamic loading, the failure strength of all of the alloys tested decreases with increasing strain rate. The differences in mechanical behavior between the Zr- and Hf-rich glasses can be rationalized in terms of the higher melting point of Hf. The addition of Hf increases the average bond energy of the alloy, resulting in a higher modulus and increasing the activation energy for atomic motion by which plastic defor- mation occurs. Ó 2003 Elsevier Science B.V. All rights reserved. PACS: 61.43.Dq; 62.20.Dc; 81.05.Kf; 81.70.Pg 1. Introduction Multi-component Zr-based bulk metallic glas- ses have been widely investigated [1–3]. These al- loys can be prepared at low cooling rates (below 10 3 K/s) and usually have wide supercooled re- gions (as large as 50 K). Plastic deformation of bulk metallic glasses is controlled predominantly by shear localization [4,5]. As a result, they usually exhibit very limited overall plasticity, which re- stricts most engineering applications of bulk me- tallic glasses as a structural material. However, shear localization leads to self-sharpening behav- ior during dynamic impact, which is important for making efficient anti-armor penetrators [6,7]. To * Corresponding author. Tel.: +1-410 516 0462; fax: +1-410 516 5293. E-mail address: xgu@jhu.edu (X. Gu). 0022-3093/03/$ - see front matter Ó 2003 Elsevier Science B.V. All rights reserved. doi:10.1016/S0022-3093(02)01990-7 Journal of Non-Crystalline Solids 317 (2003) 112–117 www.elsevier.com/locate/jnoncrysol