Superplasticity and superplastic forming ability of a Zr–Ti–Ni–Cu–Be bulk metallic glass in the supercooled liquid region G. Wang a,b , J. Shen a, * , J.F. Sun a , Y.J. Huang a , J. Zou c , Z.P. Lu d , Z.H. Stachurski b , B.D. Zhou a a School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001, China b Department of Engineering, FEIT, Australian National University, ACT 0200, Australia c School of Engineering and Center for Microscopy and Microanalysis, University of Queensland, QLD 4066, Australia d Metals and Ceramic Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6115, USA Received 25 July 2004; received in revised form 29 October 2004 Available online 21 December 2004 Abstract The superplastic deformation behavior and superplastic forming ability of the Zr 41.25 Ti 13.75 Ni 10 Cu 12.5 Be 22.5 (at.%) bulk metallic glass (BMG) in the supercooled liquid region were investigated. The isothermal tensile results indicate that the BMG exhibits a New- tonian behavior at low strain rates but a non-Newtonian behavior at high-strain rates in the initial deformation stage. The maximum elongation reaches as high as 1624% at 656 K, and nanocrystallization was found to occur during the deformation process. Based on the analysis on tensile deformation, a gear-like micropart is successfully die-forged via a superplastic forging process, demonstrating that the BMG has excellent workability in the supercooled liquid region. Ó 2004 Elsevier B.V. All rights reserved. PACS: 61.43.D; 62.20.F; 61.72; 81.20.H 1. Introduction As a kind of material containing no crystallographic defects, bulk metallic glasses (BMGs) have many poten- tial engineering applications resulting from their excel- lent properties including high strength, low elastic modulus and high wear resistance [1–4]. In addition, BMGs usually exhibit a drastic reduction in viscosity in the supercooled liquid region, DT, defined as the tem- perature interval between the glass transition tempera- ture T g and the onset crystallization temperature T x [5,6]. Therefore, due to their superplastic deformation ability in this temperature range [6–13], BMGs are capa- ble of being fabricated into near-net-shape components, particularly the mircocomponents with irregular shapes. For example, several Zr-, Pd-, La-based BMGs have been used to manufacture the microcomponents for micro electro-mechanical systems (MEMS) [14–18]. The microstructural evolutions, including phase separa- tion and nanocrystallization, are always activated due to the influence of either applied stress or environmental heat during the superplastic deformation process [8,9,11–13]. These changes usually destruct the isotropic homogeneity and worsen the mechanical properties of BMGs, which is unfavorable for manufacturing micro- components [15]. The purpose of the present study is to investigate the superplastic flow behavior and the effect of microstructural evolutions on the flow behavior of the Zr 41.25 Ti 13.75 Ni 10 Cu 12.5 Be 22.5 BMG during tensile deformation in the superpcooled liquid region. In the light of the superplastic deformation behavior observed in the present study, a gear-like BMG micropart has 0022-3093/$ - see front matter Ó 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.jnoncrysol.2004.11.006 * Corresponding author. Tel.: +86 451 8641 4797; fax: +86 451 8641 5776. E-mail address: junshen@public.hr.hl.cn (J. Shen). www.elsevier.com/locate/jnoncrysol Journal of Non-Crystalline Solids 351 (2005) 209–217