Attempt to depict glass forming ability of bulk metallic glasses using the criterion of the total relaxation time at the glass transition Jing Guo a,b , Fang-Qiu Zu a, * , Zhi-Hao Chen a , Xian-Fen Li a , Yun Xi a , Rong-Rong Shen a , Yan Zhang a a College of Materials Science and Engineering, Hefei University of Technology, Hefei 230009, People’s Republic of China b The Key Laboratory of Liquid Structure and Heredity of Materials, Ministry of Education, Shandong University, Jinan 250061, China Received 27 September 2005; received in revised form 10 May 2006 Available online 28 August 2006 Abstract The relationship between the total relaxation time at the glass transition s tot T g and Glass Forming Ability (GFA) of Bulk Metallic Glasses (BMG) has been discussed. Subsequently s tot T g is applied to estimate the GFA of Zr 52.5 Al 10 Ni 14.6 Cu 17.9 Ti 5 and Zr 57 Al 10 Ni 12.6 - Cu 15.4 Nb 5 BMGs. The result indicates that the GFA of the former is greater than that of the latter, which is also demonstrated by the widely accepted criteria of both supercooled liquid region DT x and reduced glass transition temperature T rg . That testifies the relax- ation time of glass transition (s tot T g ) is feasible for depicting GFA of BMGs. As a criterion estimating GFA, s tot T g could be easily obtained in practice, and then the occurrence of this criterion will promote exploring new bulk glassy composition. In addition, when s tot T g and DT x are calculated, the characteristic temperatures are determined by a electrical resistivity method besides DSC method. The values obtained from electrical resistivity method agree well with those from DSC method, which proves that the electrical resistivity method is applicable for determining the characteristic temperatures of BMGs. Ó 2006 Elsevier B.V. All rights reserved. PACS: 61.43.Dq; 65.50.+m; 81.05.Kf Keywords: Glass transition; Metallic glasses 1. Introduction During the last few decades, a lot of effort has been made in trying to search the new systems of BMGs [1–3], most of which is focused on the study of glass forming abil- ities (GFA) of BMGs. Up to now, some characteristic parameters have been used to describe GFA of different alloys. Among them the critical cooling rate R c , defined as the cooling rate that is tangential to the ‘nose’ of the continuous–cooling–transition (CCT) curve, is a very direct and tangible one, but it is not convenient in practice, because it is hard to be measured precisely in the actual cooling process due to many uncertainties, such as temper- ature changing, heterogeneous nucleation, etc. So some indirect parameters such as reduced glass transition tem- perature T rg [4–6] and interval of supercooled liquid region DT x [7–10] were introduced to estimate the glass forming abilities of various alloy systems. T rg is defined most fre- quently as T g /T m ratios (T g : glass transition temperature, T m : melting point) and Turnbull [11] proposed that for a given composition the glass forming tendency should increase with the reduced glass transition temperature. But in the Ref. [12,13], it was found that the values of T rg based on T g /T m do not reflect the differences in the GFA among some bulk metallic forming alloys which have a range of critical cooling rates for glass forming. The tem- perature interval (DT x ) of the supercooled liquid region, 0022-3093/$ - see front matter Ó 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.jnoncrysol.2006.06.035 * Corresponding author. Tel.: +86 0551 2905057. E-mail address: fangqiuzu@hotmail.com (F.-Q. Zu). www.elsevier.com/locate/jnoncrysol Journal of Non-Crystalline Solids 352 (2006) 3859–3863