Novel microstructure and properties of multicomponent CoCrCuFeNiTi x alloys X.F. Wang, Y. Zhang * , Y. Qiao, G.L. Chen State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, XueYuan Road 30#, Haidian District, Beijing 100083, China Received 10 May 2006; received in revised form 7 July 2006; accepted 4 August 2006 Available online 5 October 2006 Abstract CoCrCuFeNiTi x (x values in molar ratio, x ¼ 0, 0.5, 0.8 and 1.0) were prepared by arc melting of the pure elements and suction casting under an argon atmosphere. Both CoCrCuFeNi and CoCrCuFeNiTi 0.5 alloys form a single FCC solid solution. While the alloys of CoCrCuFeNiTi 0.8 and CoCrCuFeNiTi are basically composed of primary FCC solid solution and eutectic mixture of FCC phase and Laves phase of Fe 2 Ti type. The yield strength of the alloys increases from 230 MPa to 1272 MPa with the increase of Ti addition, among which the CoCrCuFeNiTi 0.5 alloy, especially, exhibits compressive strength of up to 1650 MPa together with extensive work hardening and large plastic strain limit of 22%. An interesting tran- sition from paramagnetism to superparamagnetism has been discovered due to the appearance of nanoparticles embedded in the amorphous phase. Ó 2006 Elsevier Ltd. All rights reserved. Keywords: B. Magnetic properties; B. Mechanical properties at ambient temperature; C. Casting; D. Microstructure 1. Introduction Conventional strategy for developing metallic alloys is to select one or two elements as the main components based on a primary property requirement, and to use alloying addi- tions to confer secondary properties [1], such as iron-, cop- per-, and aluminum-based alloys [2,3] or the intermetallic compounds of TieAl, NieAl and FeeAl binary systems which appeared in the 1970s because of their extremely high specific strengths and thermal resistance [4]. In the last two de- cades, multicomponent bulk amorphous alloys have attracted great attentions because they exhibit unique properties com- pared to its counterpart crystalline materials, e.g. 2e3 times of fracture strength of crystalline materials, high elastic strain limit and high corrosion resistance [5e9]. However, the design concept of multicomponent bulk amorphous alloys was, once again, based on one principal element [10]. Conventional alloy development strategy leads to an enormous amount of knowl- edge about alloys based on one or two main components, but to very little or no knowledge about multiprincipal elements system. Actually, for quaternary, quinary and higher order sys- tems, information about alloys in the center of the phase dia- gram is non-existent [1]. The main reason for not incorporating multiprincipal elements is the anticipated forma- tion of many intermetallic compounds and complex micro- structures. However, it has been reported that a quinary alloy Fe 20 Cr 20 Mn 20 Ni 20 Co 20 [1] and the Al x CoCrCuFeNi alloys with minor aluminum addition [10] form a single FCC solid solution, as well with promising mechanical properties that may have potential for the requirements of high temperature alloys [11]. Just based on the simple structure and unique properties, there has been increasing interests for exploring the equiatomic multicomponent alloy series. In this paper, a novel series of CoCrCuFeNiTi x (x values in molar ratio, x ¼ 0, 0.5, 0.8 and 1.0) alloys were prepared by well-developed arc melting and casting method. Their micro- structure and mechanical properties were examined, further- more, we described an initial attempt to investigate the * Corresponding author. Tel.: þ86 010 62322160; fax: þ86 010 62332508. E-mail address: drzhangy@skl.ustb.edu.cn (Y. Zhang). 0966-9795/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.intermet.2006.08.005 Intermetallics 15 (2007) 357e362 www.elsevier.com/locate/intermet