Journal of Alloys and Compounds 390 (2005) 82–87 Effects of ternary alloying on mechano-synthesis and nano-crystal stability of an iron-silicon alloy B. Zuo, T. Sritharan ∗ , Y.B. Teo, M. Damayanti School of Materials Engineering, Nanyang Technological University, Nanyang Avenue, Singapore 639798, Singapore Received 30 July 2004; received in revised form 17 August 2004; accepted 18 August 2004 Abstract This paper reports the effects of ternary alloying additions Al, Cu and Nb to Fe 75 Si 25 in high energy ball milling to produce nano-crystalline alloy powder, and its microstructural stability during subsequent high temperature annealing. It is shown that all additions generally retard grain growth up to some temperature. Nb appears to amorphise the alloy. The binary base alloy and Al containing alloy forms the DO 3 ordered structure at high temperatures accompanied by rapid grain growth. The Cu and Nb containing alloys precipitate Cu and Nb 2 Fe at high temperatures but do not become ordered. © 2004 Elsevier B.V. All rights reserved. Keywords: Nanostructures; Amorphisation; High-energy ball milling 1. Introduction Nano-crystalline (NC) soft magnetic materials show higher permeability and lower coercivity compared to their microcrystalline counterparts because their grain size is smaller than the ferromagnetic exchange length [1,2]. How- ever, it is not easy to produce bulk magnetic materials in NC form by conventional metal processing techniques. One op- tion the industry uses is to form an amorphous ribbon by rapid solidification, and then control-anneal to nucleate the nano-crystals of a specific phase [3]. Another is to mechano- synthesise in a high-energy ball mill to produce NC alloy powders from the elemental powders [4]. The ball milling process leaves the powder in a state of internal strain and thus stress relaxation by annealing is a necessary processing step. Further, a solid piece of a particular shape is frequently required in applications, which means some high temperature exposure may be inevitable. Thus, a resistance to grain coars- ening during high temperature exposures will be an asset to any NC material to preserve the advantageous properties. ∗ Corresponding author. E-mail address: assritharan@ntu.edu.sg (T. Sritharan). When designing alloys, one must take into account both the processing and the service requirements. This is practiced in the design of magnetic alloys for rapid solidification, where specific alloying elements are added to aid the amorphisation during solidification [5], and some others are added for nucle- ation of the nano-crystals during subsequent annealing [6]. The additions required for good magnetic performance could be quite different to those required for the processing. Similar alloy design principles may have to be used when designing magnetic alloys to be produced by the mechano-synthesis route. The alloy design requirements may be framed in the form of the following questions: i. What elements aid the breakdown of the crystals rapidly to NC levels? ii. What elements control the growth of the nano-crystals during subsequent high temperature processing? iii. What elements enhance the magnetic performance of the material? iv. How do elements added for each purpose interact among themselves, and also interfere with other processing and performance requirements? 0925-8388/$ – see front matter © 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.jallcom.2004.08.029