Isothermal nanocrystallisation behaviour of melt spun Al86Ni9Mm5 (Mm misch metal) amorphous alloy

The structure and mechanical properties of melt spun Al(86)Ni(9)Mm(5) alloy ribbons in both as solidified amorphous and heat treated nanocomposite conditions were investigated using DSC, XRD, TEM, and Vickers microhardness techniques. Primary crystallisation of the amorphous alloy resulted in the formation of fine nanocrystalline fcc-Al particles embedded in an amorphous matrix forming a nanocomposite. The growth behaviour of the primary fcc-Al particles under isothermal conditions was investigated. The hardness of the composite varied with the solute content in the amorphous phase and the microstructure after heat treatment. The hardening in these nanocomposites; was quantitatively explained using a rule of mixtures model based on the volume fraction of the amorphous matrix and the Al particles. The nanometre sized particles were treated as perfect materials and the matrix was treated as an amorphous material, in which the solute concentration increased as the volume fraction of the Al particles increased. The calculated results for the heat treated specimens using the rule of mixtures based on the isostress model have been found to be in good agreement with the experimentally obtained results. MST/5646 Dr Hong, Dr Kim, and Dr Chun are with the Rapidly Solidified Materials Research Center (RASOM), Chungnam National University, Taedok Science Town, Taejon 305-764, South Korea. Dr Suryanara.Vana (csuryana@mail.ucf.edu) is in the Department of Mechanical, Materials and Aerospace Engineering, University of Central Florida, Orlando, FL. 32816-2450, USA. Manuscript received 12 September 2002; accepted 19 September 2002. (C) 2003 IoM Communications Ltd. Published by Maney for the Institute of Materials, Minerals and Mining.