Effects of quenching speeds on microstructure and magnetic properties of novel SmCo6.9Hf0.1(CNTs)0.05 melt-spun ribbons

By adding carbon nanotubes (CNTs) to SmCo6.9Hf0.1, novel SmCo6.9Hf0.1(CNTs)(0.05) as-cast alloy has been prepared, which consists of Sm(CO,Hf)(7) as the main phase, a small amount of SmCo5 and a particle-like grain boundary phase Hf(CNTs). SmCo6.9Hf0.1 (CNTs)(0.05) ribbons melt-spun at speeds of 10-50 m s(-1) have a single TbCu7-type structure. Increasing the quenching speed can result in a decrease in ribbon thickness and grain boundary width. Meanwhile, the grain size tends to be smaller and the grain boundary phase tends to be more dispersed. A new Sm(Co,Hf)(7)(CNTs)(x) boundary phase may be formed in SmCo6.9Hf0.1(CNTs)(0.05) ribbons. Increasing the quenching speed can also enhance coercivity, remanence and remanence ratio. The ribbons melt-spun at a speed of 50 m s(-1) display the best magnetic properties: H-ci = 18.781 kOe, M-s2T = 76.87 emu g(-1), M-r = 66.79 emu g(-1) and M-r/M-s2T = 0.87. (C) 2009 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.