Fast development of high coercivity in melt-spun Sm(Co,Fe,Cu,Zr)z magnets

Abstract

A simple method was developed for magnetic hardening melt-spun Sm(Co,Fe,Cu,Zr)z alloys. The as-spun ribbons reached a coercivity of 2.8 T only by slow cooling from 850 to 400 °C, without the standard solid solution and isothermal aging treatments which are required for a bulk precipitation hardened 2:17 SmCo alloy. A single 1:7 phase, identical to that found in as-solubilized ribbons, was obtained in the as-spun state. At the same time, Cu and Zr are supersaturately dissolved in the 1:7 matrix by melt spinning due to its very high cooling rate. Thus, solid solution treatment can be avoided for melt-spun materials. After aging, more lamellar phase with larger width was observed by transmission electron microscope in ribbons without treatment in solution. This leads to faster development of a uniform finer cellular microstructure with a Cu-rich 1:5 cell boundary phase, which gives rise to stronger domain-wall pinning and therefore to higher coercivity.