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MM: Metall- und Materialphysik

MM 28: Amorphous and Liquid Materials III

MM 28.4: Vortrag

Donnerstag, 30. März 2006, 12:30–12:45, IFW B

Cooling rate controlled microstructure and magnetic properties of metastable Fe₂₀Nd₈₀ alloys — •Jürgen Eckert¹, Golden Kumar^2,3, Jürgen Eckert¹, Annett Gebert², Ludwig Schultz², and Albrecht Wiedenmann⁴ — ¹Darmstadt University of Technology, Petersenstr. 23, D-64287 Darmstadt, Germany — ²IFW Dresden,PF 270016, D-01171 Dresden, Germany — ³Present address: NIMS, 1-2-1 Sengen, Tsukuba 305-0047, Japan — ⁴Hahn-Meitner Institut Berlin, Glienickerstr. 100, D-14109 Berlin, Germany

The microstructures and magnetic properties of as-cast and annealed Fe₂₀Nd₈₀(hypereutectic) alloys were studied. Depending on the cooling rate the Fe₂₀Nd₈₀ alloys solidify into various metastable eutectic-like structures, which present a wide range of coercivity values varying from 0.2 to 0.48 T measured at room temperature. The alloys cooled at rates faster than 50 K/s display fine eutectic-like regions of Nd + A₁ and are hard magnetic. Transmission electron microscopy (TEM) studies clearly show that the hard magnetic A₁ regions are microscopically inhomogeneous. The alloys cooled slower than 25 K/s show a discontinuous rod-type eutectic of Nd + Fe₁₇Nd₂ and, consequently, exhibit a soft magnetic behaviour. The correlations between the cooling rate, the microstructure, and the coercivity of the Fe₂₀Nd₈₀ alloys are discussed. This work was supported by the German Science Foundation (DFG) via the DFG priority program No-dqPhasenumwandlungen in mehrkomponentigen SchmelzenNo-dq under grant Ec 111/11.