Bulk Amorphous Formation and Magnetic Properties of Nd-Fe-Co-Al Alloys by the New Gas Jet Flow Type Levitating Process

Abstract

The amorphous formation ability and the magnetic properties of Nd₆₀Fe_30−xCo_xAl₁₀ (x=10, 15, 20 or 30) alloys in the containerless process were studied by the new gas jet flow type levitating process. The gas jet flow type levitating process enables solidification without any container wall by the inert gas jet. The samples were solidified at the cooling rate of around 100 K/s. Then, the undercooling of samples exhibits high values (ΔT=60–150 K). From X-ray diffraction measurements, the Nd₆₀Fe_30−xCo_xAl₁₀ samples exhibit a typical broad diffraction pattern for an amorphous structure. The DTA curves of x=10, 15 and 20 showed an exothermic peak due to the crystallization. That is, it was revealed that the Nd₆₀Fe_30−xCo_xAl₁₀ samples formed bulk amorphous. Also, the coercivity is 1.6, 3.3 and 3.6 kOe for the Nd₆₀Fe₂₀Co₁₀Al₁₀, Nd₆₀Fe₁₅Co₁₅Al₁₀ and Nd₆₀Fe₁₀Co₂₀Al₁₀, respectively. From the thermomagnetic curves, the Curie temperature is determined to be 463, 482 and 482 K for the Nd₆₀Fe₂₀Co₁₀Al₁₀, Nd₆₀Fe₁₅Co₁₅Al₁₀ and Nd₆₀Fe₁₀Co₂₀Al₁₀, respectively. In the M-H loops and the thermomagnetic curves, this difference between x=10 and x=15, 20 may depend on the microstructure.