Papers by Author: Sophie Rivoirard

Abstract: In this study, a hot forging process is applied to Nd-Fe-V as cast alloys in order to develop both the microstructure and the crystallographic texture appropriate for permanent magnet properties. A neutron diffraction texture analysis is used to account for the extrinsic magnetic anisotropy: the stabilisation of the Nd(Fe,V)12 hard magnetic phase has been achieved during forging but its extrinsic anisotropy level remains low. Attempts to understand this phenomenon are made through a discussion on the Nd-Fe-V alloy rheological and mechanical behaviour and a comparison with Nd-Fe-B permanent magnets.

Abstract: A high speed hot forging process was applied to Nd-Fe-B and Nd-Fe-V as cast alloys in order to develop both the microstructure and the crystallographic texture appropriate for permanent anisotropic magnet properties. Neutron diffraction texture analyses are used to demonstrate the effect of the hot forging process on both kind of alloys. Microstructural changes are an important feature on forging in both cases. Coercivity is developed in the Nd-Fe-B alloy mainly from grain size reduction and disappearance of free iron. Stabilisation of the Nd(Fe,V)12 hard magnetic phase is achieved from the iron and Nd-rich microstructure of the starting Nd-Fe-V material. A comparison of the crystallographic textures of Nd2Fe14B and Nd(Fe,V)12 phases is done to account for the development of extrinsic magnetic anisotropy. In both cases, a nearly fibre texture is obtained in correlation with the symmetry of the deformation. However, the orientations are quite different in both alloys and the consequences on the magnetic properties are evidenced.