Solidification microstructure and phase transition of La-Nd-Fe alloys

Abstract The solidification microstructure and phase transition of ten La-Nd-Fe alloys were studied experimentally by scanning electron microscopy (SEM) with energy dispersive x-ray spectroscopy (EDS) and differential thermal analysis (DTA). Phase compositions and phase transition temperatures of La-Nd-Fe alloys were measured and the formed phases were identified. The solidification behavior of La-Nd-Fe alloys was analyzed based on the experimental results of both solidification microstructure and phase transitions with the reported Nd-Fe, La-Fe and La-Nd sub-binary phase diagrams. The results indicated that the solidification processes of all La-Nd-Fe alloys begin with the precipitation of primary phase fcc( γ -Fe) and then follow by the formation of bcc( α -Fe) and/or Fe 17 Nd 2 phases through different peritectic reactions. The solidification microstructure of three Fe 65 La 29 Nd 6 , Fe 65 La 25 Nd 10 and Fe 65 La 22 Nd 13 alloys presents three-phase microstructure with bcc( α -Fe), Fe 17 Nd 2 and fcc(La,Nd) phases, while that of three Fe 65 La 19 Nd 16 , Fe 65 La 9 Nd 26 and Fe 65 La 15.5 Nd 19.5 alloys shows three-phase microstructure with bcc( α -Fe), Fe 17 Nd 2 and dhcp(La,Nd) phases. The two-phase micorstructure with Fe 17 Nd 2 and dhcp(La,Nd) ohases was formed in the solidification microstructure of four Fe 65 La 12 Nd 23 , Fe 65 La 6.5 Nd 28.5 , Fe 65 La 4 Nd 31 and Fe 65 La 1.5 Nd 33.5 alloys. Moreover, no stable ternary intermetallic compound was found in the present experiments. The solidification microstructure and phase transition of La-Nd-Fe alloys would provide a basis for the design of La-Nd-Fe-B magnetic alloys.