Production and characterization of Al additive Nd-Fe-B alloy

In this study; Nd-Fe-B-based alloys with pure Nd14Fe81B5 and Al doped Nd14-xFe81AlxB5 (x = 1, 2, 3, 4, 5) compositions produced by vacuum arc melting process were investigated the effect of the material on magnetic properties, microstructure and corrosion resistance under different heat treatment temperatures. It is aimed to investigate both the effect of the amount of additives and the effect of temperature on the Nd-Fe-B based alloys in a systematic way. The phases commonly involved in the XRD phase analysis of the samples are Nd2Fe14B and iron phases. The Nd11Fe81Al3B5 specimens annealed at 900 ºC and in the undoped samples have the Nd2Fe17 phase in addition to these two phases. Unlike the other samples, phase transformation occurred in the Nd9Fe81Al5B5 sample which was heat treated at 900 ºC. In this sample, the Nd2Fe15Al2 phase is formed instead of the Nd2Fe14B phase. Magnetization measurements of samples were made with a vibrating sample magnetometer (VSM). The magnetic properties of the samples vary according to the composition of the compounds and the heat treatments made. With the heat treatment applied to the specimens, the magnetic properties (coercive field (Hc), permanent magnetization (Br) and highest magnetization (B)) as well as the coercive field (Hc) values increase. In addition, at different heat treatment temperature values applied, the effect of magnetic properties of Al additive varies. In the samples without heat treatment, the highest B values of the Al additive samples tend to increase proportionally. In the samples heat treated at 700 ºC, highest B and Br increased as the Al content increased, whereas the highest B values decreased with the addition amount in the samples heat treated at 900 ºC. The highest B value of the Nd9Fe81Al5B5 sample, which was heat treated at 900 ºC only, does not tend to decrease. The curie temperatures of the samples decrease as the amount of Al added increases. Microstructure images of the samples were analyzed by scanning electron microscope (SEM) and EDS analyzes were obtained in the back scattered electron (BSE) mode of the SEM device. In the microstructure images of the samples, instead of the long Fe particles appearing darker by heat treatment, it was observed that instead of being circular, somewhat shorter particles were formed. It has been observed that with the Al addition, the elongated Fe particles are formed in the longitudinal direction, and as a result of the increase of the additive amount, the dimension of the longitudinal particles increases. Examination of the corrosion resistance of the samples was carried out by measuring the mass loss of samples up to 25 days at 120 ºC in an air atmosphere. The mass loss occurred only in the Nd14Fe81B5 alloy, which was heat treated at 900 ºC for 10 and 15 days. The reason for the loss of mass in this material is the breakage of the material due to its crispness.