The Influence of Heat Treatment Regime on the Microstructure and Magnetic Properties of Melt-spun Nd—Fe—B with Nd Low Content

In recent time the study topic of many scientific institutions throughout the world is the process of obtaining high-coercive magnetic materials based on Nd-Fe-B, by the method of rapid quenching from the alloy melt of desired chemical composition, so-called “melt spinning” method. Cooling speed range in which optimal results are achieved is rather narrow so that heat treatment of R/Q Nd-Fe-B alloys is needed in order to achieve the maximal coercivity. Crystallization and thermomagnetic behaviour of melt-spun Nd-Fe-B alloy with Nd low content was observed through phase transformation, for defined cooling rate and different heat treatment regime. The crystallization kinetics and activation energy of investigated alloy were observed by DTA measurements. The phase composition of the samples was investigated by conventional XRD analysis and Mossbauer spectroscopic phase analysis (MS). For determining the critical temperature of phase and thermomagnetic transformations, magnetic measurements were additionally carried out. Comparison of the experimental results obtained by different investigation techniques enabled more complete comprehension of the crystallization process during the heat treatment. Analysis of experimental results also enabled better insight in relationship between microstructure and magnetic properties in function of heat treatment regime.