Experimental studies on nitrogen solubility in Nd₂Fe₁₄B alloy in the temperature range 773-1143 K

When nitrogen is dissolved in several rare earth-iron alloys, their magnetic properties are known to be significantly improved. The present work was undertaken to investigate the solution of nitrogen in Nd₂Fe₁₄B in the temperature range 773-1143 K. The total nitrogen intake was measured continuously by thermogravimetry and the amount of dissolved nitrogen was determined by the vacuum fusion technique. The reaction at all temperatures resulted in the formation of an outer nitride layer and an unreacted inner core where no internal nitride formation could be observed by optical microscopy. Depending on temperature and exposure time, significant amounts of nitrogen could be dissolved in the alloy. The X-ray diffraction data revealed major differences in the structure of the outer complex nitride layer at various temperatures.