Influência do disprósio nas propriedades magnéticas dos ímãs permanentes à base de NdFeB obtidos por HD

Abstract

FARIA, Marcela E. M. Dysprosium influence on magnetic properties of NdFeB-based permanent magnets obtained by HD. 2022. 84 p. Dissertation (Master in Nuclear Technology) -Institute of Energetic and Nuclear Research, -IPEN/CNEN/SP. São Paulo.The rare-earth magnets were showed important in the development of electromagnetic devices. However, these magnets had promoted advances, the low Curie temperature prevent its usage in high temperatures. It's known that the dysprosium addition improves the magnetic properties, control the grain size, and raise the working temperature. The current research focus on minimizing the quantity of dysprosium used in the magnets. A rich dysprosium alloy was produced in the Technological Institute Research (IPT) to be used as additive in the magnetic alloys (Nd14,1B6,1Febal and Nd8,7Dy4,9B6,1Febal), acquired with Less Common Metal Ltd. Although these alloys after an X-ray analyzes, was determined the presence of free iron, that's deleterious for the magnetic properties. It was necessary to realize a heat treatment to eliminate the Fe-α. This present dissertation analyzes the influence of dysprosium variation within the magnets (0%, 10%, 20% e 30%) and evaluate the variation of processing parameters, like the time of the heat treatment (without heat treatment, 2.5h and 5h) and the milling time (45 min, 53 min and 60 min). The variation had the object to investigate which variation would provide better grain sizes for the sinterization and the magnetic properties. Better results were obtained for heat treatment of 5h, milled for 60 min and 10%w of Dy; obtained iHc = 736 k.A.m -1 , Jr = 1.18 T and BHmax = 4.32 k.J.m -3 .