Phase - Structurial analysis of Rapid Quenched Powders of Nd_(2)Fe_(81)B_(17) alloys after different thermal treatement mode

摘要

The influence of the devitrification temperature in the range 560 - 780 deg C with duration 20 minutes on the phase composition and hysteresis properties of the rapid quenched powders of Nd_(2)Fe_(81)B_(17) alloy systematically were studied. Experiment established, than anneal temperature has a strong influence on coercitivity and remanence then might be attained the value ordinal 190 kA/m and 0.31 T. After ageing at the temperatures lower than 550 deg C the powders are magnetically soft, H_(ci) approx 0 kA/m. After heart treatment in the range 600 - 660 deg C the powders are hard magnetic and have maximum properties. After ageing at the temperatures higher than 700 deg C hysteresis properties are slumped. Strong influence of ageing temperature on phase composition of rapid quenched powders of Nd_(2)Fe_(81)B_(17) alloys has been investigated. In annealed mode and after ageing at the low temperate the main phase in these powders is amorphous phase. After heart treatment in the range 600 - 660 deg C the powders has three principal phase, namely, the main constituents of their volume (approx70percent) are the magnetically soft a-Fe and Fe_(3)B phases and the fraction on the main hard magnetic phase Nd_(2)Fe_(14)B (approx30percent). Jump of content a-Fe with synchronous degradation volume fraction of Fe_(3)B and Nd_(2)Fe_(14)B after ageing at the temperatures higher than 700 deg C have been observed. Moreover at the temperatures higher than 700 deg C notably increase of the blocks size have been observed. Correlations between hysteresis properties and phase composition have been researched. Henkel plots have been drawn and analyzed, which indicate of the presence of domination of the exchange coupled interactions between hard and soft grains in the ribbons. Obtained results are discussed from position of formation in this powders exchange - spring structure, for the purpose of preparation maximum magnetic properties and perspective to subsequent manufacturing application.