STRUCTURE AND MAGNETIC-PROPERTIES OF BALL-MILLED IRON NITRIDE POWDERS

In the present work we studied the influence of ball milling of iron n itrides-alpha' martensite+gamma austenite in the NH3 atmosphere on the content of nitrogen, the phase composition, and the magnetic moment o f nitrides. Only a small increase in the nitrogen content (from 6.5 to 7.0 at.% N) was found after milling. XRD and Mossbauer spectroscopy a nalyses of milled samples showed that at first austenite was transform ed into nanocrystalline alpha-Fe and amorphous gamma'-Fe4N and FeNx du ring milling. The decrease in the austenite content was gradually acco mpanied also by the change of martensite into the above mentioned comp ounds. The structure of the samples milled for the longest time (8 h) was so destroyed that these samples were not able to be transformed in to alpha ''-Fe16N2 by subsequent annealing. The magnetic moment of mil led samples firstly slightly increased and then decreased with increas ing milling time. (C) 1998 Elsevier Science S.A.