PHASE-RELATIONS AND THE MARTENSITIC-TRANSFORMATION IN FE-N-BASED THIN-FILMS

The aim of the present study is to elucidate the phase relationships w ith respect to the formation of the phase Fe16N2 in Fe-N-based reactiv e-sputtered thin films. This compound is not formed during the sputter ing process but rather through a martensitic transformation if the thi n films undergo a heat treatment and a subsequent heat or cooling trea tment. To realize thin films with a high volume fraction of Fe16N2, a knowledge of the phase relationships of the system in question is an e ssential prerequisite to optimize the heat and cooling treatment. Ih c onnection with this, the phase relationships in austenitized and subse quently transformed Fe-N based thin films with different compositions have been studied by means of magnetic measurements and X-ray diffract ion. The transition temperatures of the martensitic transition (in the course of which Fe16N2 is formed) also have been determined by means of magnetic measurements. Furthermore, the effects of Ni additions on the phase relationships and the martensitic transformation temperature s have been studied. Finally, the correlation between the Fe16N2 forma tion and the composition of the thin films is discussed.