TY - JOUR
T1 - Composition-dependent variation of magnetic properties and interstitial ordering in homogeneous expanded austenite
AU - Brink, Bastian K.
AU - Ståhl, Kenny
AU - Christiansen, Thomas Lundin
AU - Frandsen, Cathrine
AU - Hansen, Mikkel Fougt
AU - Somers, Marcel A. J.
PY - 2016
Y1 - 2016
N2 - The crystal structure and magnetic properties of austenitic stainless steel with a colossal interstitial content, so-called expanded austenite, are currently not completely understood. In the present work, the magnetic properties of homogeneous samples of expanded austenite, as prepared by lowerature nitriding of thin foils, were investigated with magnetometry and Mössbauer spectroscopy. At room temperature, expanded austenite is paramagnetic for relatively low and for relatively high nitrogen contents (yN = 0.13 and 0.55, respectively, where yN is the interstitial nitrogen occupancy), while ferromagnetism is observed for intermediate nitrogen loads. Spontaneous volume magnetostriction was observed in the ferromagnetic state and the Curie temperature was found to depend strongly on the nitrogen content. For the first time, X-ray diffraction evidence for the occurrence of long-range interstitial order of nitrogen atoms in expanded austenite was observed for high nitrogen contents.
AB - The crystal structure and magnetic properties of austenitic stainless steel with a colossal interstitial content, so-called expanded austenite, are currently not completely understood. In the present work, the magnetic properties of homogeneous samples of expanded austenite, as prepared by lowerature nitriding of thin foils, were investigated with magnetometry and Mössbauer spectroscopy. At room temperature, expanded austenite is paramagnetic for relatively low and for relatively high nitrogen contents (yN = 0.13 and 0.55, respectively, where yN is the interstitial nitrogen occupancy), while ferromagnetism is observed for intermediate nitrogen loads. Spontaneous volume magnetostriction was observed in the ferromagnetic state and the Curie temperature was found to depend strongly on the nitrogen content. For the first time, X-ray diffraction evidence for the occurrence of long-range interstitial order of nitrogen atoms in expanded austenite was observed for high nitrogen contents.
KW - Low temperature surface hardening
KW - Gas nitriding
KW - Expanded austenite
KW - Magnetostriction
KW - Mössbauer spectroscopy
U2 - 10.1016/j.actamat.2015.12.043
DO - 10.1016/j.actamat.2015.12.043
M3 - Journal article
VL - 106
SP - 32
EP - 39
JO - Acta Materialia
JF - Acta Materialia
SN - 1359-6454
ER -