Phase transformations of mechanically alloyed Fe-Cr-P-C powders

• Published in: Journal of alloys and compounds Vol. 393; no. 1-2; pp. 194 - 203
• Main Authors: Bensebaa, N, Alleg, S, Greneche, J M
• Format: Journal Article
• Language: English
• Published: 03.05.2005
• ISSN: 0925-8388
• DOI: 10.1016/jjallcom.2004.10.016

Fe77Cr4P8C11 alloy was prepared by mechanical alloying (MA) of elemental Fe, Cr, P and C (graphite) powders in a planetary ball mill type Fritsch P7 under argon atmosphere. Morphological changes, microstructural and structural evolutions during ball milling were followed by scanning electron microscopy (SEM), X-ray diffraction (XRD) and 57 Fe Mossbauer spectrometry (MS) as a function of the milling time. The crystallite size refinement against the milling time is accompanied by an increase of the atomic level strain. After 6 h of milling, the dissolution of phosphorous into the a-Fe matrix is evidenced by the formation of a small amount (~4%) of the paramagnetic Fe2P phase as revealed by Mossbauer spectrometry. The complete mixing of all the elemental powders at the atomic level is achieved at 12 h of milling and results, after 24 h, in an amorphous matrix where nanocrystalline phosphides and carbides with nearly equal crystallite sizes are embedded. Further milling time up to 190h gives rise to the formation of both the orthorhombic and the hexagonal (FeCr)7C3 carbide as well as the superparamagnetic epsilon'-Fe2.2C carbide through the recrystallisation of the amorphous phase.