QUANTITATIVE PHASE-ANALYSIS OF METASTABLE STRUCTURE IN A LASER MELTEDFE-C ALLOY .2. STRUCTURAL-ANALYSIS OF OVERLAPPING TRACKS BY X-RAY-DIFFRACTION

Citation
M. Cernansky et al., QUANTITATIVE PHASE-ANALYSIS OF METASTABLE STRUCTURE IN A LASER MELTEDFE-C ALLOY .2. STRUCTURAL-ANALYSIS OF OVERLAPPING TRACKS BY X-RAY-DIFFRACTION, Journal of Materials Science, 31(4), 1996, pp. 995-1004
Citations number
42
Categorie Soggetti
Material Science
ISSN journal
00222461
Volume
31
Issue
4
Year of publication
1996
Pages
995 - 1004
Database
ISI
SICI code
0022-2461(1996)31:4<995:QPOMSI>2.0.ZU;2-F
Abstract
Quantitative X-ray diffraction phase analysis was utilized to investig ate the structure of a Fe-3.5 wt% C alloy after laser melting. The mea surements were taken on surfaces modified by a series of equidistant l aser tracks with overlappings k = 0.25, 0.50 and 0.75, and the results were extrapolated to the non-interfering tracks. On the same samples, the microstructure was observed by scanning electron microscopy. The structure of the rapidly solidified surface layers consists of alpha-F e (ferrite and martensite), gamma-Fe (retained austenite) and cementit e. The results of X-ray diffraction point to a very high amount of car bide indicating a non-stoichiometric composition of cementite. Besides , the volume fraction of alpha-Fe increases with increasing coefficien t of overlapping k. At the same time, the volume fraction of cementite decreases while the content of gamma-Fe remains nearly constant. The changes are attributed to decomposition of the metastable carbide due to tempering of the former tracks by the following laser passes. This thermal effect was quantified on the base of the heat-transfer model o f moving Gaussian beam.