ISSN:
1662-9779
Source:
Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
Topics:
Physics
Notes:
Research performed at Ghent University, regarding new production methods forelectrical steel, has shown that high silicon steel suffers an ageing phenomenon at roomtemperature. Recent studies carried out by the same group using different analysis techniques(Mossbauer spectroscopy, neutron diffraction, etc) brought to light a probable process of orderingtowards the D03-structure, which is responsible for the observed low ductility during cold rollingand makes the processing of steel extremely difficult. In addition, the Si-steels become more brittleas the delay time between hot and cold rolling is increased.Frequency dependent internal friction (FDIF) studies were performed on different Fe - Si alloyswith a Si content varying from 3.73 at. % to 8.7 at. % immediately after several thermal treatmentsand compared with ultra-low carbon steel. The evolution of relaxation peaks during the IFmeasurements, performed at constant room temperature, helps to understand the ageingmechanisms. Three processes have been observed: firstly, as expected, addition of Si reduces thecarbon Snoek peak. Secondly, a peak associated to C - Si is formed. Thirdly, a low frequency peakassociated with Zener relaxation (Si atom pairs) appears for a content of approximately 3.77 wt. %Si. The two latter peaks decrease with ageing time and in the case of the Zener peak there is anotable displacement to higher frequencies with a small increase of the Si content. The reduction ofthe peaks during the ageing after annealing is more noticeable in quenched specimens than in aircooled ones, and in furnace cooled specimens the reduction is even smaller, indicating that theprocess is really an ageing phenomenon.Room temperature short-range ordering might explain both the lowering of the Zener peak andthe observed macroscopic embrittlement
Type of Medium:
Electronic Resource
URL:
http://www.tib-hannover.de/fulltexts/2011/0528/02/24/transtech_doi~10.4028%252Fwww.scientific.net%252FSSP.137.83.pdf
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