Tohru Yamasaki1, Yoshikiyo Ogino1, Terukazu Honda2 and Yoshiyuki Amemiya3
1Department of Materials Science, Faculty of Engineering, Himeji Institute of Technology, Himeji
In order to obtain information about the annealing treatment dependence of the ductile-brittle transition temperature (DBTT) of Fe-B-Si amorphous alloys, single bend properties at various temperatures, Mössbauer effects and small angle X-ray scattering (SAXS) using synchrotron radiation were examined. The rising behavior of DBTT depends on the annealing temperature. In the case of Fe77B13Si10 alloy, DBTT saturates to about 290 K when annealed below 623 K. On the other hand, when annealed above 633 K, DBTT rises up to about 290 K at the initial periods of annealing and then steadily rises with increasing annealling times. These results indicate that the embrittling reaction proceeds in two stages: below about 623 K, only the first-stage embrittlement occurs and at higher temperatures the second-stage occurs following the first-stage reaction. The Curie temperature measured by DSC and the SAXS intensity begins to increase from 620 K which well coincides with the starting temperature of the second-stage embrittlement. Mössbauer effect measurement suggests that the first-stage embrittlement is caused by the redistribution of the structural defects which has weak temperature dependence, and the second-stage is caused by the developement of Fe3(B, Si) type and Fe-rich type compositional short-range orders.
iron boron silicon alloys, amorphous metal temper embrittlement, ductile brittlle transition temperature, Mössbauer spectroscopy, small angle X-ray scattering, synchrotron radiation
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