Phase transformation and precipitation during solidification of FeCrAl alloy for automobile exhaust gas purifying systems

摘要

In order to further investigate the solidification process of FeCrAl alloy for automobile exhaust gas purifying systems, the phase transformation and precipitation in FeCrAl alloy with different Al contents were studied using differential scanning calorimetry (DSC), Thermo-Calc calculation and high temperature in-situ X-ray diffraction (XRD). The Thermo-Calc calculation results manifests that the complete solidification process of FeCrAl alloy includes the transformations from L to alpha-(Fe, Cr) and from alpha-(Fe, Cr) to alpha (Fe-rich ferrite)+alpha' (Cr-rich ferrite) as well as the precipitation of (Fe, Cr)(7)C-3, (Fe, Cr)(23)C-6, and sigma. The calculation results with 6.49 wt% Al content are reasonable agreement with the DSC results. The solidification process investigation of FeCrAl alloy with different Al content indicates that the decrease of Al content in FeCrAl alloy increases the forming temperature of alpha' phase and the precipitation temperature of (Fe, Cr)(2)3C(6) and narrows the precipitation temperature range of (Fe, Cr)(7)C-3. In addition, the investigations using high temperature in-situ XRD further validate the separation of alpha (Fe-rich) and alpha' (Crrich) as well as the absence of ferrite to austenite transformation in FeCrAl alloy during solidification. (C) 2017 Elsevier B.V. All rights reserved.