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

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 α-(Fe, Cr) and from α-(Fe, Cr) to α (Fe-rich ferrite)+α′ (Cr-rich ferrite) as well as the precipitation of (Fe, Cr)7C3, (Fe, Cr)23C6, and σ. 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 α′ phase and the precipitation temperature of (Fe, Cr)23C6 and narrows the precipitation temperature range of (Fe, Cr)7C3. In addition, the investigations using high temperature in-situ XRD further validate the separation of α (Fe-rich) and α′ (Cr-rich) as well as the absence of ferrite to austenite transformation in FeCrAl alloy during solidification.