Abstract
The effect of heat treatment on the chemistry and structure of an Fe-based bulk metallic glass (BMG) Fe48Cr15Mo14C15B6Y2 (SAM 1651) was examined experimentally. Chemical segregation was found in the as-received material, with islands 10 to 200 nm in diameter enriched in Y, Mo, and C and depleted in Fe and Cr, with respect to the surrounding matrix. Heat treatment in the range of 600 °C to 800 °C caused partial devitrification of the BMG with the formation of nanocrystalline (Fe, Cr)23C6 and (Fe, Cr)7C3 carbides in a matrix of the remaining amorphous phase. The devitrification process followed a primary crystallization route. Amorphous particle-free zones (PFZs) in the devitrified material were found, corresponding to the Y-Mo–rich islands in the fully amorphous SAM 1651. The formation of Cr-rich carbide during devitrification caused the formation of nanometer-sized Cr-depleted zones surrounding the carbide particles, which is detrimental to the corrosion performance of the alloy after thermal exposure.
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