Effect of powder synthesis method on the microstructure of oxide dispersion strengthened Fe-Cr-Al based alloys

An optimum route to fabricate oxide dispersion strengthened ferritic superalloy with desired microstructure was investigated. Two methods of high energy ball milling or polymeric additive solution route for developing a uniform dispersion of Y₂O₃ particles in Fe-Cr-Al-Ti alloy powders were compared on the basis of the resulting microstructures. Microstructural observation revealed that the crystalline size of Fe decreased with increases in milling time, to values of about 15-20 nm, and that an FeCr alloy phase was formed. SEM and TEM analyses of the alloy powders fabricated by solution route using yttrium nitrate and polyvinyl alcohol showed that the nano-sized Y-oxide particles were well distributed in the Fe based alloy powders. The prepared powders were sintered at 1000 and 1100 °C for 30 min in vacuum. The sintered specimen with heat treatment before spark plasma sintering at 1100 °C showed a more homogeneous microstructure. In the case of sintering at 1100 °C, the alloys exhibited densified microstructure and the formation of large reaction phases due to oxidation of Al.