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Effect of the process control agent in the ball-milled powders and SPS-consolidation temperature on the grain refinement, density and Vickers hardness of Fe14Cr ODS ferritic alloys

Mihalache, V., Mercioniu, I., Velea, A., Palade, P.
Powder technology 2019 v.347 pp. 103-113
ethanol, glass transition, hardness, heat, microstructure, powders, process control, steel, temperature
Fe-14Cr-0.4Ti-0.25Y2O3 ferritic steels were produced by varying the amount of residual process control agent, PCA (ethanol), in the ball-milled powders and changing the spark-plasma-sintering, SPS, temperature. Near theoretical density (99.3%), high Vickers hardness (501–920 HV, measured by applying a load of 100 g for 5 s) and fine grain size (26–36 nm), very stable against heating, can be achieved on ODS ferritic steels, consolidated from powders with a low amount of PCA and processing temperature in the range of 1000 °C–1100 °C. Additional grain refinement occurs near α → γ transition which is generated by the reaction of the traces of PCA with the ferritic matrix upon heating. High local temperatures and the evolved thermally activated processes, at the contact points between particles/at the particle surfaces during SPS-consolidation, were demonstrated to be the main factors responsible for improved densities and hardness. The role of PCA in the sintering, thermal and microstructure particularities and its impact on the quality of the final steel was thoroughly analysed throughout the work.