The effect of rare earth alloying on the hot workability of duplex stainless steel — A study using processing map

Effect of Rare Earth (RE) on hot workability of duplex stainless steel (DSS) has been investigated using processing map, which is based on the dynamic material model theories and the Prasad instability criterion. It is found that RE narrows hot deformation parametric regions for the presence of the particular yield point-like phenomenon in flow curves and reduces the mismatch in hardness between softer ferrite and harder austenite. At large strains, the efficiency of power dissipation of the tested steel (DSS1) with RE is relatively higher than that of the other one (DSS0) without RE. Microstructure analysis shows that RE contributes to the development of dynamic recrystallization (DRX) in austenite. The optimum hot working domains for both test steels are considered to be at 1423–1473K and 0.01s−1 in which sufficient DRX of austenite develops. As predicted in the processing map, RE can narrow the flow instability region at 1223–1273K caused by bands of flow localization, and can eliminate the unstable domain at 1373–1473K and 1–10s−1 which is related to the microcracks. It is believed that micro-alloyed RE could play an important role in hot workability of DSSs. [Display omitted] •The effect of RE on the yield point-like phenomenon in flow curves is found.•RE can reduce the mismatch between ferrite and austenite.•The optimum hot-working domains of DSSs are determined.•The beneficial effect of micro-alloyed RE on hot workability of DSS is discussed.