Thermal stability of ultrafine grained Fe–Cr–Ni alloy

Equal channel angular pressing was used to refine the microstructure of a Fe–14Cr–16Ni (wt.%) alloy. The as-processed alloy had predominantly equiaxed austenite fine grains with an average grain size of 0.4 μm and a low fraction of deformation induced martensite. Ex situ isothermal annealing experiments showed the fine microstructure was thermally stable up to 673 K, and abnormal grain growth occurred at ∼873 K. In situ annealing studies in a transmission electron microscope revealed the coarsening of grains. Analysis of grain growth kinetics from 873 to 1073 K yielded average activation energy of grain growth to be ∼207 kJ/mol. The grain growth mechanisms and annealing induced evolution of mechanical properties were discussed.

► Ultrafine grained Fe–Cr–Ni alloy was processed by equal channel angular pressing. ► The ultrafine microstructure and microhardness were thermally stable up to 673 K. ► Abnormal grain growth occurred at ∼873 K. ► Activation energy of grain growth from 873 K to 1073 K was ∼207 kJ/mol.