Effect of strengthening mechanisms on mechanical properties of alumina-forming austenitic steel after pre-strain

Alumina-forming austenitic (AFA) steel, a promising candidate for use in high-temperature components of ultrasupercritical power plants, has high creep strengths and outstanding high-temperature corrosion resistance. The effects of microstructural evolution on the mechanical properties of Fe-20Ni-14Cr-3Al alumina-forming austenitic (3Al-AFA) steel with micro-cold deformation were investigated by multiple characterization methods, and the micro-cold deformation process was analyzed by conducting compression experiments. Tensile properties and hardness were also examined. The results show that the reduction of deformation has significant influences on the increase in the density of dislocation, the reduction of grain size, and the distribution of precipitates, which play an essential role in the enhancement of mechanical properties. As the reduction of deformation increases, the density of dislocations rises, the fragmentation of grains results in a reduction of grain size, and the distribution of precipitates at the grain boundaries gradually increases, which causes a rise in strength and a decrease in elongation. Since the elastic deformation range expands with an increase in deformation before the strain reaches 5 % of the CR0 sample in the compression test, the variation in the average grain aspect ratio between a reduction of 2 % and 6 % is relatively small. It contributes more to hardness and strength when the grain aspect ratio is high.