Dynamic recrystallization of Fe-Cr alloys by atmospheric-controlled induction-heating fine particle peening

Atmospheric-controlled induction-heating fine particle peening (AIH-FPP) was conducted in a N2 atmosphere to form ultrafine grains on the surface of Fe-Cr alloys. The surface microstructure of Fe-2%Cr alloy and Fe-10%Cr alloy treated with AIH-FPP at 973 K and 1073 K was characterized using optical microscopy, scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and transmission electron microscopy (TEM). AIH-FPP can be used as a thermomechanical process to form ultrafine grains on the surface of Fe-Cr alloys because strain is induced by AIH-FPP at a high rate and high temperature during dynamic recrystallization. In particular, the grain size of Fe-Cr alloys tends to decrease with increasing AIH-FPP treatment time. This is attributed to the increase in the strain induced by AIH-FPP with increasing AIH-FPP treatment time during dynamic recrystallization. Thus, the AIH-FPP-induced stratification structure composed of fine grains becomes more pronounced with increasing treatment time. Furthermore, the AIH-FPP treatment temperature at which fine grains are formed depends on the Cr concentration of the Fe-Cr alloys.