EBSD analysis and mechanical properties of alumina-forming austenitic steel during hot deformation and annealing

Abstract

Microstructural evolutions during hot deformation and annealing of alumina-forming austenitic (AFA) steel were investigated using electron backscatter diffraction (EBSD). Tensile properties of deformed and as-received AFA steels were also tested. The yield strength and ultimate tensile stress of deformed AFA steel increase gradually with the increase in rolling reduction, while the fracture elongation decreases rapidly. Specifically, after hot-rolling with the reduction of 40%, the yield strength of the annealed specimen is high to 773.2 MPa, and the fracture elongation of this sample is about 43.6%. The excellent mechanical properties can be attributed to the smaller average grain, larger Schmid factor and coincident site lattice (CSL) boundaries. Such a rapid decline of the elongation of AFA steel occurs due to increasing low angle grain boundaries (LAGB, <15°), the crystal defects and the degree of work hardening with the increase in rolling deformation. An approachable strategy to improve the tensile properties of annealed samples is to effectively hinder the dislocation motion during annealing at 700 °C when few LAGBs could transform into high angle grain boundaries (HAGB, >15°).