Structure-property correlation of AISI 1080 steel subjected to cyclic quenching treatment

Annealed AISI 1080 steel bars were subjected to cyclic heat treatment for different number of cycles, viz. 1-cycle, 2-cycle and 3-cycle. Each cycle consisted of inserting the specimen in an electric resistance furnace at a temperature of 775 °C (in fully austenitic region) and holding for a short duration (6 min), followed by oil quenching to the room temperature. Besides, tempering treatment (at 300 °C for 1 h) was also provided after 3 cycles of heat treatment. Such a typical thermal cycling resulted in the evolution of a novel microstructure that comprised of microscopic clusters and submicroscopic spheroids of cementite in a matrix of martensite after 3 cycles of heat treatment. Accordingly, much higher hardness (845 HV), strength (UTS=1609 MPa) and equivalent ductility (% Elongation=8) were achieved with 3 cycles of heat treatment as compared to conventional hardened and tempered AISI 1080 steel (Hardness=616 HV, UTS= 1206 MPa, % Elongation=9). Execution of tempering after 3 cycles of heat treatment resulted in reasonable strength (UTS=1256 MPa) with higher ductility (% Elongation=13).