Effects of interstitial solute atoms on the very low strain-rate deformations for an IF steel and an ultra-low carbon steel

In order to investigate the effects of interstitial solute atoms on very low strain-rate deformation of steel by using an interstitial free (IF) steel and an ultra-low carbon (ULC) steel, creep tests and crosshead-arresting tests were conducted at room temperature. The concentrations of solute carbon and solute nitrogen for the ULC steel were 8 and 12 ppm, respectively, and were about 20 times higher than those of the IF steel. The static tensile tests showed that the tensile properties in the two steels were quite similar. However, the room temperature creep test and the crosshead-arresting test showed that their deformation behaviors were significantly different. The very low strain-rate deformation of the ULC steel was associated with the so-called dynamic strain aging, which appeared at a critical strain rate of 5.8 × 10−8 s−1.