Toughening mechanism of D6A steel during rolling process

Abstract

The rolling-heat treatment process can significantly improve the strength of D6A steel. In order to explore the toughening mechanisms of D6A alloy steel, the micrometer grade D6A alloy steel is obtained by hot rolling and intercritical warm rolling plus annealing process, which consists of ferrite matrix and granular cementite. The microstructure and mechanical properties of the experimental steel were characterized by tensile test at room temperature, SEM, X-ray diffraction and EBSD. The results show that the grain size is refined from 4.5 μm to 1.5 μm with the increase of rolling pass, the cementite content increases gradually, and the proportion of grain boundary with small angle increases. The yield strength and tensile strength increase continuously, while the elongation decreases slightly, indicating that the size of subgrain decreases continuously during the rolling process, grain boundary area, and the resistance to dislocation slip increase. At the same time, the dislocation density of the experimental steel with different rolling pass was calculated. When the thickness reduction is 88%, the dislocation density is the highest, and then the degree of working hardening is the highest. The analysis shows that with the increase of the deformation, the strength increment caused by the strengthening of the second phase and grain refinement shows an increasing trend, while the strength increment caused by dislocation enhancement first increases and then decreases. The main strengthening methods of D6A steel are second phase strengthening, fine grain strengthening and dislocation strengthening.

Keywords

• d6a steel
• second phase strengthening
• fine grain strengthening
• dislocation density
• wh method
• dislocation strengthening