Effect of Warm to Hot Rolling on Microstructure, Texture and Mechanical Properties of an Advanced Medium-Mn Steel

Abstract

The deformation microstructures and mechanical properties were studied in a medium-Mn austenitic steel subjected to warm-to-hot rolling. During warm rolling at temperatures of T < 1073 K the structural changes were controlled by dynamic and static recovery leading to a pancaked work-hardened microstructure, during hot rolling at T ‡ 1073 K-by discontinuous dynamic and post-dynamic recrystallization resulting in equiaxed grains. The grain size decreased while the dislocation density increased with a decrease in rolling temperature. A decrease in rolling temperature enhanced the texture development, which consisted of relatively strong Brass, S and P components. The Brass component exhibited the strongest temperature dependence. A decrease in rolling temperature resulted in significant strengthening of the steel. The yield strength increased from 340 to 950 MPa as rolling temperature decreased from 1373 K to 773 K. Both the grain refinement and the work-hardening contributed to the strengthening.

Hot Deformation and Dynamic Recrystallization of 18%Mn Twinning‐Induced Plasticity Steels

“…The present DRX grain size can be expressed by a power law function of Z with an exponent of −0.25 in the range of Z < 13 13 s −1 corresponding to hot‐working conditions. Almost the same results with the exponents of −0.3 to 0.4 were reported in other studies on DRX in austenite . The change in the strong temperature/strain rate dependence of the DRX grain size to much weaker one at Z > 10 13 s −1 in Figure clearly corresponds to similar change in the temperature/strain rate dependence of the peak flow stress in Figure , suggesting the transition from hot‐working to warm‐working conditions.…”

“…Relationship between the DRX grain size and temperature‐compensated strain rate ( Z ) for the present Fe–0.4C–18Mn and Fe–0.6C–18Mn steels, and other austenitic steels …”

“…[23] The operation of continuous DRX has been frequently observed in low-to-medium SFE fcc alloys under conditions of warm working. [12,[36][37][38] The rapid development of strain-induced high-angle boundaries in deformation microshear bands and close to original grain boundaries has been shown to result in a characteristic necklace microstructure. [46] Therefore, continuous DRX development could be expected in the present steels at 973 K (Figure 12a,d).…”

“…The present DRX grain size was evaluated in the portions of microstructure with GOS below 4 . The DRX data for other austenitic steels [36][37][38] are also shown in Figure 10 for reference. The present DRX grain size can be expressed by a power law function of Z with an exponent of À0.25 in the range of Z < 13 13 s À1 corresponding to hot-working conditions.…”

“…Relationship between the DRX grain size and temperaturecompensated strain rate (Z ) for the present Fe-0.4C-18Mn and Fe-0.6C-18Mn steels, and other austenitic steels. [36][37][38] Figure 11. IPFs for the CA for the a-c) Fe-0.4C-18Mn and d-f ) Fe-0.6C-18Mn steel samples subjected to hot compressions at a,d) T ¼ 973 K anḋ ε ¼ 10 À1 s À1 , b,e) T ¼ 1173 K andε ¼ 10 À1 s À1 , and c,f ) T ¼ 1273 K andε ¼ 10 À3 s À1 .…”