Enhancement of strength and ductility of Fe-13Al-16Mn-5Ni-0.8C steel by annealing at high temperature

The mechanical properties and microstructural evolution of low-density (6.89 g/cm(3)) steel having composition of Fe-13Al-16Mn-5Ni-0.8C has been investigated after annealing at 720 & DEG;C and 1050 & DEG;C, respectively. At 720 & DEG;C, nanosized B-2-particles of different morphologies were formed inside austenite and ferrite grains. After annealing at 1050 & DEG;C the selected area diffraction (SAED) and HAADF analysis confirmed the formation of rod-shaped ordered Ni3Al-type particles of FCC crystal structure on the (111) plane of austenite grains. Moreover, inside the ferrite grains, new austenite grains up to 30 mu m in size were observed. Ordered Ni3Al-type rod and spherical shape particles contributed to an increase of 7% in the average ultimate tensile strength due to hindering of dislocations movement on the active slip plane of austenite grains. A significant increase of 233% in average elongation to failure was also achieved with high-temperature annealing due to the evolution of new austenite grains and the disappearance of B-2 particles. The presence of fibrous dimple fracture in the sample annealed at 1050 & DEG;C is consistent with the high ductility observed. This is in stark comparison to the sample annealed at 720 & DEG;C which showed failure through ductile tearing and cleavage.

Automated summary

The mechanical properties and microstructural evolution of low-density steel were investigated after annealing at different temperatures. The formation of ordered Ni3Al-type particles and new austenite grains contributed to an increase in ultimate tensile strength and elongation to failure.