Precipitation strengthening of nano-scale TiC in a duplex low-density steel under near-rapid solidification
Résumé
Precipitation strengthening of nano-scale TiC is a promising method to improve mechanical properties of Fe–16Mn–9Al–0.8C (wt.%) low-density steel. This work attempted to introduce nano-scale TiC precipitates by adding 1 wt.% Ti element. The experimental results show that these precipitates with the total fraction of about 2 vol.% were formed and no coarse precipitates were observed despite the high Ti addition. It was interesting that the polygonal and needle-shaped TiC precipitates were observed in γ-austenite and δ-ferrite, respectively. Ti addition also decreased the volume fraction of γ-austenite significantly. Correspondingly, the yield strength was increased, but the elongation was significantly decreased due to the significant decrease of γ-austenite. Comparing with the Ti-free steel, the formation of TiC precipitates was the main reason for the increase in yield strength of Ti-bearing steel, and TiC precipitates also led to a higher strain hardening index at the first deformation stage. TiC precipitates promoted the Orowan strengthening, resulting in a higher strain hardening capability than Ti-free steel reinforced by shearable κ-carbide.