Crystallographic texture evolution and martensite transformation in the strain hardening process of a ferrite-based low density steel

The strain-induced martensite transformation is of great importance in the strain hardening process of ferrite based low-density steel. Based on the microstructure analysis, the texture evolution and martensite transformation behavior in the strain hardening process were studied. The results show that martensite transformation accompanied by TWIP effect and high density dislocations maintains the continuous hardening stage. As the strain increases, the texture of retained austenite evolves towards the F orientation {111}<112>, which is not conducive to martensite transformation. After the strain of 5%, the number of austenite grains with high Schmid factor orientations is gradually increased, and then significantly reduced when the strain is over 10 % due to the occurrence of martensitic transformation, which results in a high martensitic transformation rate. However, the unfavorable orientation and the reduced grain size of austenite slow down the martensite transformation at the final hardening stage. Moreover, because of the coordination deformation of austenite grains, strain preferentially spreads between adjacent austenite grains. Consequently, the martensite transformation rate in strain hardening process is dependent on the orientation and grain size evolution of austenite, leading to a differential contribution to each strain hardening stage. (C) 2021 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.

Automated summary

The strain-induced martensite transformation plays a crucial role in the strain hardening process of low-density steel. This transformation is affected by the texture evolution and grain size of austenite, influencing the rate of martensite transformation in each stage of strain hardening. The presence of TWIP effect and high density dislocations during martensite transformation contributes to continuous hardening, but the final stage is slowed down by unfavorable orientation and reduced grain size of austenite.