<i>Supporting data for “Microstructure and deformation mechanisms of ultrahigh-strength high-alloyed medium-carbon steel”</i>

Ultrastrong steel with a martensite matrix typically possesses limited uniform elongation due to lacking plastic carriers. Carbon, a strong contributor to strength, can deteriorate the ductility of the steel as its content increases. The decrease in ductility is generally attributed to a crystal structural evolution from a cubic structure to a tetragonal structure, which reduces dislocation slip systems. However, in the present thesis, high internal stress in medium or high-carbon martensite, rather than the body-centred tetragonal (BCT) lattice itself, is speculated as the primary cause of the brittleness in ultrahigh-strength steel with a martensite matrix. Based on this hypothesis, a new high-alloyed medium-carbon steel was developed. Microstructure and deformation mechanisms of this developed steel are systematically investigated.