Heterogeneous microstructures of martensite and pearlite achieving excellent mechanical properties in high carbon chromium steel by multi-cycle flash heating treatment

Abstract

Traditional homogeneous microstructures such as martensite, bainite, and pearlite struggle to balance strength and ductility in high carbon chromium steels. This study introduces a novel approach to achieving strength-ductility synergy by developing heterogeneous microstructures of martensite and pearlite during the continuous cooling transformation of supercooled austenite. By applying flash heating treatment, we achieved austenite chemical heterogenization and retained some undissolved carbides. We controlled the heating rate and the number of cycles to allow the pearlite volume fraction to vary between 24.8 % and 59.7 %. The samples subjected to multi-cycle flash heating exhibited fine grain sizes (1.08 μm) and higher dislocation densities, attaining a yield strength of 1294 MPa, an ultimate tensile strength of 1605 MPa and an elongation of 9.8 %. The enhanced mechanical properties were primarily attributed to dislocation hardening, grain refinement, and hetero-deformation-induced stress resulting from the coexistence of martensite and pearlite phases. This study provides a new strategy for optimizing the mechanical properties of high carbon chromium steels and provides valuable insights for advancing the development of other materials with excellent mechanical properties.