TY - JOUR

T1 - Unusual relationship between impact toughness and grain size in a high-manganese steel

AU - Xie, Pan

AU - Shen, Shucheng

AU - Wu, Cuilan

AU - LI, Jiehua

AU - Chen, Jianghua

N1 - Publisher Copyright: © 2021

PY - 2021/4/13

Y1 - 2021/4/13

N2 - The high-manganese steels are important structural materials, owing to their excellent toughness at low temperatures. However, the microstructural causes for their unusual properties have not adequately been understood thus far. Here, we report a reversal relationship between impact toughness and grain size in a high-manganese steel and its unrevealed microscopic mechanisms, which result in an excellent low-temperature toughness of the steel. Our investigations show that with increasing grain size the impact toughness of the steel can be improved drastically, especially at low-temperatures. Advanced electron microscopy characterization reveals that the enhanced impact toughness of the coarse-grained steel is attributed to the twinning induced plasticity and transformation induced plasticity effects, which produce large quantities of deformation twins, ε hcp-martensite and α′ bcc-martensite. Inversely, in the fine-grained steels, the formation of deformation twins and martensite is significantly inhibited, leading to the decrease of impact toughness. Microstructural characterizations also indicate that ε hcp-martensite becomes more stable than α′ bcc-martensite with decreasing temperature, resulting in characteristic microstructures in the coarse-grained samples after impact deformation at liquid nitrogen temperature. In the coarse-grained samples under impact deformation at -80 °C, ε hcp-martensite transformation, α′ bcc-martensite transformation and deformation twinning all occur simultaneously, which greatly improves the toughness of the steel.

AB - The high-manganese steels are important structural materials, owing to their excellent toughness at low temperatures. However, the microstructural causes for their unusual properties have not adequately been understood thus far. Here, we report a reversal relationship between impact toughness and grain size in a high-manganese steel and its unrevealed microscopic mechanisms, which result in an excellent low-temperature toughness of the steel. Our investigations show that with increasing grain size the impact toughness of the steel can be improved drastically, especially at low-temperatures. Advanced electron microscopy characterization reveals that the enhanced impact toughness of the coarse-grained steel is attributed to the twinning induced plasticity and transformation induced plasticity effects, which produce large quantities of deformation twins, ε hcp-martensite and α′ bcc-martensite. Inversely, in the fine-grained steels, the formation of deformation twins and martensite is significantly inhibited, leading to the decrease of impact toughness. Microstructural characterizations also indicate that ε hcp-martensite becomes more stable than α′ bcc-martensite with decreasing temperature, resulting in characteristic microstructures in the coarse-grained samples after impact deformation at liquid nitrogen temperature. In the coarse-grained samples under impact deformation at -80 °C, ε hcp-martensite transformation, α′ bcc-martensite transformation and deformation twinning all occur simultaneously, which greatly improves the toughness of the steel.

UR - http://www.scopus.com/inward/record.url?scp=85103977863&partnerID=8YFLogxK

U2 - 10.1016/j.jmst.2021.01.089

DO - 10.1016/j.jmst.2021.01.089

M3 - Article

VL - 89.2021

SP - 122

EP - 132

JO - JOURNAL OF MATERIALS SCIENCE & TECHNOLOGY

JF - JOURNAL OF MATERIALS SCIENCE & TECHNOLOGY

SN - 1005-0302

IS - 30 October

ER -