Research progress toward hydrogen embrittlement microstructure mechanism in Fe–Mn–(Al)–C high-strength-and-toughness steel

Abstract

With the rapid development of the automobile industry, the development and application of lightweight automobile steel are increasingly extensive. The second- and third-generation automobile steels with a tensile strength of over 1000 MPa are usually of duplex structure. Through solid solution strengthening, precipitation, deformation, fine grain strengthening, and other strengthening methods, a large number of defects are formed in the matrix, which makes the steel more sensitive to hydrogen in the service process and prone to hydrogen embrittlement under very small hydrogen dissolution conditions. The high-Mn content steels Fe−Mn−C and Fe−Mn−Al−C steels have high stacking fault energy, which not only influences their strength and toughness but also significantly affects their service performance. Based on the composition of twinning-induced plasticity (TWIP) steel of the Fe−Mn−C system, adding a small amount of Al element to form Fe−Mn−(Al)−C steel can not only reduce the steel density and improve the steel strength and toughness but also change the steel microstructure to a certain extent; the effect on the microstructure reduces the steel susceptibility to hydrogen embrittlement. However, when the Al content is high, low-density steel with a more complex structure is formed, and the precipitates are more, which leads to a more significant sensitivity to hydrogen embrittlement. In this paper, the permeation, dissolution, and diffusion behavior of H in Fe−Mn−(Al)−C high-strength-and-toughness-steel; the interaction between H and the matrix structure, the precipitated phase, and lattice defects; the model of H in steel; the hydrogen embrittlement mechanism; and the methods of hydrogen embrittlement evaluation were summarized based on the structure, second phase, and crystal defects of Fe−Mn−(Al)−C high-strength-and-toughness steel. The related research work and the latest developments of the hydrogen embrittlement of Fe−Mn−(Al)−C high-strength-and-toughness steel were reviewed. The development direction of the hydrogen embrittlement microstructure mechanism of high-strength-and-toughness steel was revealed by combining first-principle calculations, molecular dynamics simulation, and physical experiments such as hydrogen atom microprinting technology and three-dimensional atomic probe analysis.

Keywords

• low-density steel
• twinning-induced plasticity
• hydrogen embrittlement
• lattice defect
• microstructure mechanism