Cryogenic toughness in a low-cost austenitic steel

Abstract

At low temperatures most metals show reduced ductility and impact toughness. Here, we report a compositionally lean, fine-grained Fe-30Mn-0.11C austenitic steel that breaks this rule, exhibiting an increase in strength, elongation and Charpy impact toughness with decreasing temperature. A Charpy impact energy of 453 J is achieved at liquid nitrogen temperatures, which is about four to five times that of conventional cryogenic austenitic steels. The high toughness is attributed to manganese and carbon austenite stabilizing elements, coupled with a reduction in grain size to the near-micrometer scale. Under these conditions dislocation slip and deformation twinning are the main deformation mechanisms, while embrittlement by α′- and ε-martensite transformations are inhibited. This reduces local stress and strain concentration, thereby retarding crack nucleation and prolonging work-hardening. The alloy is low-cost and can be processed by conventional production processes, making it suitable for low-temperature applications in industry.

Tailoring the Microstructure to Enhance the Cryogenic Mechanical Properties of a Fe–34.5mn–0.04c Steel

“…The slightly higher C content in the Fe-30Mn-0.11C steel may therefore ensure more sustained work hardening, avoiding at the same time the development of stress concentrations. An important consequence of this is that higher internal stresses, with values exceeding the onset stress for deformation twinning, can be reached in the Fe-30Mn-0.11C steel before fracture [14,37]. It can be noted here that such mechanical twinning can further enhance the work hardening ability, through the so-called dynamic Hall-Petch effect, which in turn increases the material ductility.…”

Microstructure Evolution and Tensile Properties of Cold-Rolled and Annealed Fe-30Mn-0.14C-7Cr-0.26Ni Steel

“…The carbide particles stimulate more nuclei and hinder the growth of grains [26,36]. Consequently, the recrystallization level and grain size of the experimental steel after cold rolling to 95% reduction followed by annealing were much smaller than those of other high-manganese steels without particles annealed at similar temperatures [42,43].…”

Heterogeneous lamellar-structured high manganese steel with excellent tensile properties

“…Subsequently, the samples were waterquenched. The Fe-30Mn-0.11C steel has a stable austenitic structure after 90% cold rolling, which was characterized in our previous work [17][18].…”