Strength-ductility trade-off is usually an inevitable scenario inκ′-carbides strengthened austenitic lightweight steel.The reduction of ductility is primarily attributed to the shearing of coherentκ′-carbides by d...Strength-ductility trade-off is usually an inevitable scenario inκ′-carbides strengthened austenitic lightweight steel.The reduction of ductility is primarily attributed to the shearing of coherentκ′-carbides by dislocations,resulting in strain localization and ultimately leading to a low work hardening rate.Semicoherent B2 particles,on the other hand,effectively enhance the work hardening capability due to the non-shearable feature.However,achieving a large volume fraction and uniform distribution of B2 particles within the austenite matrix,as well as optimizing their morphology as fine particles,remains a challenge for austenitic lightweight steel.In this study,we have addressed the above challenges by implementing the two-step aging process combined with pre-cold rolling process.The pre-cold rolling treatment,performed prior to the initial aging treatment at 900℃,effectively promotes the heterogeneous nucleation of B2 particles by introducing dislocations,resulting in a more uniform distribution of B2 particles and a refinement in size(with an average length of 200–500 nm and a width of 50–80 nm).Furthermore,these intragranular B2 particles exhibit the typical K-S and N-W orientation relationships with the austenite matrix.Subsequently,after the second-step aging process at 450℃,spherical nano-sizedκ′-carbides(5 nm)are homogeneously dispersed within the austenite matrix.The above dual nanoparticles provide an approximate precipitation hardening effect of 400 MPa.Concurrently,the nanoscale“planar slip and dislocation bow-out”multiple deformation mechanisms contribute to an efficient source of work hardening capability,leading to a beneficial synergy of strength-ductility.This promising strategy is expected to expand the applications of dual-nanoprecipitation austenitic low-density steel in various lightweight structural materials.展开更多
基金supported by the National Natural Science Foundation of China(Nos.52171105 and 51871062).
文摘Strength-ductility trade-off is usually an inevitable scenario inκ′-carbides strengthened austenitic lightweight steel.The reduction of ductility is primarily attributed to the shearing of coherentκ′-carbides by dislocations,resulting in strain localization and ultimately leading to a low work hardening rate.Semicoherent B2 particles,on the other hand,effectively enhance the work hardening capability due to the non-shearable feature.However,achieving a large volume fraction and uniform distribution of B2 particles within the austenite matrix,as well as optimizing their morphology as fine particles,remains a challenge for austenitic lightweight steel.In this study,we have addressed the above challenges by implementing the two-step aging process combined with pre-cold rolling process.The pre-cold rolling treatment,performed prior to the initial aging treatment at 900℃,effectively promotes the heterogeneous nucleation of B2 particles by introducing dislocations,resulting in a more uniform distribution of B2 particles and a refinement in size(with an average length of 200–500 nm and a width of 50–80 nm).Furthermore,these intragranular B2 particles exhibit the typical K-S and N-W orientation relationships with the austenite matrix.Subsequently,after the second-step aging process at 450℃,spherical nano-sizedκ′-carbides(5 nm)are homogeneously dispersed within the austenite matrix.The above dual nanoparticles provide an approximate precipitation hardening effect of 400 MPa.Concurrently,the nanoscale“planar slip and dislocation bow-out”multiple deformation mechanisms contribute to an efficient source of work hardening capability,leading to a beneficial synergy of strength-ductility.This promising strategy is expected to expand the applications of dual-nanoprecipitation austenitic low-density steel in various lightweight structural materials.
