Precipitation strengthening has been widely adopted in austenitic low-density steel owing to excellent hardened effects.This approach generally employs the coherentκ′carbides and non-coherent B2 particles.Revealing ...Precipitation strengthening has been widely adopted in austenitic low-density steel owing to excellent hardened effects.This approach generally employs the coherentκ′carbides and non-coherent B2 particles.Revealing the precipitation transformation pathway is decisive for further optimizing the microstructures under specific engineering applications.Herein,the detailed precipitation sequence of Fe-28Mn-11Al-1C-5Ni(wt%)austenitic low-density steel as well as its influence on mechanical prop-erties during aging process is systematically investigated.Our results reveal that nano-sizedκ′carbides domains(2 nm)exist in the solution-treated specimen.During aging at 500℃for 1 h,the cuboidalκ′carbides(15-20 nm)uniformly disperse in austenite matrix.However,after aging at 700℃for 15 min,the coarsenκ′carbides(30-35 nm)inhomogeneously distribute and align preferentially along the〈100〉directions.Further,extending the aging time to 60 min,the needle-type B2 particles replace theκ′carbides due to the enrichment of Ni elements at the phase boundaries among the austenite andκ′carbides.After aging at 900℃,κ′carbides entirely dissolve into the austenite matrix,and the intragranular B2 particles are the sole precipitates in the austenite matrix and follow the K-S orientation relationship with austenite.The work hardening capability seriously deteriorates due to the shearing ofκ′carbides by gliding dislocations.While the intragranular B2 particles preserve excellent work hardening rate by dislocations bow-out mechanism.The present work is meaningful for guiding the design of new generation dual-nano precipitation austenitic lightweight steel.展开更多
基金supported by the National Natural Science Foundation of China(Nos.52171105 and 51871062).
文摘Precipitation strengthening has been widely adopted in austenitic low-density steel owing to excellent hardened effects.This approach generally employs the coherentκ′carbides and non-coherent B2 particles.Revealing the precipitation transformation pathway is decisive for further optimizing the microstructures under specific engineering applications.Herein,the detailed precipitation sequence of Fe-28Mn-11Al-1C-5Ni(wt%)austenitic low-density steel as well as its influence on mechanical prop-erties during aging process is systematically investigated.Our results reveal that nano-sizedκ′carbides domains(2 nm)exist in the solution-treated specimen.During aging at 500℃for 1 h,the cuboidalκ′carbides(15-20 nm)uniformly disperse in austenite matrix.However,after aging at 700℃for 15 min,the coarsenκ′carbides(30-35 nm)inhomogeneously distribute and align preferentially along the〈100〉directions.Further,extending the aging time to 60 min,the needle-type B2 particles replace theκ′carbides due to the enrichment of Ni elements at the phase boundaries among the austenite andκ′carbides.After aging at 900℃,κ′carbides entirely dissolve into the austenite matrix,and the intragranular B2 particles are the sole precipitates in the austenite matrix and follow the K-S orientation relationship with austenite.The work hardening capability seriously deteriorates due to the shearing ofκ′carbides by gliding dislocations.While the intragranular B2 particles preserve excellent work hardening rate by dislocations bow-out mechanism.The present work is meaningful for guiding the design of new generation dual-nano precipitation austenitic lightweight steel.
