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
The initial-stage oxidation behaviours of unmodified,Pt and Pt+Hf modified NiAl coating are systematically investigated by employing the photo-stimulated luminescence spectroscopy(PSLS)and transmission electron micros...The initial-stage oxidation behaviours of unmodified,Pt and Pt+Hf modified NiAl coating are systematically investigated by employing the photo-stimulated luminescence spectroscopy(PSLS)and transmission electron microscopy(TEM)technique.Both Pt and Hf additions can retard the θ-toα-Al_(2)O_(3)phase transformation.The oxidation rates of the modified NiAl coatings are initially higher than that of the unmodified NiAl coating due to the longer presence of θ-Al_(2)O_(3).However,they decrease drastically when the oxide in the scale turns to be α-Al_(2)O_(3)dominantly.The delayed phase transformation in the modified coatings results in lower residual stress within the oxide scale.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.
基金financially supported by Science and Technology Program of Guangzhou(No.202007020008)the National Natural Science Foundation of China(No.52001137)+2 种基金the Guangdong Academy of Sciences Program(No.2020GDASYL-20200104028)the Natural Science Foundation of Guangdong Province(No.2020A1515010948)the Guang Dong Basic and Applied Basic Research Foundation(No.2021A1515111065)
文摘The initial-stage oxidation behaviours of unmodified,Pt and Pt+Hf modified NiAl coating are systematically investigated by employing the photo-stimulated luminescence spectroscopy(PSLS)and transmission electron microscopy(TEM)technique.Both Pt and Hf additions can retard the θ-toα-Al_(2)O_(3)phase transformation.The oxidation rates of the modified NiAl coatings are initially higher than that of the unmodified NiAl coating due to the longer presence of θ-Al_(2)O_(3).However,they decrease drastically when the oxide in the scale turns to be α-Al_(2)O_(3)dominantly.The delayed phase transformation in the modified coatings results in lower residual stress within the oxide scale.
