In order to study the application of gas fire extinguishing agents in civil aircraft fire extinguishing systems,the corrosion characteristics and mechanisms of Halon 1301 and CF_(3)I on AZ80A magnesium alloy were comp...In order to study the application of gas fire extinguishing agents in civil aircraft fire extinguishing systems,the corrosion characteristics and mechanisms of Halon 1301 and CF_(3)I on AZ80A magnesium alloy were comparatively analyzed.The experimental methods combined with density functional theory were applied to explore the corrosion mechanism.The results indicate that Halon 1301 and CF_(3)I exhibit good compatibility with AZ80A magnesium alloy through physical adsorption at room temperature and pressure,where Halon 1301 has a more stable adsorption configuration.However,with increasing temperature,pyrolysis reactions occur leading to the formation of fluorine containing corrosive substances which can react with magnesium alloy to generate the corrosion production of MgF_(2) and coke.Although MgF_(2) and coke can partically reduce reaction rates and protect against corrosion,the presence of MgF_(2) promotes further pyrolysis,generating more corrosion products.Consequently,the accumulation of corrosion products leads to a loss of metallic luster and a decline in mechanical properties of magnesium alloy along with interfacial cracking due to mutual extrusion between MgF_(2) and carbon deposition layers.These studies offer theoretical guidance for utilizing CF_(3)I in civil aircraft fire extinguishing systems while facilitating rapid screening for efficient clean gas extinguishing agents.展开更多
Mechanism of discontinuous precipitation(DP) in AZ80 alloy was investigated by phase-orientation correlated characterization.The results show DPs nucleate by turning the original grain boundaries(GBs) as reaction fron...Mechanism of discontinuous precipitation(DP) in AZ80 alloy was investigated by phase-orientation correlated characterization.The results show DPs nucleate by turning the original grain boundaries(GBs) as reaction front(RF),and further driving the RF to realize their growth.The DPs regions retained the same orientations as their parent grains.The misorientation angle and rotation axis of RFs had strong influence on DPs nucleation.The low-angle GBs,twin boundaries(TBs) and the GBs with specific misorientation axis which are known as low energy and low mobility GBs can hardly initiate DPs.In addition,the TBs had a strong ability to inhibit the growth of DPs,but it should be noticed that the growth of DPs cannot be totally inhibited by TBs.DPs can engulf the twins when the growth direction is approximately parallel to the long axis of TBs.The inhibition behavior is related to the distribution of Al solute atoms near the RF,boundary interactions of the TBs and twin tips with the RF,and the morphology of the continuous precipitations within the twins.展开更多
This work presents the modified precipitation behavior of the β phase in a Mg-8.0Al-0.5Zn-0.2Mn-0.4Ce alloy(wt%,designated as AZ80+0.4%Ce),which has been subjected to room-temperature pre-compression and a subsequent...This work presents the modified precipitation behavior of the β phase in a Mg-8.0Al-0.5Zn-0.2Mn-0.4Ce alloy(wt%,designated as AZ80+0.4%Ce),which has been subjected to room-temperature pre-compression and a subsequent dual-stage aging treatment,thereby imparting it with the pronounced basal texture.It was found that the synergistic application of pre-compression and dual-stage aging protocol markedly accelerates the age-hardening response and architecture of the continuous precipitates(CPs)in the present AZ80+0.4%Ce alloy.Consequently,this alloy achieves an exceptional balance between strength and ductility,boasting a yield strength of approximately 229.0 MPa alongside an elongation of around 7.0%.A series of microstructural characterizations reveal that high-density intragranular dislocations introduced by pre-compression serve as catalysts for the preferential formation of CPs over the discontinuous precipitates,effectively suppressing the latter.Notably,this also facilitates static recrystallization,which refines the grain structure and alleviates the residual stresses induced by deformation,further enhancing the mechanical properties.This research contributes a novel perspective to the thermomechanical processing design of precipitation-hardened lightweight alloys,offering a pathway to optimize their performance through tailored thermomechanical strategies.展开更多
基金supported by the Joint Funds of the National Natural Science Foundation of China“False alarm immunity fire detection mechanism and key technologies of civil aviation aircraft cargo compartment”[Grant No.U213320003]Science and Technology Program of Tianjin“Research on fire characteristics and advanced halo-carbon fire extinguishing technology of domestic civil aircraft”[Grant No.21JCZDJC00810].
文摘In order to study the application of gas fire extinguishing agents in civil aircraft fire extinguishing systems,the corrosion characteristics and mechanisms of Halon 1301 and CF_(3)I on AZ80A magnesium alloy were comparatively analyzed.The experimental methods combined with density functional theory were applied to explore the corrosion mechanism.The results indicate that Halon 1301 and CF_(3)I exhibit good compatibility with AZ80A magnesium alloy through physical adsorption at room temperature and pressure,where Halon 1301 has a more stable adsorption configuration.However,with increasing temperature,pyrolysis reactions occur leading to the formation of fluorine containing corrosive substances which can react with magnesium alloy to generate the corrosion production of MgF_(2) and coke.Although MgF_(2) and coke can partically reduce reaction rates and protect against corrosion,the presence of MgF_(2) promotes further pyrolysis,generating more corrosion products.Consequently,the accumulation of corrosion products leads to a loss of metallic luster and a decline in mechanical properties of magnesium alloy along with interfacial cracking due to mutual extrusion between MgF_(2) and carbon deposition layers.These studies offer theoretical guidance for utilizing CF_(3)I in civil aircraft fire extinguishing systems while facilitating rapid screening for efficient clean gas extinguishing agents.
基金supported by National Natural Science Foundation of China (52201107)Research Program of Chongqing Municipal Education Commission (KJQN202201151)Natural Science Foundation of Chongqing (CSTB2023NSCQ-MSX0067).
文摘Mechanism of discontinuous precipitation(DP) in AZ80 alloy was investigated by phase-orientation correlated characterization.The results show DPs nucleate by turning the original grain boundaries(GBs) as reaction front(RF),and further driving the RF to realize their growth.The DPs regions retained the same orientations as their parent grains.The misorientation angle and rotation axis of RFs had strong influence on DPs nucleation.The low-angle GBs,twin boundaries(TBs) and the GBs with specific misorientation axis which are known as low energy and low mobility GBs can hardly initiate DPs.In addition,the TBs had a strong ability to inhibit the growth of DPs,but it should be noticed that the growth of DPs cannot be totally inhibited by TBs.DPs can engulf the twins when the growth direction is approximately parallel to the long axis of TBs.The inhibition behavior is related to the distribution of Al solute atoms near the RF,boundary interactions of the TBs and twin tips with the RF,and the morphology of the continuous precipitations within the twins.
基金supported by the Innovative Talents Support Program of Higher Education Institutions in Shanxi Province and the North University of China Project of Science and Technology in 2022(20221878).
文摘This work presents the modified precipitation behavior of the β phase in a Mg-8.0Al-0.5Zn-0.2Mn-0.4Ce alloy(wt%,designated as AZ80+0.4%Ce),which has been subjected to room-temperature pre-compression and a subsequent dual-stage aging treatment,thereby imparting it with the pronounced basal texture.It was found that the synergistic application of pre-compression and dual-stage aging protocol markedly accelerates the age-hardening response and architecture of the continuous precipitates(CPs)in the present AZ80+0.4%Ce alloy.Consequently,this alloy achieves an exceptional balance between strength and ductility,boasting a yield strength of approximately 229.0 MPa alongside an elongation of around 7.0%.A series of microstructural characterizations reveal that high-density intragranular dislocations introduced by pre-compression serve as catalysts for the preferential formation of CPs over the discontinuous precipitates,effectively suppressing the latter.Notably,this also facilitates static recrystallization,which refines the grain structure and alleviates the residual stresses induced by deformation,further enhancing the mechanical properties.This research contributes a novel perspective to the thermomechanical processing design of precipitation-hardened lightweight alloys,offering a pathway to optimize their performance through tailored thermomechanical strategies.
