Although magnesium-aluminum alloys,such as AZ80 and AZ91 have promising application potential in automotive,high-speed train and aerospace fields,their age-hardening response is generally not very appreciable.In this ...Although magnesium-aluminum alloys,such as AZ80 and AZ91 have promising application potential in automotive,high-speed train and aerospace fields,their age-hardening response is generally not very appreciable.In this work,the aging-hardening response of AZ80 alloy was effectively enhanced by applying cold-rolling deformation before conducting conventional aging treatment at 200°C.Compared to the directly aged sample,the yield strength of the pre-rolling and aged sample was increased by 35 MPa.Electron microscope examination confirmed that profuse{10¯11}and{10¯11}-{10¯12}twins,consisting of high density of dislocations and stacking faults,were generated by cold rolling.Blocky or ellipsoidal Mg_(17)Al_(12)precipitates formed at the twin boundaries(TBs)during subsequent aging treatment.Crystallographic analysis indicated that the precipitates at{10¯11}TBs always held an identical Potter OR with both the matrix and twin,while the precipitates at{10¯11}-{10¯12}TBs exhibited three different ORs:Burgers OR,Potter OR and P-S OR with either the matrix or the twin.Moreover,recrystallized grains were found inside{10¯11}-{10¯12}double twins after peak-aging at 200°C,implying that precipitation and recrystallization might occur concurrently along TBs at a relatively low temperature.It was speculated that the highly stored energy inside twins and the high elastic energy between the precipitates and twins were driving factors for the occurrence of recrystallization.展开更多
To improve the tribocorrosion resistance of oil drill pipes used in deep-sea drilling,a Ti-based composite coating was successfully fabricated by laser direct energy deposition technology on the TC4 titanium alloy sur...To improve the tribocorrosion resistance of oil drill pipes used in deep-sea drilling,a Ti-based composite coating was successfully fabricated by laser direct energy deposition technology on the TC4 titanium alloy surface.The microstructure analysis showed that a new heterogeneous structure of multistage strength-ening phases(micron-sized TiN phases and nano-sized TiB phases)distributed on theβmatrix(soft Cu-rich phases and hard Mo-rich phases)was formed,and the size ofβgrain was refined to 2μm with the content of Cu higher than 12 wt.%.The microhardness of the composite coating was increased to more than 700 HV_(0.2)due to the solution strengthening of Mo elements and the formation of hard TiN phases.At the same time,the fracture toughness of 12Cu composite coating was significantly increased to 8.37 MPa m^(1/2),which was attributed to the combined effect of grain refining,high-density dislocations in Cu-rich phases,and nanoscale TiB phases.The synergistic enhancement of hardness and toughness of 12Cu composite coating promoted the generation of titano-molybdenum-copper composite oxide film on the worn surface,and the tribocorrosion resistance increased more than 7 times compared with TC4.展开更多
Electron backscatter diffraction(EBSD)is an orientation mapping technique,which has been widely used to study texture evolution and twinning behavior.This work aims to study the variant of{10¯12}twins during tens...Electron backscatter diffraction(EBSD)is an orientation mapping technique,which has been widely used to study texture evolution and twinning behavior.This work aims to study the variant of{10¯12}twins during tensile deformation of AZ31 Mg alloys.An in-situ tensile stage was used,and coupled with EBSD technique,the variants of twins can be analyzed without releasing the tensile stress.Based on the EBSD maps,the first and second smallest misorientation angles(M_(1)and M 2)between each active twin and respective potential variants were calculated,and the distribution of M_(1)values with tensile strain was obtained.The results indicated that{10¯12}twins were deviated from their ideal orientations with strain increased.The criteria of M_(1)<4°and M 2−M_(1)>2°were suggested to be applied to select the data points for reliable variant identification.Moreover,it confirmed that the deviation of twin relationship was ascribed to the profuse basal glide in matrices and/or twins.展开更多
Although the non-basal precipitates, those not parallel to the basal plane, are more effective to block basal slip in Mg-Al alloys, the crystallographic orientation relationship(OR) between these precipitates and the ...Although the non-basal precipitates, those not parallel to the basal plane, are more effective to block basal slip in Mg-Al alloys, the crystallographic orientation relationship(OR) between these precipitates and the α-Mg matrix has not been well established. In this work, the crystallography of the non-basal Mg_(17)Al_(12) precipitates in AZ80 alloy was systematically investigated by transmission electron microscopy(TEM). By tilting to a suitable electron beam direction, different kinds of non-basal precipitates were recognized in TEM, and the following four new ORs between the non-basal Mg_(17)Al_(12) precipitates and the matrix were revealed: ■, and ■.Furthermore, these ORs and their habit planes were explained using the edge-to-edge matching model. The findings in this work can provide some guidelines for designing the microstructure of Mg-Al alloys to enhance their precipitation hardening potential.展开更多
基金financially supported by the National Natural Science Foundation of China(No.52071040 and 51871036)Natural Science Foundation of Shandong Province,China(No.ZR2022QE008)China Postdoctoral Science Foundation(No.2022M712984)。
文摘Although magnesium-aluminum alloys,such as AZ80 and AZ91 have promising application potential in automotive,high-speed train and aerospace fields,their age-hardening response is generally not very appreciable.In this work,the aging-hardening response of AZ80 alloy was effectively enhanced by applying cold-rolling deformation before conducting conventional aging treatment at 200°C.Compared to the directly aged sample,the yield strength of the pre-rolling and aged sample was increased by 35 MPa.Electron microscope examination confirmed that profuse{10¯11}and{10¯11}-{10¯12}twins,consisting of high density of dislocations and stacking faults,were generated by cold rolling.Blocky or ellipsoidal Mg_(17)Al_(12)precipitates formed at the twin boundaries(TBs)during subsequent aging treatment.Crystallographic analysis indicated that the precipitates at{10¯11}TBs always held an identical Potter OR with both the matrix and twin,while the precipitates at{10¯11}-{10¯12}TBs exhibited three different ORs:Burgers OR,Potter OR and P-S OR with either the matrix or the twin.Moreover,recrystallized grains were found inside{10¯11}-{10¯12}double twins after peak-aging at 200°C,implying that precipitation and recrystallization might occur concurrently along TBs at a relatively low temperature.It was speculated that the highly stored energy inside twins and the high elastic energy between the precipitates and twins were driving factors for the occurrence of recrystallization.
基金supported by the National Natural Science Foundation of China-Shandong Joint Fund for Marine Science Research Centers(CN)(No.U2106216)the National Natural Science Foundation of China(Nos.51971121 and 52331004)+4 种基金the Natural Science Foundation of Shandong Province(No.ZR2022ZD12)the Major-Special Science and Technology Projects in Shandong Province(No.2023ZLGX05)the Qingdao Marine Science and Technology Innovation Project(No.22-3-3-hygg-27-hy)the Key Research and Development Program of Shandong Province(No.2020CXGC010305)the Fundamental Research Funds for the Central Universities(Nos.202261105,202141027,202241012,202262011).
文摘To improve the tribocorrosion resistance of oil drill pipes used in deep-sea drilling,a Ti-based composite coating was successfully fabricated by laser direct energy deposition technology on the TC4 titanium alloy surface.The microstructure analysis showed that a new heterogeneous structure of multistage strength-ening phases(micron-sized TiN phases and nano-sized TiB phases)distributed on theβmatrix(soft Cu-rich phases and hard Mo-rich phases)was formed,and the size ofβgrain was refined to 2μm with the content of Cu higher than 12 wt.%.The microhardness of the composite coating was increased to more than 700 HV_(0.2)due to the solution strengthening of Mo elements and the formation of hard TiN phases.At the same time,the fracture toughness of 12Cu composite coating was significantly increased to 8.37 MPa m^(1/2),which was attributed to the combined effect of grain refining,high-density dislocations in Cu-rich phases,and nanoscale TiB phases.The synergistic enhancement of hardness and toughness of 12Cu composite coating promoted the generation of titano-molybdenum-copper composite oxide film on the worn surface,and the tribocorrosion resistance increased more than 7 times compared with TC4.
基金RL Xin would like to thank Prof.John J.Jonas for his helpful comments.This project was financially supported by the National Natural Science Foundation of China(Project no.51571045,51471039 and 51421001)Zhejiang Provincial Natural Science Foundation of China(LQ18E010004).
文摘Electron backscatter diffraction(EBSD)is an orientation mapping technique,which has been widely used to study texture evolution and twinning behavior.This work aims to study the variant of{10¯12}twins during tensile deformation of AZ31 Mg alloys.An in-situ tensile stage was used,and coupled with EBSD technique,the variants of twins can be analyzed without releasing the tensile stress.Based on the EBSD maps,the first and second smallest misorientation angles(M_(1)and M 2)between each active twin and respective potential variants were calculated,and the distribution of M_(1)values with tensile strain was obtained.The results indicated that{10¯12}twins were deviated from their ideal orientations with strain increased.The criteria of M_(1)<4°and M 2−M_(1)>2°were suggested to be applied to select the data points for reliable variant identification.Moreover,it confirmed that the deviation of twin relationship was ascribed to the profuse basal glide in matrices and/or twins.
基金financially supported by the National Natural Science Foundation of China (Project No.51871036,52071040 and 51421001)the open funding of International Joint Laboratory for Light Alloys (MOE),Chongqing University。
文摘Although the non-basal precipitates, those not parallel to the basal plane, are more effective to block basal slip in Mg-Al alloys, the crystallographic orientation relationship(OR) between these precipitates and the α-Mg matrix has not been well established. In this work, the crystallography of the non-basal Mg_(17)Al_(12) precipitates in AZ80 alloy was systematically investigated by transmission electron microscopy(TEM). By tilting to a suitable electron beam direction, different kinds of non-basal precipitates were recognized in TEM, and the following four new ORs between the non-basal Mg_(17)Al_(12) precipitates and the matrix were revealed: ■, and ■.Furthermore, these ORs and their habit planes were explained using the edge-to-edge matching model. The findings in this work can provide some guidelines for designing the microstructure of Mg-Al alloys to enhance their precipitation hardening potential.
