Near-αtitanium alloy and Ti_(2)AlNb alloy powders premixed with different proportions were prepared on the near-αtitanium alloy substrate by laser deposition technique,and the microstructure characteristics were ana...Near-αtitanium alloy and Ti_(2)AlNb alloy powders premixed with different proportions were prepared on the near-αtitanium alloy substrate by laser deposition technique,and the microstructure characteristics were analyzed and discussed.Results show that numerous river-like sub-grain structures are formed inside the equiaxed B2 grains of the laser-deposited premixed titanium alloy powders with the proportion of Ti_(2)AlNb above 40wt%,whereas the needle-like structure within coarse columnarβgrains exist with the proportion of Ti_(2)AlNb below 40wt%.It is noteworthy that the decrease in laser power and scanning speed can accelerate the formation of sub-grain structures.Based on the analysis of experimental results,it can be inferred that the formation of sub-grain structure not only is related to the precipitation of O phase due to composition micro-segregation at sub-grain boundaries,but also is inseparable from the stacking faults caused by the internal stress during the laser deposition.展开更多
X-ray diffraction(XRD),scanning electron microscopy(SEM),energy-dispersive spectroscopy(EDS),electron backscatter diffraction(EBSD),and transmission electron microscopy(TEM)were used to systematically investigate the ...X-ray diffraction(XRD),scanning electron microscopy(SEM),energy-dispersive spectroscopy(EDS),electron backscatter diffraction(EBSD),and transmission electron microscopy(TEM)were used to systematically investigate the impact of rapid cold stamping on microstructural evolution and mechanical properties of spray-formed Al-Zn-Mg-Cu alloys under ambient conditions.The results reveal that the dislocation density increases with successive cold stamping passes,the volume fraction of the secondary phase(Mg(Zn,Cu,Al)_(2))increases from 15.64% to 23.94%,and the average size decreases from 1.41 to 0.75μm.The pinning effect of the secondary phases on dislocations promotes a significant transformation from low-angle grain boundaries to high-angle grain boundaries,resulting in the average grain size decreasing from 5.75 to 0.97μm.The strength and hardness of the samples increase with successive cold stamping passes,which is attributed to the synergistic effects of dislocation strengthening,grain boundary strengthening,and secondary phase strengthening.展开更多
The effects of the inter-annealing process on the microstructure,plane stress fracture toughness,and tensile properties of an AA7075 cladding sheet were investigated using optical microscopy,scanning electron microsco...The effects of the inter-annealing process on the microstructure,plane stress fracture toughness,and tensile properties of an AA7075 cladding sheet were investigated using optical microscopy,scanning electron microscopy,electron backscattered diffraction,transmission electron microscopy,and mechanical property tests.The results indicate that the plane stress fracture toughness of AA7075-T6 cladding sheet can be greatly improved.The plane stress fracture toughness for the longitudinal-transverse(L-T)and transverse-longitudinal(T-L)directions were 117.7 and 94.8 MPa·m^(1/2),respectively,after intermediate annealing at 380°C.This represents an increase of 23.9 MPa·m^(1/2)in the L-T direction and 22.6 MPa·m^(1/2) in the T-L direction compared with the AA7075-T6 cladding sheet without intermediate annealing.Moreover,the tensile strength remains similar under different conditions.Microstructure analysis indicates that intermediate annealing before heat treatment can result in long sub-grains,few recrystallized grain boundaries,and small size precipitates in AA7075-T6 cladding sheets.展开更多
基金National Natural Science Foundation of China(51974259)Xi'an Municipal Bureau of Science and Technology(21ZCZZHXJS-QCY6-0008)Industry-Academic Cooperation Project of Aero Engine Corporation of China(HFZL2020CXY021)。
文摘Near-αtitanium alloy and Ti_(2)AlNb alloy powders premixed with different proportions were prepared on the near-αtitanium alloy substrate by laser deposition technique,and the microstructure characteristics were analyzed and discussed.Results show that numerous river-like sub-grain structures are formed inside the equiaxed B2 grains of the laser-deposited premixed titanium alloy powders with the proportion of Ti_(2)AlNb above 40wt%,whereas the needle-like structure within coarse columnarβgrains exist with the proportion of Ti_(2)AlNb below 40wt%.It is noteworthy that the decrease in laser power and scanning speed can accelerate the formation of sub-grain structures.Based on the analysis of experimental results,it can be inferred that the formation of sub-grain structure not only is related to the precipitation of O phase due to composition micro-segregation at sub-grain boundaries,but also is inseparable from the stacking faults caused by the internal stress during the laser deposition.
基金supported by the National Natural Science Foundation of China(No.52271177).
文摘X-ray diffraction(XRD),scanning electron microscopy(SEM),energy-dispersive spectroscopy(EDS),electron backscatter diffraction(EBSD),and transmission electron microscopy(TEM)were used to systematically investigate the impact of rapid cold stamping on microstructural evolution and mechanical properties of spray-formed Al-Zn-Mg-Cu alloys under ambient conditions.The results reveal that the dislocation density increases with successive cold stamping passes,the volume fraction of the secondary phase(Mg(Zn,Cu,Al)_(2))increases from 15.64% to 23.94%,and the average size decreases from 1.41 to 0.75μm.The pinning effect of the secondary phases on dislocations promotes a significant transformation from low-angle grain boundaries to high-angle grain boundaries,resulting in the average grain size decreasing from 5.75 to 0.97μm.The strength and hardness of the samples increase with successive cold stamping passes,which is attributed to the synergistic effects of dislocation strengthening,grain boundary strengthening,and secondary phase strengthening.
基金the National Key R&D Program of China(Nos.2023YFB3710401,2022YFB3504401)the National Natural Science Foundation of China(Nos.52271094,U1708251)+1 种基金the Key Research and Development Program of Liaoning,China(No.2020JH2/10700003)Qingyuan City Science and Technology Plan Project(No.2023YFJH003),China.
文摘The effects of the inter-annealing process on the microstructure,plane stress fracture toughness,and tensile properties of an AA7075 cladding sheet were investigated using optical microscopy,scanning electron microscopy,electron backscattered diffraction,transmission electron microscopy,and mechanical property tests.The results indicate that the plane stress fracture toughness of AA7075-T6 cladding sheet can be greatly improved.The plane stress fracture toughness for the longitudinal-transverse(L-T)and transverse-longitudinal(T-L)directions were 117.7 and 94.8 MPa·m^(1/2),respectively,after intermediate annealing at 380°C.This represents an increase of 23.9 MPa·m^(1/2)in the L-T direction and 22.6 MPa·m^(1/2) in the T-L direction compared with the AA7075-T6 cladding sheet without intermediate annealing.Moreover,the tensile strength remains similar under different conditions.Microstructure analysis indicates that intermediate annealing before heat treatment can result in long sub-grains,few recrystallized grain boundaries,and small size precipitates in AA7075-T6 cladding sheets.
