The tensile mechanical properties and fracture behaviors of Ti 22Al 20Nb 7Ta alloys were studied at room temperature. Three typical microstructures of Ti 2AlNb based alloys were obtained by combination of thermal mech...The tensile mechanical properties and fracture behaviors of Ti 22Al 20Nb 7Ta alloys were studied at room temperature. Three typical microstructures of Ti 2AlNb based alloys were obtained by combination of thermal mechanical processing and heat treat ment. They are: 1) lath mixture of O + B 2 with remaining β grain boundaries and α 2 phase; 2) equiaxed O phase in B 2 matrix; 3) fine lath mixture of O + B 2 without remaining β grain boundaries. It is shown that the microstructure obviously affects the tensile properties of Ti 2AlNb based alloys. The microstructure of fine lath mixture of O + B 2 without remaining β grain boundaries has good combination of yield stress and ductility, while the microstructure with lath mixture of O + B 2 with remaining β grain boundaries and α 2 phase has low yield stress and elongation. The fracture mode was also controlled by the microstructure of Ti 2AlNb based alloys. By means of SEM, it was found that the dominated fracture mode of microstructure with lath mixture of O + B 2 with remained β grain boundary and α 2 phase was intergranular, and the fracture mode of the other two microstructures was mainly transgranular.展开更多
The vacuum brazing of TiAl based alloy with 40Cr steel was investigated using Ag-Cu-Ti filler metal. The experimental results show that the Ag, Cu, Ti atoms in the filler metal and the base metal inter-diffuse toward ...The vacuum brazing of TiAl based alloy with 40Cr steel was investigated using Ag-Cu-Ti filler metal. The experimental results show that the Ag, Cu, Ti atoms in the filler metal and the base metal inter-diffuse toward each other during brazing and react at the interface to form an inter-metallic AlCu 2Ti compound which joins two parts to produce a brazing joint with higher strength.展开更多
The oxidation behavior of a novel multi-element alloyed Ti2A1Nb-based alloy (Ti-22Al-25Nb-1Mo-1V-1Zr-0.2Si) was studied in the temperature range of 650-850℃. X-ray diffraction (XRD) and scanning electron microsco...The oxidation behavior of a novel multi-element alloyed Ti2A1Nb-based alloy (Ti-22Al-25Nb-1Mo-1V-1Zr-0.2Si) was studied in the temperature range of 650-850℃. X-ray diffraction (XRD) and scanning electron microscopy (SEM) equipped with an energy-dispersive spectroscopy (EDS) were used to identify the phase constituents and microstructure of the scales formed on the specimens after oxidation at different temperatures. Isothermal oxidation tests show that the oxidation rate of the alloyed TiEAlNb-based alloy is obviously reduced at all temperatures, and the mass gains are very low for this alloy in comparison with those of Ti-22Al-25Nb alloy. The alloying elements Mo, V, Zr and Si have an obvious affect on the oxidation products of the alloys. The improved oxidation resistance for the alloy is ascribed to the introduction of Mo, V, Zr and Si elements, which are beneficial to the selective oxidation of Al to form protective oxides while are disadvantage of the formation of poor oxidation resistance oxides such as AlNbO4.展开更多
The microstructure of alloy Ti 3Al 10Nb 3V 1Mo after heated at 1170℃ for 1 h and cooled to room temperature at different rates was investigated by TEM. The result showed that W.Q. microstructure consisted of sing...The microstructure of alloy Ti 3Al 10Nb 3V 1Mo after heated at 1170℃ for 1 h and cooled to room temperature at different rates was investigated by TEM. The result showed that W.Q. microstructure consisted of single B2 phase, A.C. microstructure consisted of B2 phase matrix and second phase in some regions of the B2 phase crystal grains, and C.C. and F.C. microstructure appeared as a Widmannstatten structure consisting of coarse α 2 phase plates and β phase stripes between the plates. With the decreasing of colling rate, the tension strength was obviously decreased and the plasticity was slightly increased at room temperature.展开更多
TiAlNb based intermetallic alloys,a potential competitor for next-generation super alloys,are susceptible to high-temperature embrittlement due to nucleation of a metastable single B2 phase in the fusion zone(FZ)durin...TiAlNb based intermetallic alloys,a potential competitor for next-generation super alloys,are susceptible to high-temperature embrittlement due to nucleation of a metastable single B2 phase in the fusion zone(FZ)during laser beam welding(LBW).In this study,a high entropy alloy(HEA),Ti-Hf-Zr-Cu-Ni,was self-developed and introduced as an interlayer into laser beam welded joint(LBWJ)of Ti-22 Al-27 Nb to analyze its impact on the evolution of microstructure in the weld zone(WZ)and subsequently on joint performance.Microstructural examination was carried out through electron probe micro analysis(EPMA),electron backscattered diffraction(EBSD)analysis,high-resolution scanning transmission electron microscopy(HRSTEM)comprising bright field(BF),selective area electron diffraction(SAED)and high angle annular dark-field(HAADF)imaging.Addition of the HEA into FZ of LBWJ triggered heterogenous nucleation during solidification,resultantly,fine-grained B2 with a greater proportion of high angle grain boundaries(HAGBs)was developed.FZ of Ti-22 Al-27 Nb LBWJ,prepared with an interlayer of HEA,was composed of planar,cellular,columnar and equiaxed dendritic grains;a solidification mode which was different from that observed in LBWJ prepared without adulteration of the HEA.The impact of heterogenous nucleation during epitaxial solidification on mechanical properties was established through micro vickers hardness mapping and tensile test,conducted at room temperature.The average hardness,343.5 HV,in the FZ of LBWJ prepared with an interlayer of HEA,was compatible with that of base material(BM),345 HV.The ultimate tensile strength(UTS),1062 MPa,and percentage elongation,11.2%,of the HEA tempered LBWJ were found in close approximation with that of BM,1060 MPa and 13.4%,respectively.A ductile mode of failure was observed during tensile test of the Ti-Hf-Zr-Cu-Ni supplemented LBWJ of Ti-22 Al-27 Nb,while quasi-cleavage mode of fracture was apparent in the joint of Ti-22 Al-27 Nb welded without addition of the HEA.展开更多
文摘The tensile mechanical properties and fracture behaviors of Ti 22Al 20Nb 7Ta alloys were studied at room temperature. Three typical microstructures of Ti 2AlNb based alloys were obtained by combination of thermal mechanical processing and heat treat ment. They are: 1) lath mixture of O + B 2 with remaining β grain boundaries and α 2 phase; 2) equiaxed O phase in B 2 matrix; 3) fine lath mixture of O + B 2 without remaining β grain boundaries. It is shown that the microstructure obviously affects the tensile properties of Ti 2AlNb based alloys. The microstructure of fine lath mixture of O + B 2 without remaining β grain boundaries has good combination of yield stress and ductility, while the microstructure with lath mixture of O + B 2 with remaining β grain boundaries and α 2 phase has low yield stress and elongation. The fracture mode was also controlled by the microstructure of Ti 2AlNb based alloys. By means of SEM, it was found that the dominated fracture mode of microstructure with lath mixture of O + B 2 with remained β grain boundary and α 2 phase was intergranular, and the fracture mode of the other two microstructures was mainly transgranular.
文摘The vacuum brazing of TiAl based alloy with 40Cr steel was investigated using Ag-Cu-Ti filler metal. The experimental results show that the Ag, Cu, Ti atoms in the filler metal and the base metal inter-diffuse toward each other during brazing and react at the interface to form an inter-metallic AlCu 2Ti compound which joins two parts to produce a brazing joint with higher strength.
基金financially supported by the National Natural Science Foundation of China (No. 51601146)the China Postdoctoral Science Foundation (No. 2017M613234)
文摘The oxidation behavior of a novel multi-element alloyed Ti2A1Nb-based alloy (Ti-22Al-25Nb-1Mo-1V-1Zr-0.2Si) was studied in the temperature range of 650-850℃. X-ray diffraction (XRD) and scanning electron microscopy (SEM) equipped with an energy-dispersive spectroscopy (EDS) were used to identify the phase constituents and microstructure of the scales formed on the specimens after oxidation at different temperatures. Isothermal oxidation tests show that the oxidation rate of the alloyed TiEAlNb-based alloy is obviously reduced at all temperatures, and the mass gains are very low for this alloy in comparison with those of Ti-22Al-25Nb alloy. The alloying elements Mo, V, Zr and Si have an obvious affect on the oxidation products of the alloys. The improved oxidation resistance for the alloy is ascribed to the introduction of Mo, V, Zr and Si elements, which are beneficial to the selective oxidation of Al to form protective oxides while are disadvantage of the formation of poor oxidation resistance oxides such as AlNbO4.
文摘The microstructure of alloy Ti 3Al 10Nb 3V 1Mo after heated at 1170℃ for 1 h and cooled to room temperature at different rates was investigated by TEM. The result showed that W.Q. microstructure consisted of single B2 phase, A.C. microstructure consisted of B2 phase matrix and second phase in some regions of the B2 phase crystal grains, and C.C. and F.C. microstructure appeared as a Widmannstatten structure consisting of coarse α 2 phase plates and β phase stripes between the plates. With the decreasing of colling rate, the tension strength was obviously decreased and the plasticity was slightly increased at room temperature.
基金funded by the National Natural Science Foundations of China(Nos.52075449,51975480 and U1737205)the Aeronautical Science Foundation of China(No.20185470007)。
文摘TiAlNb based intermetallic alloys,a potential competitor for next-generation super alloys,are susceptible to high-temperature embrittlement due to nucleation of a metastable single B2 phase in the fusion zone(FZ)during laser beam welding(LBW).In this study,a high entropy alloy(HEA),Ti-Hf-Zr-Cu-Ni,was self-developed and introduced as an interlayer into laser beam welded joint(LBWJ)of Ti-22 Al-27 Nb to analyze its impact on the evolution of microstructure in the weld zone(WZ)and subsequently on joint performance.Microstructural examination was carried out through electron probe micro analysis(EPMA),electron backscattered diffraction(EBSD)analysis,high-resolution scanning transmission electron microscopy(HRSTEM)comprising bright field(BF),selective area electron diffraction(SAED)and high angle annular dark-field(HAADF)imaging.Addition of the HEA into FZ of LBWJ triggered heterogenous nucleation during solidification,resultantly,fine-grained B2 with a greater proportion of high angle grain boundaries(HAGBs)was developed.FZ of Ti-22 Al-27 Nb LBWJ,prepared with an interlayer of HEA,was composed of planar,cellular,columnar and equiaxed dendritic grains;a solidification mode which was different from that observed in LBWJ prepared without adulteration of the HEA.The impact of heterogenous nucleation during epitaxial solidification on mechanical properties was established through micro vickers hardness mapping and tensile test,conducted at room temperature.The average hardness,343.5 HV,in the FZ of LBWJ prepared with an interlayer of HEA,was compatible with that of base material(BM),345 HV.The ultimate tensile strength(UTS),1062 MPa,and percentage elongation,11.2%,of the HEA tempered LBWJ were found in close approximation with that of BM,1060 MPa and 13.4%,respectively.A ductile mode of failure was observed during tensile test of the Ti-Hf-Zr-Cu-Ni supplemented LBWJ of Ti-22 Al-27 Nb,while quasi-cleavage mode of fracture was apparent in the joint of Ti-22 Al-27 Nb welded without addition of the HEA.