Ti_(2)AlC/TiAl composites with different volume fractions were prepared by hot pressing technology,and their reinforced structural characteristics and mechanical properties were evaluated.The results showed that when ...Ti_(2)AlC/TiAl composites with different volume fractions were prepared by hot pressing technology,and their reinforced structural characteristics and mechanical properties were evaluated.The results showed that when the reinforced phase volume fraction of Ti_(2)AlC was 20%,three-dimensional interpenetrating network structures were formed in the composites.Above 20%,Ti_(2)AlC phase in the composites accumulated and grew to form thick skeletal networks.The microplastic deformation behavior of Ti_(2)AlC phase,such as kink band and delamination,improved the fracture toughness of the composites.Comparative analysis indicated that the uniform and small interconnecting network structures could further reinforce the composites.The bending strengths of composites prepared with 20 vol.%Ti_(2)AlC reached(900.9±45.0)MPa,which was 25.5% higher than that of TiAl matrix.In general,the co-continuous Ti_(2)AlC/TiAl composite with excellent mechanical properties can be prepared by powder metallurgy method.展开更多
TiAl/Ti2AlC composites were prepared by in-situ hot pressing of TilAl/C powders mixtures and sintered at different temperatures were investigated by X- ray diffraction （ XRD ） of samples. The reaction procedure of T...TiAl/Ti2AlC composites were prepared by in-situ hot pressing of TilAl/C powders mixtures and sintered at different temperatures were investigated by X- ray diffraction （ XRD ） of samples. The reaction procedure of Ti-Al-C system could be divided into three stnges. Below 900℃ , Ti reacts with Al to form TiAl intermetallics ; above 900 ℃ , C reacts with remain Ti to form TiC triggered by the exothermal reaction of Ti and Al ; TiAl reacts with TiC to produce dense TiAl/Ti2AlC compasites.In the holding stage, ternary Ti2AlC develops to layered polycrystal and composites pyknosis in the meanwhile. The mechanism of synthesis and microstructure was especially discussed.展开更多
By using the spark plasma sintering process, Ti2AlC/TiAlcomposite with the addition of Niobium （Nb） was prepared in-situ and the microstructure of Ti2AlC/TiAl （Nb） composite was investigated by means of transmissi...By using the spark plasma sintering process, Ti2AlC/TiAlcomposite with the addition of Niobium （Nb） was prepared in-situ and the microstructure of Ti2AlC/TiAl （Nb） composite was investigated by means of transmission electron microscopy （TEM） and high-resolution electron microscopy （HREM）. The results indicate that new-formed Ti2AIC particles disperse with a high degree of uniformity and well combine with the matrix. In the area of phase interface the d-spaces of Ti2AlC （100） and TiAI （110） were measured as 0.2648 nm and 0.2991 nm,respectively. The atom arrangement beside the interface was only partly corresponding, existing in semicoherent state. On the contrary, in the area of grain interface the d-spaces of TiAl （100） and TiAl （110） were measured as 0.2462 nm and 0.2631 nm,respectively and the atom arrangement beside the interface was almost corresponding, existing in coherent state.展开更多
Improving the plasticity of TiAl alloys at room temperature has been a longstanding challenge for the de-velopment of next-generation aerospace engines.By adopting the nacre-like architecture design strategy,we have o...Improving the plasticity of TiAl alloys at room temperature has been a longstanding challenge for the de-velopment of next-generation aerospace engines.By adopting the nacre-like architecture design strategy,we have obtained a novel heterogeneous lamellar Ti_(2)AlC/TiAl composite with superior strength-plasticity synergy,i.e.,compressive strength of∼2065 MPa and fracture strain of∼27%.A combination of micropil-lar compression and large-scale atomistic simulation has revealed that the superior strength-plasticity synergy is attributed to the collaboration of Ti_(2)AlC reinforcement,lamellar architecture and heteroge-neous interface.More specifically,multiple deformation modes in Ti_(2)AlC,i.e.,basal-plane dislocations,atomic-scale ripples and kink bands,could be activated during the compression,thus promoting the plas-tic deformation capability of composite.Meanwhile,the lamellar architecture could not only induce sig-nificant stress redistribution and crack deflection between Ti_(2)AlC and TiAl,but also generate high-density SFs and DTs interactions in TiAl,leading to an improved strength and strain hardening ability.In addi-tion,profuse unique Ti_(2)AlC(1¯10¯3)/TiAl(111)interfaces in the composite could dramatically contribute to the strength and plasticity due to the interface-mediated dislocation nucleation and obstruction mecha-nisms.These findings offer a promising paradigm for tailoring microstructure of TiAl matrix composites with extraordinary strength and plasticity at ambient temperature.展开更多
In order to improve the intrinsic brittleness of TiAl alloys,Ti_(2)AlNb alloys with outstanding ductility and toughness at room temperature,and good high-temperature performance are competitive candidates in construct...In order to improve the intrinsic brittleness of TiAl alloys,Ti_(2)AlNb alloys with outstanding ductility and toughness at room temperature,and good high-temperature performance are competitive candidates in constructing the TiAl-based laminated composites.In this work,TiAl/Ti_(2)AlNb laminated composites are successfully synthesized by vacuum hot pressing combined with the foil-foil(sheet)metallurgy.Under the pressure of 65 MPa,different holding time and temperature of hot pressing are tried and the optimized fabrication parameter is acquired as 1050℃/120 min/65 MPa.Along with the changes of processing parameters,the defect,microstructure,interface,phase transformation and the corresponding mechanical properties are detailly discussed.The results show that the TiAl/Ti_(2)AlNb laminated composite fabricated at 1050℃ for 2 h achieves a good metallurgical interface bonding.The corresponding interface microstructure is composed of region I and region II.The region I consists of O,α_(2)and B2/βphase,and region II is made up ofα2.Subsequently,the tensile tests indicate that the composite synthesized at 1050℃ for 2 h possesses a maximum strength of 812 MPa and a total elongation of 1.31%at room temperature,and a strength of 539.71 MPa and the highest total elongation of 10.34%at 750℃.The well synergistic deformation ability between the interface and the two base alloys endows the composite an excellent tensile performance.Moreover,the composite processed at 1050℃ for 2 h behaves the best fracture toughness in both arrester orientation and divider orientation with the value of 32.6 MPa.m^(1/2)and 30.1 MPa.m^(1/2),respectively.The Ti_(2)AlNb alloy in the laminated structure effectively release the stress around the crack tip and plays a role in toughening.Further,crack deflection,crack bridging,crack blunting and fragmentation also make contributions to enhance the fracture toughness of the laminated composites.展开更多
The Ti_(2)AlN-reinforced TiAl(WMS)composites with different contents of Ti_(2)AlN were prepared by an in situ method of reactive arc-melting technique.According to the results of X-ray diffraction(XRD)analysis,the Ti_...The Ti_(2)AlN-reinforced TiAl(WMS)composites with different contents of Ti_(2)AlN were prepared by an in situ method of reactive arc-melting technique.According to the results of X-ray diffraction(XRD)analysis,the Ti_(2)AlNreinforced WMS composites consist ofγ-TiAl,α_(2)-Ti_(3)Al,and Ti_(2)AlN phases.Microstructure analysis results indicate that Ti_(2)AlN reinforcements with rod-like in shape form in the WMS matrix with aα_(2)/γlamellar structure containing some bulk y phases.With volume fraction of Ti_(2)AlN increasing,the grain size of the composites decreases significantly and the elasticity modulus(E)increases.The compressive strength and compressive fracture strain of the composite with 3 vol%Ti_(2)AlN have a maximum value of 1,654 MPa and 22.5%,respectively,which are approximately improved by 45.84%and 29.31%,respectively,compared with that of the unreinforced WMS alloy.展开更多
基金the financial supports from the National Natural Science Foundation of China(No.52065009)the Joint Funds of the Science and Technology Foundation of Guizhou Province,China(No.20157219)the Science and Technology Planning Project of Guizhou Province,China(No.20191069).
文摘Ti_(2)AlC/TiAl composites with different volume fractions were prepared by hot pressing technology,and their reinforced structural characteristics and mechanical properties were evaluated.The results showed that when the reinforced phase volume fraction of Ti_(2)AlC was 20%,three-dimensional interpenetrating network structures were formed in the composites.Above 20%,Ti_(2)AlC phase in the composites accumulated and grew to form thick skeletal networks.The microplastic deformation behavior of Ti_(2)AlC phase,such as kink band and delamination,improved the fracture toughness of the composites.Comparative analysis indicated that the uniform and small interconnecting network structures could further reinforce the composites.The bending strengths of composites prepared with 20 vol.%Ti_(2)AlC reached(900.9±45.0)MPa,which was 25.5% higher than that of TiAl matrix.In general,the co-continuous Ti_(2)AlC/TiAl composite with excellent mechanical properties can be prepared by powder metallurgy method.
文摘TiAl/Ti2AlC composites were prepared by in-situ hot pressing of TilAl/C powders mixtures and sintered at different temperatures were investigated by X- ray diffraction （ XRD ） of samples. The reaction procedure of Ti-Al-C system could be divided into three stnges. Below 900℃ , Ti reacts with Al to form TiAl intermetallics ; above 900 ℃ , C reacts with remain Ti to form TiC triggered by the exothermal reaction of Ti and Al ; TiAl reacts with TiC to produce dense TiAl/Ti2AlC compasites.In the holding stage, ternary Ti2AlC develops to layered polycrystal and composites pyknosis in the meanwhile. The mechanism of synthesis and microstructure was especially discussed.
基金Funded by the Shandong Provincial Natural Science Foundation (No.22003F02)
文摘By using the spark plasma sintering process, Ti2AlC/TiAlcomposite with the addition of Niobium （Nb） was prepared in-situ and the microstructure of Ti2AlC/TiAl （Nb） composite was investigated by means of transmission electron microscopy （TEM） and high-resolution electron microscopy （HREM）. The results indicate that new-formed Ti2AIC particles disperse with a high degree of uniformity and well combine with the matrix. In the area of phase interface the d-spaces of Ti2AlC （100） and TiAI （110） were measured as 0.2648 nm and 0.2991 nm,respectively. The atom arrangement beside the interface was only partly corresponding, existing in semicoherent state. On the contrary, in the area of grain interface the d-spaces of TiAl （100） and TiAl （110） were measured as 0.2462 nm and 0.2631 nm,respectively and the atom arrangement beside the interface was almost corresponding, existing in coherent state.
基金the Cultivation Project for Original Scientific Research Instruments and Equipments of Southwest Jiaotong University,China(No.XJ2021KJZK041)the Key Laboratory of Infrared Imaging Materials and Detectors,Shanghai Institute of Technical Physics,Chinese Academy of Sciences(No.IIMDKFJJ-19-08)the China Postdoctoral Science Foundation(No.2018T110993)。
基金the National Natural Science Foundation of China(Grant No.52101174)the State Key Lab of Advanced Metals and Materials(No.2022-Z15).
文摘Improving the plasticity of TiAl alloys at room temperature has been a longstanding challenge for the de-velopment of next-generation aerospace engines.By adopting the nacre-like architecture design strategy,we have obtained a novel heterogeneous lamellar Ti_(2)AlC/TiAl composite with superior strength-plasticity synergy,i.e.,compressive strength of∼2065 MPa and fracture strain of∼27%.A combination of micropil-lar compression and large-scale atomistic simulation has revealed that the superior strength-plasticity synergy is attributed to the collaboration of Ti_(2)AlC reinforcement,lamellar architecture and heteroge-neous interface.More specifically,multiple deformation modes in Ti_(2)AlC,i.e.,basal-plane dislocations,atomic-scale ripples and kink bands,could be activated during the compression,thus promoting the plas-tic deformation capability of composite.Meanwhile,the lamellar architecture could not only induce sig-nificant stress redistribution and crack deflection between Ti_(2)AlC and TiAl,but also generate high-density SFs and DTs interactions in TiAl,leading to an improved strength and strain hardening ability.In addi-tion,profuse unique Ti_(2)AlC(1¯10¯3)/TiAl(111)interfaces in the composite could dramatically contribute to the strength and plasticity due to the interface-mediated dislocation nucleation and obstruction mecha-nisms.These findings offer a promising paradigm for tailoring microstructure of TiAl matrix composites with extraordinary strength and plasticity at ambient temperature.
基金supported by Major Special Science and Technology Project of Yunnan Province 202002AB080001-3the National Natural Science Foundation of China(no.51704088)Fundamental Research and Development Program of China(Grant no.JCKY2017205B032)。
文摘In order to improve the intrinsic brittleness of TiAl alloys,Ti_(2)AlNb alloys with outstanding ductility and toughness at room temperature,and good high-temperature performance are competitive candidates in constructing the TiAl-based laminated composites.In this work,TiAl/Ti_(2)AlNb laminated composites are successfully synthesized by vacuum hot pressing combined with the foil-foil(sheet)metallurgy.Under the pressure of 65 MPa,different holding time and temperature of hot pressing are tried and the optimized fabrication parameter is acquired as 1050℃/120 min/65 MPa.Along with the changes of processing parameters,the defect,microstructure,interface,phase transformation and the corresponding mechanical properties are detailly discussed.The results show that the TiAl/Ti_(2)AlNb laminated composite fabricated at 1050℃ for 2 h achieves a good metallurgical interface bonding.The corresponding interface microstructure is composed of region I and region II.The region I consists of O,α_(2)and B2/βphase,and region II is made up ofα2.Subsequently,the tensile tests indicate that the composite synthesized at 1050℃ for 2 h possesses a maximum strength of 812 MPa and a total elongation of 1.31%at room temperature,and a strength of 539.71 MPa and the highest total elongation of 10.34%at 750℃.The well synergistic deformation ability between the interface and the two base alloys endows the composite an excellent tensile performance.Moreover,the composite processed at 1050℃ for 2 h behaves the best fracture toughness in both arrester orientation and divider orientation with the value of 32.6 MPa.m^(1/2)and 30.1 MPa.m^(1/2),respectively.The Ti_(2)AlNb alloy in the laminated structure effectively release the stress around the crack tip and plays a role in toughening.Further,crack deflection,crack bridging,crack blunting and fragmentation also make contributions to enhance the fracture toughness of the laminated composites.
基金financially supported by the National Basic Research Program of China(No.2011CB605503)the Program of Introducing Talents of Discipline to Universities(No.B08040)。
文摘The Ti_(2)AlN-reinforced TiAl(WMS)composites with different contents of Ti_(2)AlN were prepared by an in situ method of reactive arc-melting technique.According to the results of X-ray diffraction(XRD)analysis,the Ti_(2)AlNreinforced WMS composites consist ofγ-TiAl,α_(2)-Ti_(3)Al,and Ti_(2)AlN phases.Microstructure analysis results indicate that Ti_(2)AlN reinforcements with rod-like in shape form in the WMS matrix with aα_(2)/γlamellar structure containing some bulk y phases.With volume fraction of Ti_(2)AlN increasing,the grain size of the composites decreases significantly and the elasticity modulus(E)increases.The compressive strength and compressive fracture strain of the composite with 3 vol%Ti_(2)AlN have a maximum value of 1,654 MPa and 22.5%,respectively,which are approximately improved by 45.84%and 29.31%,respectively,compared with that of the unreinforced WMS alloy.
