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
Porous preforms were fabricated by cold-pressing process using powder mixture of TiC,TiO2 and dextrin.After pyrolysis and sintering,Al melt was infiltrated into the porous preforms,leading to the formation of Ti3AlC2-...Porous preforms were fabricated by cold-pressing process using powder mixture of TiC,TiO2 and dextrin.After pyrolysis and sintering,Al melt was infiltrated into the porous preforms,leading to the formation of Ti3AlC2-Al2O3-TiAl3 composite.Effects of cold-pressing pressure of preforms on microstructures and mechanical properties of the composites were studied.Synthesis mechanism and toughening mechanism of composite were also analyzed.The results shows that TiO2 is reduced into Ti2O3 by carbon,the decomposition product of dextrin,which causes the spontaneous infiltration of Al melt into TiC/Ti2O3 preform.Then, Ti3AlC2-Al2O3-TiAl3 composite is in-situ formed from the simultaneous reaction of Al melt with TiC and Ti2O3.With the increase of cold-pressing pressure from 10 MPa to 40 MPa,the pore size distribution of the preforms becomes increasingly uniform after pre-sintering,which results in the reduction of defects,and the decrease of property discrepancy of composites.Nano-laminated Ti3AlC2 grains and Al2O3 particles make the fracture toughness of TiAl3 increase remarkably by various toughening mechanisms including stress-induced microcrack,crack deflection and crack bridging.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
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).
基金Project(50802074)supported by the National Natural Science Foundation of ChinaProject(W016147)supported by the Sci-tech Innovation Foundation of Northwestern Polytechnical University,China
文摘Porous preforms were fabricated by cold-pressing process using powder mixture of TiC,TiO2 and dextrin.After pyrolysis and sintering,Al melt was infiltrated into the porous preforms,leading to the formation of Ti3AlC2-Al2O3-TiAl3 composite.Effects of cold-pressing pressure of preforms on microstructures and mechanical properties of the composites were studied.Synthesis mechanism and toughening mechanism of composite were also analyzed.The results shows that TiO2 is reduced into Ti2O3 by carbon,the decomposition product of dextrin,which causes the spontaneous infiltration of Al melt into TiC/Ti2O3 preform.Then, Ti3AlC2-Al2O3-TiAl3 composite is in-situ formed from the simultaneous reaction of Al melt with TiC and Ti2O3.With the increase of cold-pressing pressure from 10 MPa to 40 MPa,the pore size distribution of the preforms becomes increasingly uniform after pre-sintering,which results in the reduction of defects,and the decrease of property discrepancy of composites.Nano-laminated Ti3AlC2 grains and Al2O3 particles make the fracture toughness of TiAl3 increase remarkably by various toughening mechanisms including stress-induced microcrack,crack deflection and crack bridging.
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.
