A TiAl-Nb composite was prepared by spark plasma sintering （SPS） at 1250 °C and 50 MPa for 5 min from prealloyed TiAl powder and elemental Nb powder in a molar ratio of 9：1 for improving the fracture toughness...A TiAl-Nb composite was prepared by spark plasma sintering （SPS） at 1250 °C and 50 MPa for 5 min from prealloyed TiAl powder and elemental Nb powder in a molar ratio of 9：1 for improving the fracture toughness of TiAl alloy at room temperature. The microstructure, phase constitute, fracture surface and fracture toughness were determined by X-ray diffractometry, electron probe micro-analysis, scanning and transmission electron microscopy and mechanical testing. The results show that the sintered samples mainly consist of γ phase, O phase, niobium solid solution （Nbss） phase and B2 phase. The fracture toughness is as high as 28.7 MPa？m1/2 at room temperature. The ductile Nbss phase plays an important role in absorbing the fracture energy in front of the cracks. Moreover, B2 phase can branch the propagation of the cracks. The microhardness of each phase of the composite was also tested.展开更多
A fine-grained TiAl alloy with a composition of Ti-45Al-5Nb-1.5Cr-0.2W （mole fraction, %） with multiphases was prepared by spark plasma sintering （SPS） and heat-treating at 1 100 ℃ for 48 h. The relationship amon...A fine-grained TiAl alloy with a composition of Ti-45Al-5Nb-1.5Cr-0.2W （mole fraction, %） with multiphases was prepared by spark plasma sintering （SPS） and heat-treating at 1 100 ℃ for 48 h. The relationship among sintering temperature, microstructure and fracture toughness were investigated by X-ray diffractometry （XRD）, optical microscopy （OM）, scanning electron microscopy （SEM） and mechanical testing. The results show that microstructure of the bulk alloy depends on the sintering temperature strongly, and the main phase TiAl and few phases Ti3Al and niobium solid solution （Nbss） are observed in the SPS bulk samples. In the heat-treatment condition, the lamellar and Nbss phase can provide significant toughening by plastic strengthening, interface decohension, crack branch and crack bridge mechanisms. The fracture mode of the SPS TiAl composite samples is intergranular rupture and cleavage fracture.展开更多
基金Project (2011CB605505) supported by the National Basic Research Program of ChinaProject (2008AA03A233) supported by the Hi-tech Research and Development Program of China
文摘A TiAl-Nb composite was prepared by spark plasma sintering （SPS） at 1250 °C and 50 MPa for 5 min from prealloyed TiAl powder and elemental Nb powder in a molar ratio of 9：1 for improving the fracture toughness of TiAl alloy at room temperature. The microstructure, phase constitute, fracture surface and fracture toughness were determined by X-ray diffractometry, electron probe micro-analysis, scanning and transmission electron microscopy and mechanical testing. The results show that the sintered samples mainly consist of γ phase, O phase, niobium solid solution （Nbss） phase and B2 phase. The fracture toughness is as high as 28.7 MPa？m1/2 at room temperature. The ductile Nbss phase plays an important role in absorbing the fracture energy in front of the cracks. Moreover, B2 phase can branch the propagation of the cracks. The microhardness of each phase of the composite was also tested.
基金Project(2011CB605505)supported by the National Key Basic Research Program of ChinaProject(2008AA03A233)supported by the National High Technology Research and Development Program of China
文摘A fine-grained TiAl alloy with a composition of Ti-45Al-5Nb-1.5Cr-0.2W （mole fraction, %） with multiphases was prepared by spark plasma sintering （SPS） and heat-treating at 1 100 ℃ for 48 h. The relationship among sintering temperature, microstructure and fracture toughness were investigated by X-ray diffractometry （XRD）, optical microscopy （OM）, scanning electron microscopy （SEM） and mechanical testing. The results show that microstructure of the bulk alloy depends on the sintering temperature strongly, and the main phase TiAl and few phases Ti3Al and niobium solid solution （Nbss） are observed in the SPS bulk samples. In the heat-treatment condition, the lamellar and Nbss phase can provide significant toughening by plastic strengthening, interface decohension, crack branch and crack bridge mechanisms. The fracture mode of the SPS TiAl composite samples is intergranular rupture and cleavage fracture.
