Textured Ti2AlC lamellar composites have been successfully fabricated by a new method in the present work.The composites exhibit high compressive strength of ca 2 GPa,fracture toughness of 8.5 MPa m1/2(//c-axis),flexu...Textured Ti2AlC lamellar composites have been successfully fabricated by a new method in the present work.The composites exhibit high compressive strength of ca 2 GPa,fracture toughness of 8.5 MPa m1/2(//c-axis),flexural strength of 735 MPa(//c-axis)and high hardness of 7.9 GPa(//c-axis).The strengthening mechanisms were discussed.The sintering and densification process was investigated and crystal orientation and microstructure were studied by electron backscattered diffraction techniques.The synthesis temperature is reduced to 1200?C by using high surface-to-volume ratio Ti2AlC nano flakes.The Lotgering orientation factor of Ti2 AlC and Ti3 AlC2{00 l}planes in the textured top surface reaches 0.74 and 0.49,respectively.This new route may shed light on resolving the difficulties encountered in large scale fabrication of textured MAX phases.展开更多
In situ ultrafine TiC dispersion reinforced Inconel 718 alloy with enhanced mechanical properties was fabricated by the technique of reactive hot-press sintering Ti2AlC and In718 powders.The effect of Ti2AlC precursor...In situ ultrafine TiC dispersion reinforced Inconel 718 alloy with enhanced mechanical properties was fabricated by the technique of reactive hot-press sintering Ti2AlC and In718 powders.The effect of Ti2AlC precursor additions(5 vol.%,10 vol.%,15 vol.%)on microstructure and mechanical properties of TiC/In718 composites were investigated.A relationship of microstructural characteristics,room and elevated temperature mechanical performance,and underlying strengthening mechanisms were analyzed.The results show that initial Ti2AlC precursor transformed completely into ultrafine TiC particulate(~230 nm)and distributed uniformly in the matrix after sintering 5 and 10 vol.%Ti2AlC/In718.However,TiC particulates tended to aggregate to stripes with the addition of Ti2AlC up to 15 vol.%,which,in adverse,weaken the properties of In718.The 5 vol.%Ti2AlC/In718 sample showed a higher tensile strength of 1404±13 MPa with a noticeable elongation of 9.8%at room temperature compared to the pure In718(ultimate tensile strength(UTS)=1310 MPa,elongation=21.5%).At 600℃,700℃,800℃and 900℃,tensile strength of the as-sintered 5 vol.%Ti2AlC/In718 composite was determined to be 1333±13 MPa,1010±10 MPa,685±25 MPa and 276±3 MPa,increased by 9.2%,14.6%,14.2%and 55%,respectively,compared with that of monolithic In718 alloy.The excellent tensile properties of TiC/In718 composite can be ascribed to the combined mechanisms in term of increased dislocation density,dispersive Orowan and load transfer mechanisms.展开更多
Highly pure and dense Ti2AlC and Ti2AlSn0.2C bulks were prepared by hot pressing with molar ratios of 1∶1.1∶0.9 and 1∶0.9∶0.2∶0.85,respectively,at 1450 ℃ for 30 min with 28 MPa in Ar atmosphere.The phase composi...Highly pure and dense Ti2AlC and Ti2AlSn0.2C bulks were prepared by hot pressing with molar ratios of 1∶1.1∶0.9 and 1∶0.9∶0.2∶0.85,respectively,at 1450 ℃ for 30 min with 28 MPa in Ar atmosphere.The phase compositions were investigated by X-ray diffraction (XRD);the surface morphology and topography of the crystal grains were also analyzed by scanning electron microscopy (SEM).The flexural strengths of Ti2AlC and Ti2AlSn0.2C have been measured as 430 and 410 MPa,respectively.Both Vickers hardness decreased slowly as the load increased.The tribological behavior was investigated by dry sliding a low-carbon steel under normal load of 20-80 N and sliding speed of 10-30 m/s.Ti2AlC bulk has a friction coefficient of 0.3-0.45 and a wear rate of (1.64-2.97)×10-6 mm3/(N·m),while Ti2AlSn0.2C bulk has a friction coefficient of 0.25-0.35 and a wear rate of (2.5-4.31)× 10-6 mm3/(N·m).The influences of Sn incorporation on the microstructure and properties of Ti2AlC have also been discussed.展开更多
基金National Natural Science Foundation of China(51731004,51671054)Fundamental Research Funds for the Central Universities in China(2242018K40108,2242018K40109)+1 种基金Natural Science Foundation of Jiangsu Province(BK20181285)Youth Research Fund Project of Anhui University of Technology。
基金financially supported by the National Key R&D Program of China(Nos.2017YFB0306201 and 2016YFB0701303).
文摘Textured Ti2AlC lamellar composites have been successfully fabricated by a new method in the present work.The composites exhibit high compressive strength of ca 2 GPa,fracture toughness of 8.5 MPa m1/2(//c-axis),flexural strength of 735 MPa(//c-axis)and high hardness of 7.9 GPa(//c-axis).The strengthening mechanisms were discussed.The sintering and densification process was investigated and crystal orientation and microstructure were studied by electron backscattered diffraction techniques.The synthesis temperature is reduced to 1200?C by using high surface-to-volume ratio Ti2AlC nano flakes.The Lotgering orientation factor of Ti2 AlC and Ti3 AlC2{00 l}planes in the textured top surface reaches 0.74 and 0.49,respectively.This new route may shed light on resolving the difficulties encountered in large scale fabrication of textured MAX phases.
基金supported financially by the National Natural Science Foundation of China(Nos.51871011,51572017 and 51301013)the Beijing Government Funds for the Constructive Project of Central Universitiesthe Fundamental Research Funds for the Central Universities(No.2018YJS144)。
文摘In situ ultrafine TiC dispersion reinforced Inconel 718 alloy with enhanced mechanical properties was fabricated by the technique of reactive hot-press sintering Ti2AlC and In718 powders.The effect of Ti2AlC precursor additions(5 vol.%,10 vol.%,15 vol.%)on microstructure and mechanical properties of TiC/In718 composites were investigated.A relationship of microstructural characteristics,room and elevated temperature mechanical performance,and underlying strengthening mechanisms were analyzed.The results show that initial Ti2AlC precursor transformed completely into ultrafine TiC particulate(~230 nm)and distributed uniformly in the matrix after sintering 5 and 10 vol.%Ti2AlC/In718.However,TiC particulates tended to aggregate to stripes with the addition of Ti2AlC up to 15 vol.%,which,in adverse,weaken the properties of In718.The 5 vol.%Ti2AlC/In718 sample showed a higher tensile strength of 1404±13 MPa with a noticeable elongation of 9.8%at room temperature compared to the pure In718(ultimate tensile strength(UTS)=1310 MPa,elongation=21.5%).At 600℃,700℃,800℃and 900℃,tensile strength of the as-sintered 5 vol.%Ti2AlC/In718 composite was determined to be 1333±13 MPa,1010±10 MPa,685±25 MPa and 276±3 MPa,increased by 9.2%,14.6%,14.2%and 55%,respectively,compared with that of monolithic In718 alloy.The excellent tensile properties of TiC/In718 composite can be ascribed to the combined mechanisms in term of increased dislocation density,dispersive Orowan and load transfer mechanisms.
基金the Fundamental Research Funds for the Central Universities，the National Natural Science Foundation of China，the Beijing Government Funds for the Constructive Project of Central Universities
文摘Highly pure and dense Ti2AlC and Ti2AlSn0.2C bulks were prepared by hot pressing with molar ratios of 1∶1.1∶0.9 and 1∶0.9∶0.2∶0.85,respectively,at 1450 ℃ for 30 min with 28 MPa in Ar atmosphere.The phase compositions were investigated by X-ray diffraction (XRD);the surface morphology and topography of the crystal grains were also analyzed by scanning electron microscopy (SEM).The flexural strengths of Ti2AlC and Ti2AlSn0.2C have been measured as 430 and 410 MPa,respectively.Both Vickers hardness decreased slowly as the load increased.The tribological behavior was investigated by dry sliding a low-carbon steel under normal load of 20-80 N and sliding speed of 10-30 m/s.Ti2AlC bulk has a friction coefficient of 0.3-0.45 and a wear rate of (1.64-2.97)×10-6 mm3/(N·m),while Ti2AlSn0.2C bulk has a friction coefficient of 0.25-0.35 and a wear rate of (2.5-4.31)× 10-6 mm3/(N·m).The influences of Sn incorporation on the microstructure and properties of Ti2AlC have also been discussed.
