Refractory high entropy alloys have superior mechanical properties at high temperatures, and the oxidation behavior of these alloys is very important. The present work investigated the high temperature oxidation behav...Refractory high entropy alloys have superior mechanical properties at high temperatures, and the oxidation behavior of these alloys is very important. The present work investigated the high temperature oxidation behavior of three alloys with compositions of TiNbTa0.5Zr, TiNbTa0.5ZrAl and TiNbTa0.5ZrAlMo0.5, and the effects of alloying elements were discussed. Results indicated that the oxidation rates of the TiNbTa0.5Zr and TiNbTa0.5ZrAl alloys are controlled by diffusion, and obey the exponential rule. However, the oxidation rate of the TiNbTa0.5ZrAlMo0.5 alloy is controlled by interface reaction, and obeys the linear rule. The addition of Al leads to a better oxidation resistance by forming a protective oxide scale. However, the protection of Al-rich scale is weakened by the addition of Mo. Extensive pores and cracks occur in the oxide scale of the TiNbTa0.5ZrAlMo0.5 alloy, resulting in a significant decrease in oxidation resistance.展开更多
Ti−Zr alloys(oxygen content 0.42−0.54 wt.%)were prepared via powder metallurgy and hot working.The results indicate that the Ti−Zr alloys exhibit Zr-rich and Zr-lean areas with the sameα-phase structure,and the Zr-ri...Ti−Zr alloys(oxygen content 0.42−0.54 wt.%)were prepared via powder metallurgy and hot working.The results indicate that the Ti−Zr alloys exhibit Zr-rich and Zr-lean areas with the sameα-phase structure,and the Zr-rich area shows a slightly higher oxygen content and a much finer grain size.The Ti−Zr alloys present a good combination of high strength(σs=700−900 MPa)and total elongation(>20%),and solid solution strengthening of oxygen plays a major role.Zr does not influence much the oxygen-induced brittleness due to its high structural similarity to Ti.Therefore,the high value of 0.54 wt.%is still within the critical oxygen content for the ductile-to-brittle transition of Ti and does not degrade the ductility.展开更多
The effect of porosity on compressive,bending,and tensile properties of the porous tantalum scaffolds fabricated by electron beam powder bed fusion(EB-PBF)was investigated.The porous tantalum scaffolds with porosity f...The effect of porosity on compressive,bending,and tensile properties of the porous tantalum scaffolds fabricated by electron beam powder bed fusion(EB-PBF)was investigated.The porous tantalum scaffolds with porosity from 69%to 77.8%were obtained by varying the designed porosity and adjusting the processing parameters.It is found that the pores and unfused powder decrease with the increase of deposited energy density.The decrease of porosity leads to an improvement in mechanical properties.The relevancy between compressive/bending/tensile yield strength and relative density can be described appropriately by exponential model,while the relationship between elastic modulus and relative density is in good agreement with the Gibson-Ashby model.All the porous tantalum scaffolds exhibit good ductility in compressive,bending and tensile tests.No fragmentation of struts is observed during the compression process,but cracks are formed on the strut surface after 90°bending,mainly due to the high sensibility to defects caused by the oxide.展开更多
In this study,NbTaTiV refractory high-entropy alloys(RHEAs) reinforced with dispersed oxides were successfully designed and fabricated by mechanical alloying and subsequent spark plasma sintering(SPS).The effects of Y...In this study,NbTaTiV refractory high-entropy alloys(RHEAs) reinforced with dispersed oxides were successfully designed and fabricated by mechanical alloying and subsequent spark plasma sintering(SPS).The effects of Y_(2)O_(3) content on the microstructure and mechanical properties have been systematically studied.The results show that the oxide dispersion strengthening(ODS) RHEAs are mainly composed of body centered cubic(BCC) matrix and multiscale oxides,including submicron Ti-(N,O) particles,nano-sized Y-Ti-O particles and nano-sized Y_(2)O_(3) particles.The ODS-RHEAs have excellent mechanical properties due to the multisc ale oxides.With the content of Y_(2)O_(3) increasing from 1 wt% to 3 wt% Y_(2)O_(3),the compressive yield strength of the ODSRHEAs significantly increases from 1528 to 1866 MPa,while the fracture strain slightly reduces from 22% to 16%.The enhancement of the mechanical property is mainly attributed to the increased amount of multisc ale oxide particles and the refined grain structure.展开更多
基金financially supported by the National Natural Science Foundation of China(No.52171114)the Innovation-oriented Advanced Technology and Industrial Technology Program Project of Hunan Province,China(No.2020SK2017)。
基金Project(51671217)supported by the National Natural Science Foundation of ChinaProject(CX2017B047)supported by the Program of Innovation for Postgraduate of Hunan Province,China
文摘Refractory high entropy alloys have superior mechanical properties at high temperatures, and the oxidation behavior of these alloys is very important. The present work investigated the high temperature oxidation behavior of three alloys with compositions of TiNbTa0.5Zr, TiNbTa0.5ZrAl and TiNbTa0.5ZrAlMo0.5, and the effects of alloying elements were discussed. Results indicated that the oxidation rates of the TiNbTa0.5Zr and TiNbTa0.5ZrAl alloys are controlled by diffusion, and obey the exponential rule. However, the oxidation rate of the TiNbTa0.5ZrAlMo0.5 alloy is controlled by interface reaction, and obeys the linear rule. The addition of Al leads to a better oxidation resistance by forming a protective oxide scale. However, the protection of Al-rich scale is weakened by the addition of Mo. Extensive pores and cracks occur in the oxide scale of the TiNbTa0.5ZrAlMo0.5 alloy, resulting in a significant decrease in oxidation resistance.
基金Project(51625404)supported by the National Natural Science Foundation for Distinguished Young Scholar of China。
文摘Ti−Zr alloys(oxygen content 0.42−0.54 wt.%)were prepared via powder metallurgy and hot working.The results indicate that the Ti−Zr alloys exhibit Zr-rich and Zr-lean areas with the sameα-phase structure,and the Zr-rich area shows a slightly higher oxygen content and a much finer grain size.The Ti−Zr alloys present a good combination of high strength(σs=700−900 MPa)and total elongation(>20%),and solid solution strengthening of oxygen plays a major role.Zr does not influence much the oxygen-induced brittleness due to its high structural similarity to Ti.Therefore,the high value of 0.54 wt.%is still within the critical oxygen content for the ductile-to-brittle transition of Ti and does not degrade the ductility.
基金supported by the Key R&D Program of Guangdong Province,China(Nos.2019B090904001,2018B090906003)。
文摘The effect of porosity on compressive,bending,and tensile properties of the porous tantalum scaffolds fabricated by electron beam powder bed fusion(EB-PBF)was investigated.The porous tantalum scaffolds with porosity from 69%to 77.8%were obtained by varying the designed porosity and adjusting the processing parameters.It is found that the pores and unfused powder decrease with the increase of deposited energy density.The decrease of porosity leads to an improvement in mechanical properties.The relevancy between compressive/bending/tensile yield strength and relative density can be described appropriately by exponential model,while the relationship between elastic modulus and relative density is in good agreement with the Gibson-Ashby model.All the porous tantalum scaffolds exhibit good ductility in compressive,bending and tensile tests.No fragmentation of struts is observed during the compression process,but cracks are formed on the strut surface after 90°bending,mainly due to the high sensibility to defects caused by the oxide.
基金financially supported by the National Natural Science Foundation of China (Nos.51771232 and 52104365).
文摘In this study,NbTaTiV refractory high-entropy alloys(RHEAs) reinforced with dispersed oxides were successfully designed and fabricated by mechanical alloying and subsequent spark plasma sintering(SPS).The effects of Y_(2)O_(3) content on the microstructure and mechanical properties have been systematically studied.The results show that the oxide dispersion strengthening(ODS) RHEAs are mainly composed of body centered cubic(BCC) matrix and multiscale oxides,including submicron Ti-(N,O) particles,nano-sized Y-Ti-O particles and nano-sized Y_(2)O_(3) particles.The ODS-RHEAs have excellent mechanical properties due to the multisc ale oxides.With the content of Y_(2)O_(3) increasing from 1 wt% to 3 wt% Y_(2)O_(3),the compressive yield strength of the ODSRHEAs significantly increases from 1528 to 1866 MPa,while the fracture strain slightly reduces from 22% to 16%.The enhancement of the mechanical property is mainly attributed to the increased amount of multisc ale oxide particles and the refined grain structure.
