To avoid high crack sensitivity of TiB-Ti composite coating during laser cladding process,network-like structure composite coating was fabricated with laser in-situ technique on titanium alloy using 5 μm TiB2 powder ...To avoid high crack sensitivity of TiB-Ti composite coating during laser cladding process,network-like structure composite coating was fabricated with laser in-situ technique on titanium alloy using 5 μm TiB2 powder as the cladding material.The microstructure,phase structure and properties of the coatings were analyzed by SEM,XRD,EPMA,TEM,hardness tester and fretting wear meter.It was observed that the outer ring of the network-like structure was mainly TiB strengthening phase,while the inner ring was α-Ti grain,and the interface between TiB and Ti matrix was very clean and had a consistent orientation relationship.The hardness of the cladding layer with network-like structure gradually decreased from the surface toward the interface,but the average hardness was nearly two times that of the substrate.In the fretting wear test,it was found that the wear resistance of the cladding layer with network-like structure was larger than that of the substrate under low load(40 N).The results revealed that the hardness and fretting wear resistance of the titanium-based composite coating could be improved by the introduction of network-like structure.展开更多
The hollow cylinders of TiB-Ti composites with a gradient distribution of Ti phase were synthesized by the combination of traditional slurry spray with centrifugal forming process.The influences of the concentration o...The hollow cylinders of TiB-Ti composites with a gradient distribution of Ti phase were synthesized by the combination of traditional slurry spray with centrifugal forming process.The influences of the concentration of sodium hexametaphosphate(SHMP),the concentration of polyvinyl alcohol(PVA)and solid content(20 vol%-35 vol%)on the rheological properties of the TiB_(2)-Ti composite slurries were investigated.Slurries with low viscosity,weak thixotropy and shear-thinning behaviour were obtained for facilitating the slurry spraying process.The effects of different centrifugal conditions on the migration of components during the forming process were studied.The phase composition and the elements distribution of the prepared samples were characterized by the energy-dispersive X-ray spectrometer.The observations revealed that the samples fabricated at 1500 r/min for 3 min had a significant composition variation.For two-phase systems with small density differences and large particle size variation,centrifugal time was more important than centrifugal speed in forming a continuous gradient structure.展开更多
A novel Ti cored wire containing Ti B2,Al60 V40 and Ti6 Al4 V mixed powders was developed for wirefeed arc deposition of Ti B/Ti composite coating,to enhance the hardness and wear resistance of Ti alloy.Results showed...A novel Ti cored wire containing Ti B2,Al60 V40 and Ti6 Al4 V mixed powders was developed for wirefeed arc deposition of Ti B/Ti composite coating,to enhance the hardness and wear resistance of Ti alloy.Results showed that after experiencing several chemical reactions,the wire was melted in the arc zone and turned into nonuniform droplets composed of Ti-Al-V-B melt and undecomposed Ti B2 particles.With the increase of welding current,the detachment time of droplet shortened while the transfer frequency accelerated,accompanied by the improvement in coating surface quality.The spatial distribution of Ti B whiskers in coating was governed by welding current.A uniform distribution could be achieved as welding current was sufficient at the expense of elevated dilution ratio,while increasing wire feeding speed could compensate the dilution loss of Ti B whisker to some extent.The decomposition process of Ti B_(2)particles and the microstructure evolution mechanism of coating was discussed in detail.The optimum coating possessed uniform microstructure,relatively low dilution ratio,and high hardness(639.1 HV_(0.5))as compared with Ti6 Al4 V substrate(326 HV_(0.5)).Indentation morphology analysis verified the excellent performance was ascribed to the load-sharing strengthening of Ti B whiskers.This study provides a high-efficiency fabrication method for the ever-developing titanium matrix composites(TMCs)coating.展开更多
In this article,in-situ scanning electron microscope characterization of the tensile properties of TiB/Ti-2Al-6Sn titanium matrix composite(TMC)was conducted before and after electroshocking treatment(EST).After EST,t...In this article,in-situ scanning electron microscope characterization of the tensile properties of TiB/Ti-2Al-6Sn titanium matrix composite(TMC)was conducted before and after electroshocking treatment(EST).After EST,the tensile strength increased by 113.2 MPa.The effect of EST on the tensile strength and fracture behavior of TiB was investigated using in-situ characterization of the fracture morphology and crack propagation path of the matrix and TiB.Before EST,TiB fracture introduced cracks that extended into the matrix,resulting in material failure.After EST,the refined TiB improved the bearing capacity of the matrix,thereby improving TMC strength.Moreover,after EST,the cracks were introduced into the matrix,and resulting the fracture of matrix first.With an increase in the external load,cracks in the matrix were observed to propagate to TiB,and the refined TiB was fractured,detached,and pulled out,resulting in the formation of pores.Analyzing the propagation path of the main crack after EST showed that the deflection angle of the main crack increased.The micro structure of the fracture surface indicated that the fracture of the matrix was plastic,whereas that of TiB was brittle.After EST,the size and area of the dimples increased,confirming the increase in plasticity.The results revealed that the comprehensive mechanical properties of TiB/Ti-2Al-6Sn improved after EST.Hence,EST is an efficient method for tailoring the micro structures and mechanical properties of TMCs.展开更多
In the present study, a series of in situ TiB/Ti6Al4V composites were fabricated using selective laser melting. The formability, microstructure evolution and mechanical properties of the as-built samples added with di...In the present study, a series of in situ TiB/Ti6Al4V composites were fabricated using selective laser melting. The formability, microstructure evolution and mechanical properties of the as-built samples added with different contents of TiB2 were studied. It is found that the densification level is related to both the content of TiB2 and laser energy density. The added TiB2 reinforcement particle can spontaneously react with titanium and then form the TiB phase. The needle-like TiB phase tends to transform into dot-like particles with the decrease in energy density. Additionally, with the increase in TiB2 content, the TiB phase is coarsened due to the increased nucleation rate and more reactions. The grain morphology is found to largely depend on the translational speed of solid–fluid interface determined by the temperature gradient and cooling rate. Also, the microhardness of the as-built TiB/Ti6Al4V composites is obviously improved. More interestingly, as the energy density increases, the microhardness of the as-built TiB/Ti6Al4V composites firstly increases and then decreases due to the synergy of grain size and different morphologies and distribution of TiB phases. The wear resistance of TiB/Ti6Al4V composites is far superior to that of Ti6Al4V alloy owing to the increased microhardness resulted from the uniform distribution of the hard TiB phase in the matrix.展开更多
TiB 2 and Ti B N films on various substrates were synthesized using ionized dc magnetron sputtering. A two turn coil powered by 13.56 MHz r.f. was used to enhance the ionization fraction of the plasma. The structure a...TiB 2 and Ti B N films on various substrates were synthesized using ionized dc magnetron sputtering. A two turn coil powered by 13.56 MHz r.f. was used to enhance the ionization fraction of the plasma. The structure and properties of the films are affected by several parameters such as substrate bias, total pressure and nitrogen partial pressure and by the substrate materials. The crystallinity and the hardness of the films increase with decreasing total pressure. Well crystallized TiB 2 films with strong (0001) texture and with hardness up to 50 GPa were produced. Nitrogen doping into TiB 2 films decreases their crystallinity and hardness. About 1 GPa residual compressive stress was determined by a wafer curvature technique. It was performed that the dry friction of several different hard films against hardened 52100 steel, which showed the TiB 2 and Ti B N films existing the lowest friction coefficient and the lowest wear rate. [展开更多
基金Projects(2019J01813,2018J01557) supported by the Natural Science Foundation of Fujian Province,ChinaProject(2018H0031) supported by the Guiding Science Program of Fujian Province,ChinaProject(2018GP2002) supported by the Science and Technology Program of Putian City,China
文摘To avoid high crack sensitivity of TiB-Ti composite coating during laser cladding process,network-like structure composite coating was fabricated with laser in-situ technique on titanium alloy using 5 μm TiB2 powder as the cladding material.The microstructure,phase structure and properties of the coatings were analyzed by SEM,XRD,EPMA,TEM,hardness tester and fretting wear meter.It was observed that the outer ring of the network-like structure was mainly TiB strengthening phase,while the inner ring was α-Ti grain,and the interface between TiB and Ti matrix was very clean and had a consistent orientation relationship.The hardness of the cladding layer with network-like structure gradually decreased from the surface toward the interface,but the average hardness was nearly two times that of the substrate.In the fretting wear test,it was found that the wear resistance of the cladding layer with network-like structure was larger than that of the substrate under low load(40 N).The results revealed that the hardness and fretting wear resistance of the titanium-based composite coating could be improved by the introduction of network-like structure.
基金National Natural Science Foundation of China(Nos.51521001,51832003,and 51911530153)。
文摘The hollow cylinders of TiB-Ti composites with a gradient distribution of Ti phase were synthesized by the combination of traditional slurry spray with centrifugal forming process.The influences of the concentration of sodium hexametaphosphate(SHMP),the concentration of polyvinyl alcohol(PVA)and solid content(20 vol%-35 vol%)on the rheological properties of the TiB_(2)-Ti composite slurries were investigated.Slurries with low viscosity,weak thixotropy and shear-thinning behaviour were obtained for facilitating the slurry spraying process.The effects of different centrifugal conditions on the migration of components during the forming process were studied.The phase composition and the elements distribution of the prepared samples were characterized by the energy-dispersive X-ray spectrometer.The observations revealed that the samples fabricated at 1500 r/min for 3 min had a significant composition variation.For two-phase systems with small density differences and large particle size variation,centrifugal time was more important than centrifugal speed in forming a continuous gradient structure.
基金financially supported by Key-Area Research and Development Program of GuangDong Province(2019B010942001)National Key R&D Program of China(No.2017YFB0703100)+1 种基金the National Natural Science Foundation of China[grant numbers 51822103,51731009 and 51671068]the Fundamental Research Funds for the Central Universities[grant number HIT.BRETIV.201902]。
文摘A novel Ti cored wire containing Ti B2,Al60 V40 and Ti6 Al4 V mixed powders was developed for wirefeed arc deposition of Ti B/Ti composite coating,to enhance the hardness and wear resistance of Ti alloy.Results showed that after experiencing several chemical reactions,the wire was melted in the arc zone and turned into nonuniform droplets composed of Ti-Al-V-B melt and undecomposed Ti B2 particles.With the increase of welding current,the detachment time of droplet shortened while the transfer frequency accelerated,accompanied by the improvement in coating surface quality.The spatial distribution of Ti B whiskers in coating was governed by welding current.A uniform distribution could be achieved as welding current was sufficient at the expense of elevated dilution ratio,while increasing wire feeding speed could compensate the dilution loss of Ti B whisker to some extent.The decomposition process of Ti B_(2)particles and the microstructure evolution mechanism of coating was discussed in detail.The optimum coating possessed uniform microstructure,relatively low dilution ratio,and high hardness(639.1 HV_(0.5))as compared with Ti6 Al4 V substrate(326 HV_(0.5)).Indentation morphology analysis verified the excellent performance was ascribed to the load-sharing strengthening of Ti B whiskers.This study provides a high-efficiency fabrication method for the ever-developing titanium matrix composites(TMCs)coating.
基金financially supported by the National Natural Science Foundation of China(No.52271135)the Major Research Plan of the National Natural Science Foundation of China(No.92266102)+5 种基金the Natural Science Foundation of Hubei Province(No.2022CFB492)the Knowledge Innovation Program of Wuhan-Basic Research(No.2022010801010174)the Application Foundation Frontier Project of Wuhan(No.2020010601012171)"Chu Tian Scholar"Project of Hubei Province(No.CTXZ2017-05)the Overseas Expertise Introduction Project for Discipline Innovation(No.B17034)the Innovative Research Team Development Program of Ministry of Education of China(No.IRT_17R83)。
文摘In this article,in-situ scanning electron microscope characterization of the tensile properties of TiB/Ti-2Al-6Sn titanium matrix composite(TMC)was conducted before and after electroshocking treatment(EST).After EST,the tensile strength increased by 113.2 MPa.The effect of EST on the tensile strength and fracture behavior of TiB was investigated using in-situ characterization of the fracture morphology and crack propagation path of the matrix and TiB.Before EST,TiB fracture introduced cracks that extended into the matrix,resulting in material failure.After EST,the refined TiB improved the bearing capacity of the matrix,thereby improving TMC strength.Moreover,after EST,the cracks were introduced into the matrix,and resulting the fracture of matrix first.With an increase in the external load,cracks in the matrix were observed to propagate to TiB,and the refined TiB was fractured,detached,and pulled out,resulting in the formation of pores.Analyzing the propagation path of the main crack after EST showed that the deflection angle of the main crack increased.The micro structure of the fracture surface indicated that the fracture of the matrix was plastic,whereas that of TiB was brittle.After EST,the size and area of the dimples increased,confirming the increase in plasticity.The results revealed that the comprehensive mechanical properties of TiB/Ti-2Al-6Sn improved after EST.Hence,EST is an efficient method for tailoring the micro structures and mechanical properties of TMCs.
基金the Civil Aerospace Pre-research Project:research on additive manufacturing of core components in the liquid rocket enginethe Fundamental Research Funds for the Central Universities(Nos.2019kfyXMPY005 and 2019kfyXKJC042)。
文摘In the present study, a series of in situ TiB/Ti6Al4V composites were fabricated using selective laser melting. The formability, microstructure evolution and mechanical properties of the as-built samples added with different contents of TiB2 were studied. It is found that the densification level is related to both the content of TiB2 and laser energy density. The added TiB2 reinforcement particle can spontaneously react with titanium and then form the TiB phase. The needle-like TiB phase tends to transform into dot-like particles with the decrease in energy density. Additionally, with the increase in TiB2 content, the TiB phase is coarsened due to the increased nucleation rate and more reactions. The grain morphology is found to largely depend on the translational speed of solid–fluid interface determined by the temperature gradient and cooling rate. Also, the microhardness of the as-built TiB/Ti6Al4V composites is obviously improved. More interestingly, as the energy density increases, the microhardness of the as-built TiB/Ti6Al4V composites firstly increases and then decreases due to the synergy of grain size and different morphologies and distribution of TiB phases. The wear resistance of TiB/Ti6Al4V composites is far superior to that of Ti6Al4V alloy owing to the increased microhardness resulted from the uniform distribution of the hard TiB phase in the matrix.
文摘TiB 2 and Ti B N films on various substrates were synthesized using ionized dc magnetron sputtering. A two turn coil powered by 13.56 MHz r.f. was used to enhance the ionization fraction of the plasma. The structure and properties of the films are affected by several parameters such as substrate bias, total pressure and nitrogen partial pressure and by the substrate materials. The crystallinity and the hardness of the films increase with decreasing total pressure. Well crystallized TiB 2 films with strong (0001) texture and with hardness up to 50 GPa were produced. Nitrogen doping into TiB 2 films decreases their crystallinity and hardness. About 1 GPa residual compressive stress was determined by a wafer curvature technique. It was performed that the dry friction of several different hard films against hardened 52100 steel, which showed the TiB 2 and Ti B N films existing the lowest friction coefficient and the lowest wear rate. [
