In order to analyze the effect of voltage during micro-arc oxidation(MAO)on corrosion and wear properties of Ti6Al4V(TC4),the MAO technology was employed to treat TC4 samples fabricated by selective electron beam melt...In order to analyze the effect of voltage during micro-arc oxidation(MAO)on corrosion and wear properties of Ti6Al4V(TC4),the MAO technology was employed to treat TC4 samples fabricated by selective electron beam melting(SEBM)at the voltages of 400,420 and 450 V.The results show that the metastable anatase phase gradually transforms to rutile phase with oxidation time and temperature increasing.The surface morphology of coating contains numerous micropores with uniform size distribution.Cracks and pores over 10μm are found on MAO-TC4 sample with applied voltage of 450 V.The thickness of MAO coating is positively correlated with the voltage.The corrosion resistance and wear resistance are related to phase composition,micropore size distribution on the surface and film thickness.When the voltage is 420 V,the coating shows the smallest corrosion current density(0.960×10^-7 A/cm^2)and the largest resistance(7.17×10^5Ω·cm^2).Under the same load condition,the coating exhibits larger friction coefficient and wear loss than the TC4 substrate.With the increase of voltage,the wear mechanism of the coating changes from abrasive wear to adhesive wear,and the adhesive wear is intensified at applied voltage of 450 V,with a maximum friction coefficient of 0.821.展开更多
A yttrium-containing high-temperature titanium alloy(Ti-6Al-2.7Sn-4Zr-0.4Mo-0.45Si-0.1Y, mass fraction, %) has been additively manufactured using selective electron beam melting(SEBM). The resulting microstructure and...A yttrium-containing high-temperature titanium alloy(Ti-6Al-2.7Sn-4Zr-0.4Mo-0.45Si-0.1Y, mass fraction, %) has been additively manufactured using selective electron beam melting(SEBM). The resulting microstructure and textures were studied using scanning electron microscopy(SEM), transmission electron microscopy(TEM), X-ray diffraction(XRD) and electron backscattered diffraction(EBSD) and compared with the conventionally manufactured form. A notable distinct difference of microstructures is that additive manufacturing by SEBM enables homogeneous precipitation of fine Y2O3 dispersoids in the size range of 50-250 nm throughout the as-fabricated alloy, despite the presence of just trace levels of oxygen(7×10-4, mass fraction) and yttrium(10-3, mass fraction) in the alloy. In contrast, the conventionally manufactured alloy shows inhomogeneously distributed coarse Y2O3 precipitates, including cracked or debonded Y2O3 particles.展开更多
In the electron beam selective melting(EBSM)process,the quality of each deposited melt track has an effect on the properties of the manufactured component.However,the formation of the melt track is governed by various...In the electron beam selective melting(EBSM)process,the quality of each deposited melt track has an effect on the properties of the manufactured component.However,the formation of the melt track is governed by various physical phenomena and influenced by various process parameters,and the correlation of these parameters is complicated and difficult to establish experimentally.The mesoscopic modeling technique was recently introduced as a means of simulating the electron beam(EB)melting process and revealing the formation mechanisms of specific melt track morphologies.However,the correlation between the process parameters and the melt track features has not yet been quantitatively understood.This paper investigates the morphological features of the melt track from the results of mesoscopic simulation,while introducing key descriptive indexes such as melt track width and height in order to numerically assess the deposition quality.The effects of various processing parameters are also quantitatively investigated,and the correlation between the processing conditions and the melt track features is thereby derived.Finally,a simulation-driven optimization framework consisting of mesoscopic modeling and data mining is proposed,and its potential and limitations are discussed.展开更多
Electron beam selective melting(EBM)and selective laser melting(SLM)are regarded as significant manufacturing processes for near-net-shaped Ti6Al4V components.Generally,in the conventional EBM process,preheating is ne...Electron beam selective melting(EBM)and selective laser melting(SLM)are regarded as significant manufacturing processes for near-net-shaped Ti6Al4V components.Generally,in the conventional EBM process,preheating is necessitated to avoid"smoke"caused by the charging of electrons.In the conventional SLM process,laser as an energy source without the risk of"smoke"can be employed to melt metal powder at low temperatures.However,because of the low absorption rate of laser,the powder bed temperature cannot reach a high level.It is difficult to obtain as-built TiAl4V with favorable comprehensive properties via conventional EBM or SLM.Hence,two types of electron beam and laser hybrid preheating(EB-LHP)combined with selective melting strategies are proposed.Using laser to preheat powder allows EBM to be performed at a low powder bed temperature(EBM-LT),whereas using an electron beam to preheat powder allows SLM to be performed at a high powder bed temperature(SLM-HT).Ti6Al4V samples are fabricated using two different manufacturing strategies(i.e.,EBM-LT and SLM-HT)and two conventional processes,i.e.,EBM at a high powder bed temperature(EBM-HT)and SLM at a low powder bed temperature(SLM-LT).The temperature-dependent surface quality,microstructure,density,and mechanical properties of the as-built Ti6Al4V samples are characterized and compared.Results show that EBM-LT Ti6Al4V exhibits a higher ultimate tensile strength(981±43 MPa)and a lower elongation(12.2%±2.3%)than EBM-HT Ti6Al4V owing to the presence ofα′martensite.The SLM-HT Ti6Al4V possesses the highest ultimate tensile strength(1,059±62 MPa)and an elongation(14.8%±4.0%)comparable to that of the EBM-HT Ti6Al4V(16.6%±1.2%).展开更多
WMoTaNbTi RHEAs formed by SEBM with negative defocus distance were investigated.Four scanning speeds were applied,an electron beam with scanning speed at 2.5 m/s completely fused the premixed WMoTaNb alloyed powder an...WMoTaNbTi RHEAs formed by SEBM with negative defocus distance were investigated.Four scanning speeds were applied,an electron beam with scanning speed at 2.5 m/s completely fused the premixed WMoTaNb alloyed powder and pure Ti powder.Significant vaporization of Nb and Ti elements happened during the formation of WMoTaNbTi RHEAs,however,the single BCC phase remains stable.Weakened solid-solute strengthening caused by elemental vaporization,dropping percentage of Nb and Ti solutes in the matrix as well as improved ductilizing effects with decreasing scanning speeds leads to falling microhardness and better local ductility.Microhardness of scanning speed at 4.0 m/s,3.5 m/s,3.0 m/s and 2.5 m/s is 578±17 HV,576±12 HV,573±10 HV and 511±2 HV,respectively.The as-deposited WMoTaNbTi RHEA formed at a scanning speed of 2.5 m/s displays ultimate strength of 1312 MPa.展开更多
The microstructure and high-temperature tensile property of a Ti-47Al-2Cr-2 Nb alloy fabricated via selective electron beam melting(SEBM) with hatch spacings of 85,100,and 115 μm were systematically investigated.When...The microstructure and high-temperature tensile property of a Ti-47Al-2Cr-2 Nb alloy fabricated via selective electron beam melting(SEBM) with hatch spacings of 85,100,and 115 μm were systematically investigated.When the hatch spacing increased from 85 to 115 μm,the microstructure comprising the horizontal cross section changed from coarse lamellar(y/B2) colonies to an inhomogeneous structure and the grain morphology transformed from elongated grains to inhomogeneous and equiaxed grains along the building direction of the vertical cross section.The boundary population of the SEBMproduced TiAl alloy samples was dominated by high-angle grain boundaries(≥ 15°),and the volume fraction of these boundaries decreased with hatch spacing increasing.Additionally,the as-built TiAl alloy sample produced under a spacing of 100 μm exhibited the highest room-and elevated-temperature tensile strengths,with the ultimate tensile strength at room temperature(642 MPa) increasing to 674 MPa at 700 ℃.Furthermore,the mechanism of anomalous strengthening at 700 ℃ was discussed in detail.展开更多
The grain morphology, nano-oxide particles and mechanical properties of oxide dispersion strengthened （ODS）-316L austenitic steel synthesized by electron beam selective melting （EBSM） technique with different post...The grain morphology, nano-oxide particles and mechanical properties of oxide dispersion strengthened （ODS）-316L austenitic steel synthesized by electron beam selective melting （EBSM） technique with different post-working processes, were explored in this study. The ODS-316L austenitic steel with superfine nano-sized oxide particles of 30-40 nm exhibits good tensile strength （412 MPa） and large total elongation （about 51%） due to the pinning effect of uniform distributed oxide particles on dislocations. After hot rolling, the specimen exhibits a higher tensile strength of 482 MPa, but the elongation decreases to 31.8% owing to the introduction of high-density dislocations. The subsequent heat treatment eliminates the grain defects induced by hot rolling and increases the randomly orientated grains, which further improves the strength and ductility of EBSM ODS-316L steel.展开更多
基金Projects(51504191,51671152,51874225)supported by the National Natural Science Foundation of ChinaProject supported by the Fund of State Key Laboratory of Porous Metal Materials,China。
文摘In order to analyze the effect of voltage during micro-arc oxidation(MAO)on corrosion and wear properties of Ti6Al4V(TC4),the MAO technology was employed to treat TC4 samples fabricated by selective electron beam melting(SEBM)at the voltages of 400,420 and 450 V.The results show that the metastable anatase phase gradually transforms to rutile phase with oxidation time and temperature increasing.The surface morphology of coating contains numerous micropores with uniform size distribution.Cracks and pores over 10μm are found on MAO-TC4 sample with applied voltage of 450 V.The thickness of MAO coating is positively correlated with the voltage.The corrosion resistance and wear resistance are related to phase composition,micropore size distribution on the surface and film thickness.When the voltage is 420 V,the coating shows the smallest corrosion current density(0.960×10^-7 A/cm^2)and the largest resistance(7.17×10^5Ω·cm^2).Under the same load condition,the coating exhibits larger friction coefficient and wear loss than the TC4 substrate.With the increase of voltage,the wear mechanism of the coating changes from abrasive wear to adhesive wear,and the adhesive wear is intensified at applied voltage of 450 V,with a maximum friction coefficient of 0.821.
基金Projects(2014KTZB01-02-03,2014KTZB01-02-04)supported by Shaanxi Science and Technology Coordination and Innovation Program,ChinaProject(DP120101672)supported by Australian Research Council(ARC)Discovery Grant,ARC Centre of Excellence for Design in Light Metals,Australia
文摘A yttrium-containing high-temperature titanium alloy(Ti-6Al-2.7Sn-4Zr-0.4Mo-0.45Si-0.1Y, mass fraction, %) has been additively manufactured using selective electron beam melting(SEBM). The resulting microstructure and textures were studied using scanning electron microscopy(SEM), transmission electron microscopy(TEM), X-ray diffraction(XRD) and electron backscattered diffraction(EBSD) and compared with the conventionally manufactured form. A notable distinct difference of microstructures is that additive manufacturing by SEBM enables homogeneous precipitation of fine Y2O3 dispersoids in the size range of 50-250 nm throughout the as-fabricated alloy, despite the presence of just trace levels of oxygen(7×10-4, mass fraction) and yttrium(10-3, mass fraction) in the alloy. In contrast, the conventionally manufactured alloy shows inhomogeneously distributed coarse Y2O3 precipitates, including cracked or debonded Y2O3 particles.
文摘In the electron beam selective melting(EBSM)process,the quality of each deposited melt track has an effect on the properties of the manufactured component.However,the formation of the melt track is governed by various physical phenomena and influenced by various process parameters,and the correlation of these parameters is complicated and difficult to establish experimentally.The mesoscopic modeling technique was recently introduced as a means of simulating the electron beam(EB)melting process and revealing the formation mechanisms of specific melt track morphologies.However,the correlation between the process parameters and the melt track features has not yet been quantitatively understood.This paper investigates the morphological features of the melt track from the results of mesoscopic simulation,while introducing key descriptive indexes such as melt track width and height in order to numerically assess the deposition quality.The effects of various processing parameters are also quantitatively investigated,and the correlation between the processing conditions and the melt track features is thereby derived.Finally,a simulation-driven optimization framework consisting of mesoscopic modeling and data mining is proposed,and its potential and limitations are discussed.
基金the National Key R&D Program(2018YFB1105200)111 Project(B17026)Open Fund of State Key Laboratory of Advanced Forming Technology and Equipment(SKL2019006)。
文摘Electron beam selective melting(EBM)and selective laser melting(SLM)are regarded as significant manufacturing processes for near-net-shaped Ti6Al4V components.Generally,in the conventional EBM process,preheating is necessitated to avoid"smoke"caused by the charging of electrons.In the conventional SLM process,laser as an energy source without the risk of"smoke"can be employed to melt metal powder at low temperatures.However,because of the low absorption rate of laser,the powder bed temperature cannot reach a high level.It is difficult to obtain as-built TiAl4V with favorable comprehensive properties via conventional EBM or SLM.Hence,two types of electron beam and laser hybrid preheating(EB-LHP)combined with selective melting strategies are proposed.Using laser to preheat powder allows EBM to be performed at a low powder bed temperature(EBM-LT),whereas using an electron beam to preheat powder allows SLM to be performed at a high powder bed temperature(SLM-HT).Ti6Al4V samples are fabricated using two different manufacturing strategies(i.e.,EBM-LT and SLM-HT)and two conventional processes,i.e.,EBM at a high powder bed temperature(EBM-HT)and SLM at a low powder bed temperature(SLM-LT).The temperature-dependent surface quality,microstructure,density,and mechanical properties of the as-built Ti6Al4V samples are characterized and compared.Results show that EBM-LT Ti6Al4V exhibits a higher ultimate tensile strength(981±43 MPa)and a lower elongation(12.2%±2.3%)than EBM-HT Ti6Al4V owing to the presence ofα′martensite.The SLM-HT Ti6Al4V possesses the highest ultimate tensile strength(1,059±62 MPa)and an elongation(14.8%±4.0%)comparable to that of the EBM-HT Ti6Al4V(16.6%±1.2%).
基金the State Key Laboratory of Porous Metal Materials,Northwest Institute for Non-ferrous Metal Research for providing the research funding。
文摘WMoTaNbTi RHEAs formed by SEBM with negative defocus distance were investigated.Four scanning speeds were applied,an electron beam with scanning speed at 2.5 m/s completely fused the premixed WMoTaNb alloyed powder and pure Ti powder.Significant vaporization of Nb and Ti elements happened during the formation of WMoTaNbTi RHEAs,however,the single BCC phase remains stable.Weakened solid-solute strengthening caused by elemental vaporization,dropping percentage of Nb and Ti solutes in the matrix as well as improved ductilizing effects with decreasing scanning speeds leads to falling microhardness and better local ductility.Microhardness of scanning speed at 4.0 m/s,3.5 m/s,3.0 m/s and 2.5 m/s is 578±17 HV,576±12 HV,573±10 HV and 511±2 HV,respectively.The as-deposited WMoTaNbTi RHEA formed at a scanning speed of 2.5 m/s displays ultimate strength of 1312 MPa.
基金financially supported by the Key Area Research and Development Program of Guangdong Province(No. 2018B090904004)the National Natural Science Foundation of China (Nos. 52001143 and 51831001)the financial support from Natural Science Research Projects in Universities of Jiangsu Province (No. 20KJB430014)。
文摘The microstructure and high-temperature tensile property of a Ti-47Al-2Cr-2 Nb alloy fabricated via selective electron beam melting(SEBM) with hatch spacings of 85,100,and 115 μm were systematically investigated.When the hatch spacing increased from 85 to 115 μm,the microstructure comprising the horizontal cross section changed from coarse lamellar(y/B2) colonies to an inhomogeneous structure and the grain morphology transformed from elongated grains to inhomogeneous and equiaxed grains along the building direction of the vertical cross section.The boundary population of the SEBMproduced TiAl alloy samples was dominated by high-angle grain boundaries(≥ 15°),and the volume fraction of these boundaries decreased with hatch spacing increasing.Additionally,the as-built TiAl alloy sample produced under a spacing of 100 μm exhibited the highest room-and elevated-temperature tensile strengths,with the ultimate tensile strength at room temperature(642 MPa) increasing to 674 MPa at 700 ℃.Furthermore,the mechanism of anomalous strengthening at 700 ℃ was discussed in detail.
基金Acknowledgements This work was subsidized by the National Natural Science Foundation of China （Grant Nos. 11175203 and 11375230）.
文摘The grain morphology, nano-oxide particles and mechanical properties of oxide dispersion strengthened （ODS）-316L austenitic steel synthesized by electron beam selective melting （EBSM） technique with different post-working processes, were explored in this study. The ODS-316L austenitic steel with superfine nano-sized oxide particles of 30-40 nm exhibits good tensile strength （412 MPa） and large total elongation （about 51%） due to the pinning effect of uniform distributed oxide particles on dislocations. After hot rolling, the specimen exhibits a higher tensile strength of 482 MPa, but the elongation decreases to 31.8% owing to the introduction of high-density dislocations. The subsequent heat treatment eliminates the grain defects induced by hot rolling and increases the randomly orientated grains, which further improves the strength and ductility of EBSM ODS-316L steel.
