A theoretical processing map for the laser cladding of Ti-6AI-4V powder on a Ti-6AI-4V substrate was developed. The map was constructed with the aid of a new analytical model for laser cladding, which is detailed in t...A theoretical processing map for the laser cladding of Ti-6AI-4V powder on a Ti-6AI-4V substrate was developed. The map was constructed with the aid of a new analytical model for laser cladding, which is detailed in this paper. The map is a series of loci that relate laser traversing speed with laser power for a given melt pool depth and clad height. Several of the developed parameters were experimentally trialled on Ti-6Al-4V clad on Ti-6Al-4V and produced clads of sound metallurgical quality. These maps would be useful for industrial engineers developing new cladding procedures or the research engineer developing understanding of the fundamental aspects of laser cladding. Additive manufacturing or laser engineered net shaping （LENS） could also use this type of map for the development of process parameters.展开更多
Ti-6Al-4V compacts were fabricated by metal injection molding (MIM). Influence of vacuum sintering time on mechanical properties of the sintered compacts at 1260℃were investigated. The experimental results show that ...Ti-6Al-4V compacts were fabricated by metal injection molding (MIM). Influence of vacuum sintering time on mechanical properties of the sintered compacts at 1260℃were investigated. The experimental results show that the compacts sintered at 1 260℃ for 3 hours～6 hours, which was made from hydrogenation-dehydrogenation(HDH) powder(averageparticles size is 45 μm), had a relative density of 95.6%～ 96.7%, ultimate tensile strength (648 MPa～686 MPa) and 0.2% yield strength (526 MPa～615 MPa) but a lower elongation (<4%) and that the compacts sintered at 1 260℃ for 2 hours～6 hours, which was made from 90wt% gas-atomized powder(average particles size is 32.5 μm) and 10 wt% HDH powder, had higher relative density (>95%),ultimate tensile strength (800 MPa～848 MPa), 0.2% yield strength (712 MPa～762 MPa) and high elongation (7.4%～9.5%).The mechanical properties of mixed powder specimens were nearly equivalent to the ASTM for the PM compacts.展开更多
Micro-plasma oxidation (MPO) technique is a new technique by which compound ceramic coating can be grown in situ on Al, Ti, Mg and many other valve-metals. Compound ceramic coatings on Ti-6Al-4V alloy were prepared fo...Micro-plasma oxidation (MPO) technique is a new technique by which compound ceramic coating can be grown in situ on Al, Ti, Mg and many other valve-metals. Compound ceramic coatings on Ti-6Al-4V alloy were prepared for different time by pulsed bi-polar MPO in NaAlO2 solution. The phase composition, morphology and the element distribution of the coatings were studied by XRD, SEM and JEOL SUPERPROBE 733 electric probe, respectively. Electrochemical Impedance Spectra (EIS) of the coatings were measured to study the structure character of the coatings. Through the proper EIS interpreting software, the "equivalent circuit" of the coatings was established, and the fitting values of equivalent element were calculated. The coating is mainly composed of Al2TiO5, a-A12O3 and rutile TiO2. The content of Ti element in the coating is less than that of substrate; its distribution is relatively uniform, and Ti in the outer layer is less than that in the inner layer. The content of Al in the coating is more than that of substrate, and its distribution is not even: Al in the middle part is more than that on both sides of the coating; And the EIS analysis has illustrated the double-layer structure of the coatings, and the outside layer is loosen and the inner layer compact; with the increase of the oxidizing time, the surface roughness of the coatings, and the porosity of the outer layer of the coating are increased while the compactness of the inner layer of the coatings are improved.展开更多
Compound ceramic coatings with the main crystalline of Al_2TiO_5（in the as-prepared coating without treatment） were prepared in situ on the surface Ti-6Al-4V alloy by means of pulsed bipolar micro-arc oxidation in N...Compound ceramic coatings with the main crystalline of Al_2TiO_5（in the as-prepared coating without treatment） were prepared in situ on the surface Ti-6Al-4V alloy by means of pulsed bipolar micro-arc oxidation in Na AlO_2 solution. For the purpose of studying the antioxidation properties of the samples, the coated samples treated in argon and the as-coated samples were calcined in air at 1000 °C. And the related characteristics were investigated by X-ray diffraction（XRD）, scanning electron microscopy（SEM） and X-ray fluorescence（XRF） spectroscopy, respectively. The results show that, when it was calcined in air for 1 h, Al_2TiO_5in the as-prepared coating decomposed and transformed into α-Al_2O_3 and rutile TiO_2.However, after almost 4 h in argon, Al_2TiO_5in the asprepared coating decomposed and the final coating surface contents are completely α-Al_2O_3, and those of the middle interface are mainly Al_2O_3 and Ti_2O_3. The morphologies of the coatings after calcination in argon and air are different.High-temperature oxidation occurred violently in the alloy substrate without coatings. Furthermore, the weight gain curves of the as-prepared samples and the coated samples treated in argon both show a parabolic shape.展开更多
文摘A theoretical processing map for the laser cladding of Ti-6AI-4V powder on a Ti-6AI-4V substrate was developed. The map was constructed with the aid of a new analytical model for laser cladding, which is detailed in this paper. The map is a series of loci that relate laser traversing speed with laser power for a given melt pool depth and clad height. Several of the developed parameters were experimentally trialled on Ti-6Al-4V clad on Ti-6Al-4V and produced clads of sound metallurgical quality. These maps would be useful for industrial engineers developing new cladding procedures or the research engineer developing understanding of the fundamental aspects of laser cladding. Additive manufacturing or laser engineered net shaping （LENS） could also use this type of map for the development of process parameters.
基金Supported by the Natural Science Foundation of China (50371069)the Basic Defence Research Program of China (K1802060814)+3 种基金the Doctoral Foundation of the Educational Ministry of China (20030699013)the Aviation Science Foundation (04G53044)the Opening Foundation of Jiangxi Materials Engineering Center (ZX200301014) the Doctoral Innovation Foundation of Northwestern Polytechnical University (CX200306)
文摘Ti-6Al-4V compacts were fabricated by metal injection molding (MIM). Influence of vacuum sintering time on mechanical properties of the sintered compacts at 1260℃were investigated. The experimental results show that the compacts sintered at 1 260℃ for 3 hours～6 hours, which was made from hydrogenation-dehydrogenation(HDH) powder(averageparticles size is 45 μm), had a relative density of 95.6%～ 96.7%, ultimate tensile strength (648 MPa～686 MPa) and 0.2% yield strength (526 MPa～615 MPa) but a lower elongation (<4%) and that the compacts sintered at 1 260℃ for 2 hours～6 hours, which was made from 90wt% gas-atomized powder(average particles size is 32.5 μm) and 10 wt% HDH powder, had higher relative density (>95%),ultimate tensile strength (800 MPa～848 MPa), 0.2% yield strength (712 MPa～762 MPa) and high elongation (7.4%～9.5%).The mechanical properties of mixed powder specimens were nearly equivalent to the ASTM for the PM compacts.
文摘Micro-plasma oxidation (MPO) technique is a new technique by which compound ceramic coating can be grown in situ on Al, Ti, Mg and many other valve-metals. Compound ceramic coatings on Ti-6Al-4V alloy were prepared for different time by pulsed bi-polar MPO in NaAlO2 solution. The phase composition, morphology and the element distribution of the coatings were studied by XRD, SEM and JEOL SUPERPROBE 733 electric probe, respectively. Electrochemical Impedance Spectra (EIS) of the coatings were measured to study the structure character of the coatings. Through the proper EIS interpreting software, the "equivalent circuit" of the coatings was established, and the fitting values of equivalent element were calculated. The coating is mainly composed of Al2TiO5, a-A12O3 and rutile TiO2. The content of Ti element in the coating is less than that of substrate; its distribution is relatively uniform, and Ti in the outer layer is less than that in the inner layer. The content of Al in the coating is more than that of substrate, and its distribution is not even: Al in the middle part is more than that on both sides of the coating; And the EIS analysis has illustrated the double-layer structure of the coatings, and the outside layer is loosen and the inner layer compact; with the increase of the oxidizing time, the surface roughness of the coatings, and the porosity of the outer layer of the coating are increased while the compactness of the inner layer of the coatings are improved.
基金financially supported by the Postdoctoral Science Research Developmental Foundation of Heilongjiang Province (No. LBH-Q12004)the Education Department Foundation from Heilongjiang Province (No.11521575)the Science and Technology Project of Mudanjiang, Heilongjiang Province, China (No.G2012g0008)
文摘Compound ceramic coatings with the main crystalline of Al_2TiO_5（in the as-prepared coating without treatment） were prepared in situ on the surface Ti-6Al-4V alloy by means of pulsed bipolar micro-arc oxidation in Na AlO_2 solution. For the purpose of studying the antioxidation properties of the samples, the coated samples treated in argon and the as-coated samples were calcined in air at 1000 °C. And the related characteristics were investigated by X-ray diffraction（XRD）, scanning electron microscopy（SEM） and X-ray fluorescence（XRF） spectroscopy, respectively. The results show that, when it was calcined in air for 1 h, Al_2TiO_5in the as-prepared coating decomposed and transformed into α-Al_2O_3 and rutile TiO_2.However, after almost 4 h in argon, Al_2TiO_5in the asprepared coating decomposed and the final coating surface contents are completely α-Al_2O_3, and those of the middle interface are mainly Al_2O_3 and Ti_2O_3. The morphologies of the coatings after calcination in argon and air are different.High-temperature oxidation occurred violently in the alloy substrate without coatings. Furthermore, the weight gain curves of the as-prepared samples and the coated samples treated in argon both show a parabolic shape.
