It is well-known that grain refiners can tailor the microstructure and enhance the mechanical properties of titanium alloys fabricated by additive manufacturing(AM). However, the intrinsic mechanisms of Ni addition on...It is well-known that grain refiners can tailor the microstructure and enhance the mechanical properties of titanium alloys fabricated by additive manufacturing(AM). However, the intrinsic mechanisms of Ni addition on AM-built Ti–6Al–4V alloy is not well established. This limits its industrial applications. This work systematically investigated the influence of Ni additive on Ti–6Al–4V alloy fabricated by laser aided additive manufacturing(LAAM). The results showed that Ni addition yields three key effects on the microstructural evolution of LAAM-built Ti–6Al–4V alloy.(a) Ni additive remarkably refines the prior-β grains, which is due to the widened solidification range. As the Ni addition increased from 0 to 2.5 wt. %, the major-axis length and aspect ratio of the prior-β grains reduced from over 1500 μm and 7 to 97.7 μm and1.46, respectively.(b) Ni additive can discernibly induce the formation of globular α phase,which is attributed to the enhanced concentration gradient between the β and α phases. This is the driving force of globularization according to the termination mass transfer theory. The aspect ratio of the α laths decreased from 4.14 to 2.79 as the Ni addition increased from 0 to2.5 wt. %.(c) Ni as a well-known β-stabilizer and it can remarkably increase the volume fraction of β phase. Room-temperature tensile results demonstrated an increase in mechanical strength and an almost linearly decreasing elongation with increasing Ni addition. A modified mathematical model was used to quantitatively analyze the strengthening mechanism. It was evident from the results that the α lath phase and the solid solutes contribute the most to the overall yield strength of the LAAM-built Ti–6Al–4V–x Ni alloys in this work. Furthermore, the decrease in elongation with increasing Ni addition is due to the deterioration in deformability of the β phase caused by a large amount of solid-solution Ni atoms. These findings can accelerate the development of additively manufactured titanium alloys.展开更多
Parallel kinematics machine （PKM） is advantageous over the serial machine tools in processing the complex-surface products. A manufacturing service system for PKM is developed to provide the services of the complex-...Parallel kinematics machine （PKM） is advantageous over the serial machine tools in processing the complex-surface products. A manufacturing service system for PKM is developed to provide the services of the complex-surface machining for potential geographically-dispersed manufacturing enterprises. In order to easily in- tegrate the external system, Web services are used to encapsulate post-processing functions of PKM legacy sys- tems, including compilation, workspace calculation, interfere calibration, and kinematics transformation. A ser- vice-oriented architecture（SOA） is proposed for the cooperative work between the PKM system and its client. The workflow and the function module of this manufacturing service system are presented. An example shows that as a result of SOA and loose coupling, such a Web service-based manufacturing service system is easier to in- tegrate and interoperate with its client. Meanwhile, the system decreases the manufacturing cost and improves the efficiency than its former kind of distributed system.展开更多
Globularαphases can significantly improve the ductility of titanium alloys.Cyclic heat treatment(CHT)has been proved to be an effective way to induce the formation of globularαphases inα+βtitanium alloy Ti-6Al-4V ...Globularαphases can significantly improve the ductility of titanium alloys.Cyclic heat treatment(CHT)has been proved to be an effective way to induce the formation of globularαphases inα+βtitanium alloy Ti-6Al-4V fabricated by laser aided additive manufacturing(LAAM).However,there is no prior research reporting methods for obtaining globularαphases in LAAM-built near-αtitanium alloys.This work investigated the cyclic heat treatment(CHT)procedures suitable for the LAAM-built near-αtitanium alloy Ti-6Al-2Sn-4Zr-2Mo(Ti6242)to attain the globularαphases.The results show that 980℃ is the most suitable upper temperature limit for CHT.However,it is difficult to achieve a high volume fraction of the globularαphases in the LAAM-built Ti6242 alloys through CHT,which is ascribed to the low composition gradient caused by moreα-stabilizing elements and fewerβ-stabilizing elements.The as-built sample demonstrated elongation of 6.3%,which is lower than the AMS 4919J standard(elongation≥10%).After 980℃ CHT and 980℃ CHT with solution heat-treatment,the formation of the globularαphases significantly increased the elongation to 13.5%and 12.9%,respectively.Although the mechanical strength is reduced after heat-treatment,the room-temperature tensile properties still exceed the AMS 4919J standard.Fractography examination showed that the as-built sample exhibited a mixed brittle and ductile fracture behavior,while the 980℃ CHT and 980℃ CHT with solution heat-treated samples displayed ductile fracture.展开更多
The field of solid modeling has created numerous techniques for unambiguous computer representations of three-dimensional objects. Its data structures and algorithms have been used in a broad range of applications: Co...The field of solid modeling has created numerous techniques for unambiguous computer representations of three-dimensional objects. Its data structures and algorithms have been used in a broad range of applications: Computer-Aided Design and Computer-Aided Manufacturing (CAD/ CAM), robotics, computer vision, computer graphics and visualization, virtual reality, etc. This research paper is used to generate process plan from feature-based modeling, based on an integrated geometric modeling system that supports both feature-based modeling and information storage. Present system is developed only for milling components and limited to selective machining features for prismatic components and further implemented for more machining features to develop algorithms for modeling the components through the input of machining features. As a result, feature information is directly available to downstream activities, and feature extraction is no longer needed. The various systematic steps involved in this approach are study of Design, identification of Features, selection of Processes, Tools and Machines, Machining and Inspection [DFPTMMI]. Machining features generated in the design stage are recognized and stored under the Visual Basic control of CATIA software ActiveX interface. Algorithms are developed for individual features and these algorithms are embedded in Visual Basic forms. This system is discussed and suited for 2.5 Dimensional part approach, however, that can be extended to 3 dimensional prismatic part and complex features machining. Finally a process planning chart has been presented as a model process planning.展开更多
Custom-made esthetic finger prostheses, which are used for rehabilitation of patients with missing or impaired fingers, have been fabricated manually. However, such fabrication is time-consuming and requires manual sk...Custom-made esthetic finger prostheses, which are used for rehabilitation of patients with missing or impaired fingers, have been fabricated manually. However, such fabrication is time-consuming and requires manual skill. Here we propose a computer-aided method for fabricating finger pros-theses to save time and allow fabrications that do not require considerable manual skill. In this method, the dimensions of a patient’s healthy finger on the contralateral hand are first measured using a caliper. Using these dimensions, a three-dimensional model is constructed for fabricating a prosthesis for the patient’s impaired finger. Using the 3D model, a mold is designed using 3D modeling tools and a computer-aided design system. The resulting mold is then fabricated using a 3D printer. A finger prosthesis is fabricated by pouring silicone resin into the mold. A finger prosthesis for a volunteer was experimentally fabricated according to the proposed method. To evaluate the size and shape of the finger prosthesis, the difference between the finger prosthesis and the original finger of the volunteer was analyzed. Because the average difference between them was 0.25 mm, it was concluded that the proposed method could be used to fabricate a finger prosthesis of adequate size and shape.展开更多
The deepth and width of CAD application in coal mining equipments need promote furtherly. The information stream method is applied as the main clue to deal with the related technology and problems in research of manuf...The deepth and width of CAD application in coal mining equipments need promote furtherly. The information stream method is applied as the main clue to deal with the related technology and problems in research of manufacturing tools (Fixtures) planning for AFC (mining scraper bars conveyor) using CAD technique.展开更多
Laser aided additive manufacturing(LAAM)was used to fabricate bulk Fe_(49.5)Mn_(30)Co_(10)Cr_(10)C_(0.5)interstitial multicomponent alloy using pre-alloyed powder.The room temperature yield strength(σ_y),ultimate ten...Laser aided additive manufacturing(LAAM)was used to fabricate bulk Fe_(49.5)Mn_(30)Co_(10)Cr_(10)C_(0.5)interstitial multicomponent alloy using pre-alloyed powder.The room temperature yield strength(σ_y),ultimate tensile strength(σ_(UTS))and elongation(ε_(UTS))were 645 MPa,917 MPa and 27.0%respectively.The asbuilt sample consisted of equiaxed and dendritic cellular structures formed by elemental segregation.These cellular structures together with oxide particle inclusions were deemed to strengthen the material.The other contributing components include dislocation strengthening,friction stress and grain boundary strengthening.The highε_(UTS)was attributed to dislocation motion and activation of both twinning and transformation-induced plasticity(TWIP and TRIP).Tensile tests performed at-40℃and-130℃demonstrated superior tensile strength of 1041 MPa and 1267 MPa respectively.However,almost no twinning was observed in the fractured sample tested at-40℃and-130℃.Instead,higher fraction of strain-induced hexagonal close-packed(HCP)εphase transformation of 21.2%were observed for fractured sample tested at-40℃,compared with 6.3%in fractured room temperature sample.展开更多
基金supported by the Agency for Science,Technology and Research(A*Star),Republic of Singapore under the IAF-PP program‘Integrated large format hybrid manufacturing using wire-fed and powder-blown technology for LAAM process’,Grant No.A1893a0031the Academy of Sciences Project of Guangdong Province,Grant No.2016GDASRC-0105。
文摘It is well-known that grain refiners can tailor the microstructure and enhance the mechanical properties of titanium alloys fabricated by additive manufacturing(AM). However, the intrinsic mechanisms of Ni addition on AM-built Ti–6Al–4V alloy is not well established. This limits its industrial applications. This work systematically investigated the influence of Ni additive on Ti–6Al–4V alloy fabricated by laser aided additive manufacturing(LAAM). The results showed that Ni addition yields three key effects on the microstructural evolution of LAAM-built Ti–6Al–4V alloy.(a) Ni additive remarkably refines the prior-β grains, which is due to the widened solidification range. As the Ni addition increased from 0 to 2.5 wt. %, the major-axis length and aspect ratio of the prior-β grains reduced from over 1500 μm and 7 to 97.7 μm and1.46, respectively.(b) Ni additive can discernibly induce the formation of globular α phase,which is attributed to the enhanced concentration gradient between the β and α phases. This is the driving force of globularization according to the termination mass transfer theory. The aspect ratio of the α laths decreased from 4.14 to 2.79 as the Ni addition increased from 0 to2.5 wt. %.(c) Ni as a well-known β-stabilizer and it can remarkably increase the volume fraction of β phase. Room-temperature tensile results demonstrated an increase in mechanical strength and an almost linearly decreasing elongation with increasing Ni addition. A modified mathematical model was used to quantitatively analyze the strengthening mechanism. It was evident from the results that the α lath phase and the solid solutes contribute the most to the overall yield strength of the LAAM-built Ti–6Al–4V–x Ni alloys in this work. Furthermore, the decrease in elongation with increasing Ni addition is due to the deterioration in deformability of the β phase caused by a large amount of solid-solution Ni atoms. These findings can accelerate the development of additively manufactured titanium alloys.
文摘Parallel kinematics machine （PKM） is advantageous over the serial machine tools in processing the complex-surface products. A manufacturing service system for PKM is developed to provide the services of the complex-surface machining for potential geographically-dispersed manufacturing enterprises. In order to easily in- tegrate the external system, Web services are used to encapsulate post-processing functions of PKM legacy sys- tems, including compilation, workspace calculation, interfere calibration, and kinematics transformation. A ser- vice-oriented architecture（SOA） is proposed for the cooperative work between the PKM system and its client. The workflow and the function module of this manufacturing service system are presented. An example shows that as a result of SOA and loose coupling, such a Web service-based manufacturing service system is easier to in- tegrate and interoperate with its client. Meanwhile, the system decreases the manufacturing cost and improves the efficiency than its former kind of distributed system.
基金supported by Agency for Science,Technology and Research(A∗Star),the Republic of Singapore,under the IAF-PP program‘Integrated large format hybrid manufacturing using wire-fed and powder-blown technology for LAAM process’(Grant No:A1893a0031).
文摘Globularαphases can significantly improve the ductility of titanium alloys.Cyclic heat treatment(CHT)has been proved to be an effective way to induce the formation of globularαphases inα+βtitanium alloy Ti-6Al-4V fabricated by laser aided additive manufacturing(LAAM).However,there is no prior research reporting methods for obtaining globularαphases in LAAM-built near-αtitanium alloys.This work investigated the cyclic heat treatment(CHT)procedures suitable for the LAAM-built near-αtitanium alloy Ti-6Al-2Sn-4Zr-2Mo(Ti6242)to attain the globularαphases.The results show that 980℃ is the most suitable upper temperature limit for CHT.However,it is difficult to achieve a high volume fraction of the globularαphases in the LAAM-built Ti6242 alloys through CHT,which is ascribed to the low composition gradient caused by moreα-stabilizing elements and fewerβ-stabilizing elements.The as-built sample demonstrated elongation of 6.3%,which is lower than the AMS 4919J standard(elongation≥10%).After 980℃ CHT and 980℃ CHT with solution heat-treatment,the formation of the globularαphases significantly increased the elongation to 13.5%and 12.9%,respectively.Although the mechanical strength is reduced after heat-treatment,the room-temperature tensile properties still exceed the AMS 4919J standard.Fractography examination showed that the as-built sample exhibited a mixed brittle and ductile fracture behavior,while the 980℃ CHT and 980℃ CHT with solution heat-treated samples displayed ductile fracture.
文摘The field of solid modeling has created numerous techniques for unambiguous computer representations of three-dimensional objects. Its data structures and algorithms have been used in a broad range of applications: Computer-Aided Design and Computer-Aided Manufacturing (CAD/ CAM), robotics, computer vision, computer graphics and visualization, virtual reality, etc. This research paper is used to generate process plan from feature-based modeling, based on an integrated geometric modeling system that supports both feature-based modeling and information storage. Present system is developed only for milling components and limited to selective machining features for prismatic components and further implemented for more machining features to develop algorithms for modeling the components through the input of machining features. As a result, feature information is directly available to downstream activities, and feature extraction is no longer needed. The various systematic steps involved in this approach are study of Design, identification of Features, selection of Processes, Tools and Machines, Machining and Inspection [DFPTMMI]. Machining features generated in the design stage are recognized and stored under the Visual Basic control of CATIA software ActiveX interface. Algorithms are developed for individual features and these algorithms are embedded in Visual Basic forms. This system is discussed and suited for 2.5 Dimensional part approach, however, that can be extended to 3 dimensional prismatic part and complex features machining. Finally a process planning chart has been presented as a model process planning.
文摘Custom-made esthetic finger prostheses, which are used for rehabilitation of patients with missing or impaired fingers, have been fabricated manually. However, such fabrication is time-consuming and requires manual skill. Here we propose a computer-aided method for fabricating finger pros-theses to save time and allow fabrications that do not require considerable manual skill. In this method, the dimensions of a patient’s healthy finger on the contralateral hand are first measured using a caliper. Using these dimensions, a three-dimensional model is constructed for fabricating a prosthesis for the patient’s impaired finger. Using the 3D model, a mold is designed using 3D modeling tools and a computer-aided design system. The resulting mold is then fabricated using a 3D printer. A finger prosthesis is fabricated by pouring silicone resin into the mold. A finger prosthesis for a volunteer was experimentally fabricated according to the proposed method. To evaluate the size and shape of the finger prosthesis, the difference between the finger prosthesis and the original finger of the volunteer was analyzed. Because the average difference between them was 0.25 mm, it was concluded that the proposed method could be used to fabricate a finger prosthesis of adequate size and shape.
文摘The deepth and width of CAD application in coal mining equipments need promote furtherly. The information stream method is applied as the main clue to deal with the related technology and problems in research of manufacturing tools (Fixtures) planning for AFC (mining scraper bars conveyor) using CAD technique.
基金Agency for Science,Technology and Research(A*Star),Republic of Singapore,under the IAF-PP program“Integrated large format hybrid manufacturing using wire-fed and powder-blown technology for LAAM process”,Grant No:A1893a0031。
文摘Laser aided additive manufacturing(LAAM)was used to fabricate bulk Fe_(49.5)Mn_(30)Co_(10)Cr_(10)C_(0.5)interstitial multicomponent alloy using pre-alloyed powder.The room temperature yield strength(σ_y),ultimate tensile strength(σ_(UTS))and elongation(ε_(UTS))were 645 MPa,917 MPa and 27.0%respectively.The asbuilt sample consisted of equiaxed and dendritic cellular structures formed by elemental segregation.These cellular structures together with oxide particle inclusions were deemed to strengthen the material.The other contributing components include dislocation strengthening,friction stress and grain boundary strengthening.The highε_(UTS)was attributed to dislocation motion and activation of both twinning and transformation-induced plasticity(TWIP and TRIP).Tensile tests performed at-40℃and-130℃demonstrated superior tensile strength of 1041 MPa and 1267 MPa respectively.However,almost no twinning was observed in the fractured sample tested at-40℃and-130℃.Instead,higher fraction of strain-induced hexagonal close-packed(HCP)εphase transformation of 21.2%were observed for fractured sample tested at-40℃,compared with 6.3%in fractured room temperature sample.
