Major defects in forming of conical cups are wrinkles and rupture.Hydrodynamic deep drawing assisted by radial pressure（HDDRP） is a sheet hydroforming process for production of shell cups in one step.In this work,pr...Major defects in forming of conical cups are wrinkles and rupture.Hydrodynamic deep drawing assisted by radial pressure（HDDRP） is a sheet hydroforming process for production of shell cups in one step.In this work,process window diagrams（PWDs） for Al1050-O,pure copper and DIN 1623 St14 steel are obtained for HDDRP process.The PWD is determined to provide a quick assessment of part producibility for sheet hydroforming process.Finite element method is used for this purpose considering the process parameters including pressure path,and the blank material and its thickness.Numerical results are validated by experiments.It is shown that the sheets with less initial thickness and higher strength show better formability and uniformity of thickness distribution on final product.The results demonstrate that the obtained PWD can predict appropriate forming area and probability of rupture or wrinkling occurrence under different pressure loading paths.展开更多
TiAl alloys fabricated by electron beam powder bed fusion(EB-PBF)usually exhibit special microstructures with alternating fine-grained(FG)regions and coarse-grained(CG)bands.In previous studies,the CG microstructures ...TiAl alloys fabricated by electron beam powder bed fusion(EB-PBF)usually exhibit special microstructures with alternating fine-grained(FG)regions and coarse-grained(CG)bands.In previous studies,the CG microstructures were equiaxed γ phases,and the FG microstructures presented three types:near gamma,duplex,and nearly lamellar.However,the rule for controlling FG microstructures has not been found.Hence,a method needs to be built to find the rule for controlling FG microstructures.Here,we established a normalized process diagram by combining Al-equivalent and dimensionless process parameters.Based on the normalized process diagram,we successfully control the FG microstructures and customize three FG microstructures of the Ti-48Al-2Cr-2Nb alloy.Meanwhile,the average tensile yield strength reaches 756 MPa when the FG microstructure is near gamma.The yield strength is higher than the previous data for the Ti-48Al-2Cr-2Nb alloy.This is attributed to the strong interface-strengthening effect between FG near γ microstructures and CG γ bands.These findings can help shorten the research time of the other TiAl alloys fabricated by EB-PBF,improving the mechanical properties of the other EBPBF-built TiAl alloys in the future.展开更多
文摘Major defects in forming of conical cups are wrinkles and rupture.Hydrodynamic deep drawing assisted by radial pressure（HDDRP） is a sheet hydroforming process for production of shell cups in one step.In this work,process window diagrams（PWDs） for Al1050-O,pure copper and DIN 1623 St14 steel are obtained for HDDRP process.The PWD is determined to provide a quick assessment of part producibility for sheet hydroforming process.Finite element method is used for this purpose considering the process parameters including pressure path,and the blank material and its thickness.Numerical results are validated by experiments.It is shown that the sheets with less initial thickness and higher strength show better formability and uniformity of thickness distribution on final product.The results demonstrate that the obtained PWD can predict appropriate forming area and probability of rupture or wrinkling occurrence under different pressure loading paths.
基金financially supported by the National Science Foundation of China(Nos.92163215,52305379,52322101,52174364,52101143,51771093,and 12202201)the Fundamental Research Funds for the Central Universities(Nos.30922010202,and 30922010711)+4 种基金the Key Laboratory Funds for the Science and Technology of National Defense(No.6142212210103)the Natural Science Foundation of Jiangsu Province Major Project(No.BK20212009)the Xi’an Qinchuangyuan Construction of Two-Chain Integration Major Special Projects(No.23LLRHZDZX0015)the Aviation Science Foundation of AVIC(No.2024M0530S8002)the Natural Science Basic Research Program of Shaanxi Province(No.2024JC-YBQN-0579).
文摘TiAl alloys fabricated by electron beam powder bed fusion(EB-PBF)usually exhibit special microstructures with alternating fine-grained(FG)regions and coarse-grained(CG)bands.In previous studies,the CG microstructures were equiaxed γ phases,and the FG microstructures presented three types:near gamma,duplex,and nearly lamellar.However,the rule for controlling FG microstructures has not been found.Hence,a method needs to be built to find the rule for controlling FG microstructures.Here,we established a normalized process diagram by combining Al-equivalent and dimensionless process parameters.Based on the normalized process diagram,we successfully control the FG microstructures and customize three FG microstructures of the Ti-48Al-2Cr-2Nb alloy.Meanwhile,the average tensile yield strength reaches 756 MPa when the FG microstructure is near gamma.The yield strength is higher than the previous data for the Ti-48Al-2Cr-2Nb alloy.This is attributed to the strong interface-strengthening effect between FG near γ microstructures and CG γ bands.These findings can help shorten the research time of the other TiAl alloys fabricated by EB-PBF,improving the mechanical properties of the other EBPBF-built TiAl alloys in the future.
