Utilizing lightweight Al alloys in various industrial applications requires achieving precise pressure tightness and leak requirements.Vacuum pressure impregnation(VPI)with thermosetting polymers is commonly used to a...Utilizing lightweight Al alloys in various industrial applications requires achieving precise pressure tightness and leak requirements.Vacuum pressure impregnation(VPI)with thermosetting polymers is commonly used to address leakage defects in die-cast Al alloys.In this study,the efficacy of the VPI technique in sealing alloy parts was investigated using a combination of nondestructive micro X-ray computed tomography(micro XCT)and a standard leak test.The results demonstrate that the commonly used water leak test is insufficient for determining the sealing performance.Instead,micro XCT shows distinct advantages by enabling more comprehensive analysis.It reveals the presence of a low atomic number impregnates sealant within casting defects,which has low grey contrast and allows for visualizing primary leakage paths in 3D.The effective atomic number of impregnated resin is 6.75 and that of Al alloy is 13.69 by dual-energy X-ray CT.This research findings will contribute to enhancing the standard VPI process parameters and the properties of impregnating sealants to improve quality assurance for impregnation in industrial metals.展开更多
The primary impregnation slurry was prepared using active alumina(56.25 mass%),kaolin(15 mass%),zirconia(3.75 mass%),deionized water(25 mass%),and extra adding FS(0.2 mass%)and CMC(0.4 mass%).The effects of the active...The primary impregnation slurry was prepared using active alumina(56.25 mass%),kaolin(15 mass%),zirconia(3.75 mass%),deionized water(25 mass%),and extra adding FS(0.2 mass%)and CMC(0.4 mass%).The effects of the active alumina particle size(d50=5.043,2.934,and 1.629μm)on the rheology and the thixotropy of the slurry were researched.It was found that the bimodal activeα-Al2O3(AMA-10)with d50=1.629μm was optimum.The secondary impregnation slurry was prepared using AMA-10,kaolin and zirconia as the main raw materials.Then the alumina-based reticulated porous ceramics were fabricated by the organic foam impregnation method combined with a secondary vacuum impregnation process.The influence of the AMA-10 content on the properties of the ceramics was studied.The residual stress of the specimens was analyzed by finite element analysis.The results show that the smaller alumina particle size and multimodal distribution are beneficial to the thixotropy of the primary impregnation slurry.The secondary vacuum impregnation technique can significantly improve the mechanical properties,the thermal shock resistance and the residual strength of the alumina-based reticulated porous ceramics.With the decrease of alumina content in the secondary impregnation slurry,the residual stress of the external layer of ceramic reinforcement gradually changes from tensile stress to compressive stress,which effectively inhibits the expansion of the surface crack,and remarkably improves the crushing strength retention ratio of alumina reticulated porous ceramics.展开更多
文摘Utilizing lightweight Al alloys in various industrial applications requires achieving precise pressure tightness and leak requirements.Vacuum pressure impregnation(VPI)with thermosetting polymers is commonly used to address leakage defects in die-cast Al alloys.In this study,the efficacy of the VPI technique in sealing alloy parts was investigated using a combination of nondestructive micro X-ray computed tomography(micro XCT)and a standard leak test.The results demonstrate that the commonly used water leak test is insufficient for determining the sealing performance.Instead,micro XCT shows distinct advantages by enabling more comprehensive analysis.It reveals the presence of a low atomic number impregnates sealant within casting defects,which has low grey contrast and allows for visualizing primary leakage paths in 3D.The effective atomic number of impregnated resin is 6.75 and that of Al alloy is 13.69 by dual-energy X-ray CT.This research findings will contribute to enhancing the standard VPI process parameters and the properties of impregnating sealants to improve quality assurance for impregnation in industrial metals.
文摘The primary impregnation slurry was prepared using active alumina(56.25 mass%),kaolin(15 mass%),zirconia(3.75 mass%),deionized water(25 mass%),and extra adding FS(0.2 mass%)and CMC(0.4 mass%).The effects of the active alumina particle size(d50=5.043,2.934,and 1.629μm)on the rheology and the thixotropy of the slurry were researched.It was found that the bimodal activeα-Al2O3(AMA-10)with d50=1.629μm was optimum.The secondary impregnation slurry was prepared using AMA-10,kaolin and zirconia as the main raw materials.Then the alumina-based reticulated porous ceramics were fabricated by the organic foam impregnation method combined with a secondary vacuum impregnation process.The influence of the AMA-10 content on the properties of the ceramics was studied.The residual stress of the specimens was analyzed by finite element analysis.The results show that the smaller alumina particle size and multimodal distribution are beneficial to the thixotropy of the primary impregnation slurry.The secondary vacuum impregnation technique can significantly improve the mechanical properties,the thermal shock resistance and the residual strength of the alumina-based reticulated porous ceramics.With the decrease of alumina content in the secondary impregnation slurry,the residual stress of the external layer of ceramic reinforcement gradually changes from tensile stress to compressive stress,which effectively inhibits the expansion of the surface crack,and remarkably improves the crushing strength retention ratio of alumina reticulated porous ceramics.
