Microstructure and variations in porosity in Ti-6Al-4V samples built with electron beam melting (EBM) over a range of melt scan speeds, ranging from 100 mm·s-1 to 1000 mm·s-1 were examined. Microstructure wa...Microstructure and variations in porosity in Ti-6Al-4V samples built with electron beam melting (EBM) over a range of melt scan speeds, ranging from 100 mm·s-1 to 1000 mm·s-1 were examined. Microstructure was characterized by refinement of α-phase and transformation to α′-martensite. Light optical microscopy, scanning electron microscopy, and transmission electron microscopy were used to observe these phenomena, while corresponding tensile testing and associated macro and microindentation hardness measurements were used to define the microstructural variations. Relative stiffness was observed to be linearly log-log related to relative density, corresponding to ideal porosity associated with open-cellular structures.展开更多
A novel microstructural architecture consisting of Cr23C6 carbide spatial columns was created in solid components of Co-26Cr-6Mo-0.2C fabricated from powder by additive manufacturing using electron beam melting. These...A novel microstructural architecture consisting of Cr23C6 carbide spatial columns was created in solid components of Co-26Cr-6Mo-0.2C fabricated from powder by additive manufacturing using electron beam melting. These columns of carbides extended in the build direction and are formed by the x-y rastering of the electron beam to pre-heat and melt powder layers using CAD models. These microstructural architectures are similar to rapidly solidified/unidirectionally solidified structures created by heat extraction in the direction perpendicular to the build plane. These columnar carbide architectures were observed by optical metallography and transmission electron microscopy (TEM) and compared with intrinsic stacking fault microstructures observed in annealed components. The TEM analysis allowed the details of the carbide crystal structure and corresponding cubic morphology to be observed.展开更多
文摘Microstructure and variations in porosity in Ti-6Al-4V samples built with electron beam melting (EBM) over a range of melt scan speeds, ranging from 100 mm·s-1 to 1000 mm·s-1 were examined. Microstructure was characterized by refinement of α-phase and transformation to α′-martensite. Light optical microscopy, scanning electron microscopy, and transmission electron microscopy were used to observe these phenomena, while corresponding tensile testing and associated macro and microindentation hardness measurements were used to define the microstructural variations. Relative stiffness was observed to be linearly log-log related to relative density, corresponding to ideal porosity associated with open-cellular structures.
文摘A novel microstructural architecture consisting of Cr23C6 carbide spatial columns was created in solid components of Co-26Cr-6Mo-0.2C fabricated from powder by additive manufacturing using electron beam melting. These columns of carbides extended in the build direction and are formed by the x-y rastering of the electron beam to pre-heat and melt powder layers using CAD models. These microstructural architectures are similar to rapidly solidified/unidirectionally solidified structures created by heat extraction in the direction perpendicular to the build plane. These columnar carbide architectures were observed by optical metallography and transmission electron microscopy (TEM) and compared with intrinsic stacking fault microstructures observed in annealed components. The TEM analysis allowed the details of the carbide crystal structure and corresponding cubic morphology to be observed.
