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The cooling control of the melt during the casting process is of great significance. A comprehensive closed-loop cooling control of castings by adopting a skeletal sand mold design was proposed. The skeletal sand mold consisting of an adaptive shell, functional cavities and a support was designed and created based on the finite difference meshes of a casting. It was applied to a round wall test casting. Two kinds of skeletal sand molds, one with lattice support and the other with enforcing ribs for this casting were designed and printed out by the 3D printing (3DP) method. Aluminum alloy A356 was cast by using these two sand molds. The first mold was cooled by natural convection, the other one by water spray cooling. Two sound castings were obtained. The sand mold temperature, cooling curves, microstructures, mechanical properties, residual stress and deformation were measured, compared and discussed. Water spray cooling hastened the cooling rate by 62%, increased the content of Mg and Cu in the α-Al matrix, improved the mechanical properties, and altered the surface residual stress state.

3D printing technology has been used for sand molding and core printing, but they simply substitute the traditional molding and core making method without changing the shape or size of the sand mold (core) and their dense structure. In this study, a new type of hollow mold based on 3D printing is presented. The new type of mold is a rib reinforced thickness-varying shell mold. This mold design can realize the controlled cooling of castings, i.e., different cooling rates at different areas, and improve the temperature uniformity of a casting after its solidification. Therefore, the performance of castings can be improved and their residual stress and deformation can be reduced. This kind of new mold was applied to a stress frame of A356 aluminum alloy. The 3D printed rib reinforced thickness-varying shell mold was compared with the traditional dense mold, and the castings obtained by these two kinds of molds were also compared. The experimental results showed that the rib reinforced shell mold increased the cooling rate of the casting by 30%, tensile strength by 17%, yield strength by 11%, elongation by 67%, and decreased its deformation by 43%, while sand consumption was greatly reduced by 90%.

A rib-enforced shell mold for castings is proposed to replace the traditional dense mold. The 3D printing methods of sand mold make this new mold design a reality. The rib-enforced shell mold has been applied to cast a stress frame specimen of Al alloy A356. The effects of rib-enforced shell sand mold and traditional dense mold on the cooling of this casting have been investigated and compared. The results show that the cooling efficiency of the casting increases significantly by using rib-enforced shell mold, and approximately 40% cooling time is saved in natural condition and 35% further is saved in air blowing condition for the stress frame specimen before shakeout. This mold makes it possible to adjust the cooling condition of interested locations. It ensures fast and uniform cooling of the casting which can improve production efficiency and reduce deformation and residual stresses of the casting. Temperature distribution in the rib-enforced shell sand mold during the solidification was measured by an infrared imaging camera. The produced casting has good dimensional accuracy and surface quality. Meanwhile, nine-tenths of the sand is saved per mold.

The insulation effect of the air cavity surrounding the riser in a 3D printed sand mold was studied. The influence of the air cavity on heat flux was theoretically analyzed. The results demonstrated that the heat flux of the air cavity in the 3D printed sand mold was significantly less than that of resin-bonded sand. The insulation effect of the air cavity in sand molds for a cylinder casting and a stress-frame casting were simulated using software COMSOL. The results illustrated that the air cavity could be used to insulate the riser and it was more suitable for a lower melting point metal casting. An air cavity with 10-15 mm width and 5-10 mm away from the riser can significantly prolong the solidification of the riser by over 10%. Meanwhile, the sand mold for the stress-frame was made by 3D printing technology and poured with aluminum alloy A356 melt. The experiment results showed that the presence of the air cavity led to a 12.5% increase of the solidification time of its riser.

A shell-truss sand mold is proposed to replace the traditional dense sand mold. The shell-truss sand mold combines a sand shell with supporting and reinforcing sand truss structures, which can be fabricated by 3D printing methods It is possible to adjust the cooling conditions at specific locations of the mold. Fast and uniform cooling of a casting can be achieved, which can improve production efficiency and reduce deformation and residual stress of a casting. Several shell-truss sand mold structures were designed and used for casting a stress frame specimen. The molds were printed by the binder jetting 3D printing method and then filled with A356 Al alloy melt to make castings. The effect of the shell-truss sand mold on the cooling of the castings was investigated in comparison with the traditional dense sand mold. The cooling rate of the casting increased by using the shell-truss mold before shakeout. The casting obtained by the 3D-printed shell-truss mold had good dimensional accuracy and good surface quality. Additionally, the required amount of sand was reduced by two-thirds per mold for the shell-truss sand molds.

The author-proposed skeletal sand mold, which mainly includes a shell, air cavities and a truss support structure, has been experimentally proven to be very useful in controlling the cooling of casting at local areas and at different periods of the casting process. The modeling and simulation of the casting process using a skeletal sand mold were systemically analyzed. Complicated casting/mold and mold/air boundaries, and the thermal and mechanical behavior of the skeletal sand mold during the casting process were highlighted. A numerical simulation of the casting process of a stress frame specimen using a skeletal sand mold was performed. The temperature, stress and displacement fields of the casting and skeletal sand mold were obtained and compared with those using a traditional sand mold. The simulated results were validated with experiments. Using the skeletal sand mold, the cooling rate of the casting can be greatly improved due to the significant heat release from mold surface to environment. The residual stress and deformation of the casting can be reduced because of the decreased stiffness of this kind of mold. Although the skeletal sand mold is susceptible to cracking, it can be avoided by filleting in the conjunctions and increasing the shell thickness.

Selective laser melting SLM is one of promising additive manufacturing methods especially for precision parts Its application in copper alloys is of significance However there is rare research achievements about the effect of fabrication parameters on the microstructure and quality of copper alloy parts In this paper tin bronze CuSn bars were fabricated with different hatch distance from mm to mm and different scanning speed from mm s to mm s but same area laser energy density Porosity is mainly dependent on hatch distance instead of scanning speed The porosity decreases with the decrease of hatch distance Their microstructure was rose like fine grain cluster growing from melt pool border to pool center in which fine columnar grain is about mu m times mu m and equi axed grains is about mu m in diameter The formed specimens achieved high hardness HRB at hatch distance mm Fine microstructure leads to the improvement of mechanical properties

Titanium alloy TC owns a series of advantages such as light weight high strength weight ratio high strength at high temperatures resistance to corrosion and etc which makes it suitable for aerospace industry Selective laser melting process provides a good manufacturing method of titanium alloy parts as an alternative way to avoid the disadvantages in casting and forging The layer by layer forming way in SLM leads to unique microstructure The microstructure of SLMed TC alloy specimen was investigated The samples were treated by annealing and solutionizing aging respectively The effect on annealing temperature solution temperature and aging temperature and time on the microstructure and hardness were studied nbsp

The selective laser melting of tin bronze (CuSn10) powder was performed with a laser energy density intensity level at 210, 220, and 230 J/mm2. The composition was homogeneous with almost all tin dissolved into the matrix. The grain size of the obtained alpha copper phase was around 5 μm. The best properties were achieved at 220 J/mm2 laser energy density with a density of 8.82 g/cm3, hardness of 78.2 HRB (Rockwell Hardness measured on the B scale), yield strength of 399 MPa, tensile strength of 490 MPa, and an elongation that reached 19%. “Balling effect” appeared and resulted into a decrease of properties when the laser energy density increased to 230 J/mm2.

In this paper, we reported the laboratory spectral calibration of an ultraviolet (UV) Fourier transform imaging spectrometer (FTIS). A short overview of the designed UV-FTIS, which feature with a Cassegrain objective, an Offner relay optics system and a spatial-and-temporal modulation Michelson structure, is given. The experimental setup of spectral calibration is described, including details of the light source and integrating sphere. A high pressure mercury lamp was used to acquire reference spectrum. We calculated the all optical path difference (OPD) to achieve spectral response of every wavelength sample and divided the position of reference peak to subpixel to increase the precision of spectral calibration. The spectrum of spectral calibration show two weakly responded peaks, which was validated by reference spectrum of fiber optic spectrometer. The deviation of wavelength calibration is low to establish a best spectrometer resolution. The results of spectral calibration can meet the requirements of the UV-FTIS application.

The selective laser melting of tin bronze (CuSn10) powder was performed with a laser energy density intensity level at 210, 220, and 230 J/mm2. The composition was homogeneous with almost all tin dissolved into the matrix. The grain size of the obtained alpha copper phase was around 5 μm. The best properties were achieved at 220 J/mm2 laser energy density with a density of 8.82 g/cm3, hardness of 78.2 HRB (Rockwell Hardness measured on the B scale), yield strength of 399 MPa, tensile strength of 490 MPa, and an elongation that reached 19%. “Balling effect” appeared and resulted into a decrease of properties when the laser energy density increased to 230 J/mm2.