Investment casting shell moulds are widely applied to cast alloys, but how to efficiently form a hierarchical porous structure inside the wall is an innovation and challenge. In this research, porous shell moulds with...Investment casting shell moulds are widely applied to cast alloys, but how to efficiently form a hierarchical porous structure inside the wall is an innovation and challenge. In this research, porous shell moulds with three infill patterns(rectilinear, grid, and honeycomb) were prepared using bauxite slurry and slurry extrusionbased additive manufacturing technology, and the effects of infill patterns on the properties were evaluated. The hierarchical pores inside the wall are composed of the macropores formed by infills and the micropores among bauxite particles. Different infill patterns result in changes in distribution and shape of pores, thereby affecting the properties of the shell moulds. The honeycomb pattern has more comprehensive advantages compared to the other two infill patterns. The samples prepared with the honeycomb pattern exhibit the highest bending strength(11.62 MPa) and porosity(41.6%), as well as good heat-transfer ability, with an average shrinkage rate within 2.0%. This work provides an attractive feasibility for fabricating shell moulds with hierarchical porous walls.展开更多
Phosphate-bonded investments have already been widely utilized in dental restoration and micro-casting of artistic products for its outstanding rapid setting and high strength. However, the rapid setting rate of inves...Phosphate-bonded investments have already been widely utilized in dental restoration and micro-casting of artistic products for its outstanding rapid setting and high strength. However, the rapid setting rate of investment slurry has up to now been a barrier to extend the use of such slurry in preparation of medium-sized ceramic moulds. This paper proposes a new process of rapid fabrication of magnesia-phosphate-bonded investment ceramic moulds for medium-sized superalloy castings utilizing bauxite and mullite as refractory aggregates. In order to determine the properties of magnesia-phosphate-bonded bauxite-mullite investments (MPBBMI), a series of experiments were conducted, including modifciation of the workable time of slurry by liquid(mL)/powder(g)(L/P) ratio and addition of boric acid as retard agent and sodium tri-polyphosphate (STP) as strengthening agent, and adjustment of bauxite (g)/mullite(g)(B/M) ratio for mechanical strength. Mechanical vibration was applied to improve initial setting time and fluidity when pouring investment slurry; then an intermediate size ceramic mould for superalloy castings was manufactured by means of this rapid preparing process with MPBBMI material. The results showed that the MPBBMI slurry exhibits proper initial setting time and excellent fluidity when the L/P ratio is 0.64 and the boric acid content is 0.88wt.%. The fired specimens made from the MPBBMI material demonstrated adequate compression strength to withstand impact force of molten metal when the B/M ratio is 0.89 and the STP content is 0.92wt.%. The experimental results confirmed the feasibility of the proposed rapid fabricating process for medium-sized ceramic moulds with MPBBMI material by appropriate measures.展开更多
This study proposes an innovative precast shear wall system, called an EVE precast hollow shear wall structure (EVE-PHSW). Precast panels in EVE-PHSW are simultaneously precast with vertical and horizontal holes. Nonc...This study proposes an innovative precast shear wall system, called an EVE precast hollow shear wall structure (EVE-PHSW). Precast panels in EVE-PHSW are simultaneously precast with vertical and horizontal holes. Noncontact lap splices of rebars are used in vertical joints connecting adjacent precast panels for automated prefabrication and easy in situ erection. The seismic behavior of EVE walls was examined through a series of tests on six wall specimens with aspect ratios of 1.0~1.3. Test results showed that EVE wall specimens with inside cast-in situ concrete achieved the desired “strong bending and weak shear” and failed in shear mode. Common main diagonal cracks and brittle shear failure in squat cast-in situ walls were prevented. Inside cast-in situ concrete could signifi cantly improve the shear strength and stiff ness of EVE walls. The details of boundary elements (cast-in situ or prefabricated) and vertical joints (contiguous or spaced) had little eff ect on the global behavior of EVE walls. Noncontact lap splices in vertical joints could enable EVE walls to exhibit stable load-carrying capacity through extensive deformations. Evaluation on design codes revealed that both JGJ 3-2010 and ACI 318-14 provide conservative estimation of shear strength of EVE walls, and EVE walls achieved shear strength reserves comparative to cast-in situ walls. The recommended eff ective stiff ness for cast-in situ walls in ASCE 41-17 appeared to be appropriate for EVE walls.展开更多
Unsteady fluid flows and level fluctuations in a thin slab continuous casting mould have significant influence on product quality. In this study, the phenomena concerning transient flow features and free surface motio...Unsteady fluid flows and level fluctuations in a thin slab continuous casting mould have significant influence on product quality. In this study, the phenomena concerning transient flow features and free surface motions were analyzed by means of the large eddy simulation （LES） software with the smagorinsky SGS model--VisualCast （VCast） II, where the Simpler algorithm on a body-fitted mesh was used to resolve governing equations. A series of water analog experiments on the fluid flow and the surface wave in the moulds of thin slab continuous casting were also performed. The results of fluid regions, middle of vortex and level fluctuation from digital simulations were identical with the results of the water analog experiments.展开更多
In an injection moulding process, the mould cooling s ystem is very important as an efficient and uniform cooling effect can improve b oth the productivity and part quality. Due to the complexity of the process, muc h...In an injection moulding process, the mould cooling s ystem is very important as an efficient and uniform cooling effect can improve b oth the productivity and part quality. Due to the complexity of the process, muc h research on the mould cooling analysis and cooling design optimization has bee n focused on the core and the cavity, excluding other systems of injection mould s. However, the runner system introduces a considerable amount of heat into the mould. In recent years, more and more hot runner systems are being applied in th e moulding industry to save material and decrease losses of injection pressure. This raises the need to include the hot runner system in the cooling analysis. I n this paper, a photo frame part was studied. The mould was built with a hot run ner system. Two thermal sensors were installed: one measures the temperature of lateral surface of hot runner nozzle; the other measures the plastic temperature from the core side. A pressure sensor was also installed to measure the pressur e of the core impression. Cooling analysis was performed using ABAQUS, ananalysi s software based on the Finite Element Method (FEM). The assembly including core , cavity and plastic part was modeled. Heat conduction from hot runner to cavity and from polymer melt to the mould and force convection on the cooling channel surfaces were studied. The natural convection between the ambient air and the ex terior mould surface was ignored. The simulations were adjusted with the experim ental results to find out the heat input from hot runner and its influence on mo uld cooling. Finally, the optimal cooling design and optimal injection condition were obtained.展开更多
The characteristic of metallographic structure of the SnSb alloy moulds is that hard particles are distributed on the soft metal matrix. Great difference of the hard particles and the soft metal matrix’hardness makes...The characteristic of metallographic structure of the SnSb alloy moulds is that hard particles are distributed on the soft metal matrix. Great difference of the hard particles and the soft metal matrix’hardness makes moulds’polishing become difficult. When a rigid grindstone is used to polish the surface of the SnSb alloy mould, the hard abrasives fall off and are embed in the soft matrix of SnSb alloy and while the process, the grinding chips are able to block the gap on the grindstone surface and enable the grindstone to blunt, which brings about the polished area on the surface of the mould is seriously squeezed and deformed and the crystal lattice of SnSb alloys is seriously distorted, and the work hardening takes place. At the same time, the rigid grindstone is easy to scratch the surface of the SnSb alloy mould. Owing to the above reasons, it is difficult to reduce surface roughness and improve the surface quality of SnSb alloy moulds. Taking use of the CAD/CAM technique and the complex processing of combining electrolyzing polishing and mechanical polishing with the magnetic force, mould’s polishing automation is realized on the numerical control machine tool. This complex processing is finished under a comprehensive action as the following: 1. Electrolyzing polishing action Under the electric field, the electrolyte between the elastic grind wheel and the mould is ionized, which electrolyzes the metal of the mould’s surface. The electrolyzing speed of convex peak on the mould’s surface is faster than that of concave valley, which levels the mould’s surface. 2. Mechanical Polishing action During electrolyzing, a dense passive film of low hardness is formed on the mould’s surface. While polishing, soft grinding wheel scraps the passive film on the conven peak easily, and the new metal surface is exposed, then, a new passive film is formed again, going round and round, the conven peak on the mould’s surface is leveled quickly. 3. Magnetic force action The charged particles in electric field will be acted by the Lorentz force in magnetic field. The field plays a stirring part on electrolyte and reduces electrochemical polarization and concentration polarization, and accelerates the electrochemical reaction. The complex polishing process is not only of high efficiency, but also of good surface quality and provides a good effective method for the non-ferrous metal polishing. When the mould is polished, a speed-raising tool system is used and it can increase the grinding wheel spindle’s speed up to five times. This paper describes the SnSb alloy moulds’polishing steps, grinding wheel speed-raising tool system, polishing principle and the results.展开更多
Today, the time-to-market for plastic products ar e getting shorter, thus the lead-time for making the injection mould is decreasin g. There is potential in timesavings in the mould design stage because the design pro...Today, the time-to-market for plastic products ar e getting shorter, thus the lead-time for making the injection mould is decreasin g. There is potential in timesavings in the mould design stage because the design process that is repeatable for every mould design can be standardized. T he preliminary work of any final plastic injection mould design is to always pro vide an initial design of the mould assembly for product designers (customers) p rior to receiving the final product CAD data. Traditionally and even up till no w, this initial design is always created using 2D CAD packages. The information used for the initial design is based on the technical discussion checklist, in which most mould makers have their own standards. This checklist is also being used as a quotation since the most basic information of the mould in the particu lar project is being recorded in it. The basic information in this checklist in cludes the number of cavities, the type of mould base to be used, the moulding m achine to be used for the moulding, the type of gating system, the type of resin material used and its shrinkage value etc. Information on special requirements such as the number of sliders or lifters to be used is also listed in the check list. At this stage, there is still no information on the cooling and ejection design since they are greatly dependent on the final product CAD data. This res earch focuses on the methodology of providing the initial design in 3D solid bas ed on the technical discussion checklist, which takes the role of the overall st andard template since every sub-design has its own standard template. An examp le of a sub-design that has its own standard template is the cavity layout desi gn. The cavity layout for plastic injection moulds can be designed by controlli ng the geometrical parameters using a standardization template. The standardiza tion template for the cavity layout design consists of configurations for the po ssible layouts. Each configuration of the layout design has its own layout desi gn table of all the geometrical parameters. This standardization template is pr e-defined in the layout design level of the mould assembly design. This ensure s that the required configuration can be loaded into the mould assembly design v ery quickly without having the need to redesign the layout. This makes it usefu l for technical discussions between the product designers and mould designers pr ior to the manufacture of the mould. Changes can be made to the 3D cavity layou t design immediately during the discussions thus the savings in time and avo idance of miscommunications.展开更多
Hydraulic simulation is one of the critical methods to research the filling mechanism of molten metal in the casting process.However,it only performs on test pieces with relatively simple structures due to the limitat...Hydraulic simulation is one of the critical methods to research the filling mechanism of molten metal in the casting process.However,it only performs on test pieces with relatively simple structures due to the limitation of the preparation method.In this study,the method of photocuring additive manufacturing was used to prepare the complex casting mould from transparent photosensitive resin.The pouring test was carried out under different centrifugal conditions,and the filling process of the gating system,support bars and other positions in the vertical direction was recorded and analyzed.The experimental results show that the internal liquid level and the filling process of the test piece prepared by this method can be observed clearly.The angle between the liquid surface and the horizontal plane in the test piece gradually increases as the centrifugal rotational speed increases,which means the filling process is carried out from outside to inside at high rotational speed.The velocity of the fluid entering the runner increases with the increase of rotational speed,but the filling speeds is less affected by the centrifugal speed at other positions.The liquid flow is continuous and stable during the forward filling process,without splashing or interruption of liquid droplets.展开更多
This paper focuses on agile manufacturing of complex moulds for punch devices and a decision analysis for the key link of agile manufacturing resources integration—the virtual company in a multivariate criterion univ...This paper focuses on agile manufacturing of complex moulds for punch devices and a decision analysis for the key link of agile manufacturing resources integration—the virtual company in a multivariate criterion universe of discourse. On the basis of presenting an agile manufacturing model of complex moulds for punch devices, we give a fuzzy decision method of two level judgment space of synthetic decision and several key problems which the production of complex moulds for punch devices must face under the architecture hierarchy of agile manufacturing. We give a fuzzy decision method of two level judgment space of synthetic decision and several key problems which the production of complex parts must face under the architecture hierarchy of agile manufacturing.展开更多
Objective:To isolate yeasts and moulds from selected natural systems and study the effect of tetracycline(Tet)on them so as to generate comprehensive data for further elucidation of transfer or evolutionary developmen...Objective:To isolate yeasts and moulds from selected natural systems and study the effect of tetracycline(Tet)on them so as to generate comprehensive data for further elucidation of transfer or evolutionary development of Tet resistance in general and in these lower eukaryotes in particular.Methods:A total of 139 natural yeasts have been isolated from various ecosystems on potato dextrose agar medium.These along with model yeasts and selected natural and model moulds have been tested for their responses to Tet at various concentrations added to the growth media.The effluxed materials were obtained by vortexing and centrifugation of cells and tested against sensitive bacterium.Results:It was found that Tet efflux was a general feature of natural yeasts and filamentous fungi(moulds)could resist Tet upto a concentration of 5 mg/mL.However,at a very high concentration(10 mg/mL)neither the yeasts nor the moulds could grow indicating that Tet is toxic for these eukaryotes at very high concentrations.The presence of Tet in the medium exaggerates filamentation in all the hyphal forming yeasts.Conclusions:The results suggest efflux as the general mechanism of Tet-resistance in yeasts and moulds possibly acquired from bacteria via horizontal transfer.展开更多
This paper focuses on the high-temperature tensile failure mechanism of RTM(resin transfer moulding)-made symmetric and asymmetric composite T-joints.The failure modes as well as the load-displacement curves of symmet...This paper focuses on the high-temperature tensile failure mechanism of RTM(resin transfer moulding)-made symmetric and asymmetric composite T-joints.The failure modes as well as the load-displacement curves of symmetric(three specimens)and asymmetric(three specimens)composite T-joints were determined by tensile tests at room and high temperatures.Progressive damage models(PDMs)of symmetric and asymmetric composite T-joints at room and high temperatures were established based on mixed criteria,and the result predicted from the aforementioned PDMs were compared with experimental data.The predicted initial and final failure loads and failure modes are in good agreement with the experimental results.The failure mechanisms of composite T-joints at different temperatures were investigated by scanning electron microscopy.The results reveal that while the failure mode of asymmetric T-joints at high temperatures resembles that at room temperature,there is a difference in the failure modes of symmetric T-joints.The ultimate failure load of symmetric and asymmetric T-joints at elevated temperatures increases and reduces by 18.4%and 4.97%,albeit with a more discrete distri-bution.This work is expected to provide us with more knowledge about the usability of composite T-joints in elevated temperature environments.展开更多
Variable-fidelity(VF)surrogate models have received increasing attention in engineering design optimization as they can approximate expensive high-fidelity(HF)simulations with reduced computational power.A key challen...Variable-fidelity(VF)surrogate models have received increasing attention in engineering design optimization as they can approximate expensive high-fidelity(HF)simulations with reduced computational power.A key challenge to building a VF model is devising an adaptive model updating strategy that jointly selects additional low-fidelity(LF)and/or HF samples.The additional samples must enhance the model accuracy while maximizing the computational efficiency.We propose ISMA-VFEEI,a global optimization framework that integrates an Improved Slime-Mould Algorithm(ISMA)and a Variable-Fidelity Expected Extension Improvement(VFEEI)learning function to construct a VF surrogate model efficiently.First,A cost-aware VFEEI function guides the adaptive LF/HF sampling by explicitly incorporating evaluation cost and existing sample proximity.Second,ISMA is employed to solve the resulting non-convex optimization problem and identify global optimal infill points for model enhancement.The efficacy of ISMA-VFEEI is demonstrated through six numerical benchmarks and one real-world engineering case study.The engineering case study of a high-speed railway Electric Multiple Unit(EMU),the optimization objective of a sanding device attained a minimum value of 1.546 using only 20 HF evaluations,outperforming all the compared methods.展开更多
Molecular Landers are a class of compounds containing an aromatic board as well as bulky side groups which upon adsorption of the molecule on a surface may lift the molecular board away from the substrate.Different mo...Molecular Landers are a class of compounds containing an aromatic board as well as bulky side groups which upon adsorption of the molecule on a surface may lift the molecular board away from the substrate.Different molecular Landers have extensively been studied as model systems for nanomachines and the formation of molecular wires,as well as for their function as“molecular moulds”,i.e.,acting as templates by accommodating metal atoms underneath their aromatic board.Here,we investigate the adsorption of a novel Lander molecule 1,4-bis(4-(2,4-diaminotriazine)phenyl)-2,3,5,6-tetrakis(4-tert-butylphenyl)benzene(DAT,C_(64)H_(68)N_(10))on Cu(110)and Au(111)surfaces under ultrahigh vacuum(UHV)conditions.By means of scanning tunneling microscopy(STM)imaging and manipulation,we characterize the morphology and binding geometries of DAT molecules at terraces and step edges.On the Cu(110)surface,various contact configurations of individual DAT Landers were formed at the step edges in a controlled manner,steered by STM manipulation,including lateral translation,rotation,and pushing molecules to an upper terrace.The diffusion barrier of single DAT molecules on Au(111)is considerably smaller than on Cu(110).The DAT Lander is specially designed with diamino-triazine side groups making it suitable for future studies of molecular self-assembly by hydrogen-bonding interactions.The results presented here are an important guide to the choice of substrate for future studies using this compound.展开更多
Additives of dioctyl phthalate(DOP),ethylene bis-stearomide(EBS),and epoxy(EP)were selected to modify the surface of 7075 Al alloy powder.Functional groups in DOP and EBS form hydrogen bonds with hydroxyl groups on th...Additives of dioctyl phthalate(DOP),ethylene bis-stearomide(EBS),and epoxy(EP)were selected to modify the surface of 7075 Al alloy powder.Functional groups in DOP and EBS form hydrogen bonds with hydroxyl groups on the surface of Al powder.Additionally,the epoxy groups in the epoxy resin undergo ring-opening reactions with hydroxyl groups.The above interactions increased the compatibility between alloy powder and polyoxymethylene(POM).After sintering,samples containing DOP and EP presented high contents of C and O,while the part with EBS additive exhibited the lowest contents of 0.006 wt.%C and 0.604 wt.%O,respectively.Excessive C tends to accumulate at grain boundaries during sintering.Concurrently,excessive O causes secondary oxidation of aluminium alloy powder,inhibiting the sintering densification process.Therefore,the densities of the samples containing DOP and EP were only 85.52%and 79.01%,respectively.In contrast,using EBS as an additive,high-quality aluminium alloy parts were achieved,with a relative density of 97.64%and a tensile strength of 193 MPa.展开更多
Highly efficient electromagnetic shielding materials have become an increasing requirement for high-power electronic equipment.Nevertheless,there still remains a challenge in achieving excellent elec-tromagnetic inter...Highly efficient electromagnetic shielding materials have become an increasing requirement for high-power electronic equipment.Nevertheless,there still remains a challenge in achieving excellent elec-tromagnetic interference(EMI)shielding performance with low reflection.Herein,a gradient distri-bution of segregated conductive network consisting of edge-selectively carboxylated graphene(ECG)nanosheets and carboxylated multi-walled carbon nanotubes(cMWCNTs)in poly(vinylidene fluoride)(PVDF)nanocomposites was first designed to achieve outstanding low reflective electromagnetic shielding performance.The sheets of PVDF nanocomposites with different contents of hybrid ECG-cMWCNTs were stacked and further hot-pressed to fabricate the layered PVDF nanocomposites.The overall EMI shielding effectiveness(EMI SE)performance could be further improved by increasing the overall thickness and the layer number.With a fixed thickness of 2.0 mm,the PVDF@7.5wt%ECG_(1)-cMWCNTs 3 six-layered nanocom-posites exhibit excellent EMI SE reaching 79.87 dB with an absorption effectiveness(SE A)of 79.62 dB.The excellent EMI SE performance was ascribed to the multiple interface reflection of the segregated conduc-tive network.Meanwhile,the gradient distribution of ECG-cMWCNTs endows the nanocomposites with a strong absorption ability.This work provides a novel strategy for fabricating EMI shielding composites with low reflection for application in portable electronic devices.展开更多
Various sectors of the industry are searching for new materials with specific requirements,providing improved properties.The study presents novel composite materials based on polylactide that have been modified with t...Various sectors of the industry are searching for new materials with specific requirements,providing improved properties.The study presents novel composite materials based on polylactide that have been modified with the organosilicon compound,(3-thiopropyl)polysilsesquioxane(SSQ-SH).The SSQ-SH compound is a mixture of cage structures and not fully condensed random structures.The composite materials were obtained through injection moulding.The study includes a comprehensive characterization of the new materials that analyze their functional properties,such as rheology(MFR),mechanical strength(tensile strength,Charpy impact strength),and thermal properties.SEM microscopic photos were also taken to analyze the microstructure of the samples.The addition of a 5%by-weight organosilicon compound to polylactide resulted in a significant increase in MFR by 73.8%compared to the neat polymer.The greatest improvement in impact strength was achieved for the 5%SSQ-SH/PLA composite,increasing it by 32.0 kJ/m^(2)compared to PLA,which represents an increase of up to 187%.The conducted research confirms the possibility of modifying the properties of the polymer by employing organosilicon compounds.展开更多
[Objective] The aim was to provide reference for the production technolo- gy of cold fresh chicken. [Method] Lactic acid was used as the disinfectant in cooling water, so as to study the effect of disinfection time on...[Objective] The aim was to provide reference for the production technolo- gy of cold fresh chicken. [Method] Lactic acid was used as the disinfectant in cooling water, so as to study the effect of disinfection time on the microbial content and quality of cold fresh chicken. [Result] With disinfection of 20 min, the removal rates of the total colonies, coliforms and moulds reached over 95%. As the disinfec- tion time was further extended, it had no significant effect on the removal effects of the microbial content and could affect the tenderness and color of cold fresh chick- en. [Cendusion] The study provides references for the design and optimization of the production process of cold fresh chicken.展开更多
The microstructure and mechanical properties of Mg-10.1Gd-3.74Y-0.25Zr （mass fraction, %） alloy （GW104 alloy） cast by metal mould casting （MMC） and lost foam casting （LFC） were evaluated, respectively. It is r...The microstructure and mechanical properties of Mg-10.1Gd-3.74Y-0.25Zr （mass fraction, %） alloy （GW104 alloy） cast by metal mould casting （MMC） and lost foam casting （LFC） were evaluated, respectively. It is revealed that different forming modes do not influence the phase composition of as-cast alloy. In the as-cast specimens, the microstructures are similar and composed of α-Mg solid solution, eutectic compound of α-Mg＋Mg 24 （Gd, Y） 5 and cuboid-shaped Mg 5 （Gd, Y） phase; whereas the average grain size of the alloy produced by metal mould casting is smaller than that by lost foam casting. The eutectic compound of the alloy is completely dissolved after solution treatment at 525 ℃for 6 h, while the Mg 5 （Gd, Y） phase still exists after solution treatment. After peak-ageing, the lost foam cast alloy exhibits the maximum ultimate tensile strength of 285 MPa, and metal mould cast specimen 325 MPa at room temperature, while the tensile yield strengths of them are comparable. It can be concluded that GW104 alloy cast by lost foam casting possesses similar microstructure and evidently lower mechanical strength compared with metal mould cast alloy, due to slow solidification rate and proneness to form shrinkage porosities during lost foam casting process.展开更多
Laboratory-scale carbon anodes were produced by a new method of high temperature mould pressing, and their physico-chemical properties were studied. The influence of mould pressing conditions and coal pitch addition o...Laboratory-scale carbon anodes were produced by a new method of high temperature mould pressing, and their physico-chemical properties were studied. The influence of mould pressing conditions and coal pitch addition on the bulk density, crushing strength, and oxidation resistance was analyzed. The mierostructure of carbon anodes was investigated by scanning electron microscopy （SEM）, and the mechanism of producing carbon anodes by high-temperature mould pressing was analyzed. The results show that when the anodes are produced by high-temperature mould pressing, coal pitch can expand into the coke particles and fill the pores inside the particles, which is beneficial for improving the quality of prebaked anodes. The bulk density of carbon anodes is 1.64-1.66 g/cm3, which is 0.08-0.12 g/cm3 higher than that of industrial anodes, and the oxidation resistance of carbon anodes is also significantly improved.展开更多
The microstructures and crystal growth directions of permanent mould casting（PMC） and directionally solidified（DS） Al-Cu alloys with different contents of Cu were investigated. Simultaneously, the effects of pouri...The microstructures and crystal growth directions of permanent mould casting（PMC） and directionally solidified（DS） Al-Cu alloys with different contents of Cu were investigated. Simultaneously, the effects of pouring temperature on the microstructure and crystal growth direction of permanent mould casting pure Al were also discussed. The results indicate that the α（Al） crystals in the pure Al do not always keep common columnar grains, but change from the columnar grains to columnar dendrites with developed arms as the pouring temperature rises. The growth direction also varies with the change of pouring temperature. Cu element has similar effects on the microstructures of the PMC and DS casting Al-Cu alloys and the α（Al） crystals gradually change from columnar crystals in turn to columnar dendrites and developed equiaxed dendrites as the Cu content increases. The crystal growth direction in the PMC alloys gradually approaches （110） orientation with increasing Cu content. But the resulting crystals with growth direction of （110） do not belong to feathery grains. There are also no feathery grains to form in all of the DS Al-Cu alloys.展开更多
基金financially supported by the National Natural Science Foundation of China (No. 52062029)the Key Science and Technology Project of Gansu Province (No. 18YF1GA064)the Natural Science Foundation of Gansu Provence (No. 25JRRA094)。
文摘Investment casting shell moulds are widely applied to cast alloys, but how to efficiently form a hierarchical porous structure inside the wall is an innovation and challenge. In this research, porous shell moulds with three infill patterns(rectilinear, grid, and honeycomb) were prepared using bauxite slurry and slurry extrusionbased additive manufacturing technology, and the effects of infill patterns on the properties were evaluated. The hierarchical pores inside the wall are composed of the macropores formed by infills and the micropores among bauxite particles. Different infill patterns result in changes in distribution and shape of pores, thereby affecting the properties of the shell moulds. The honeycomb pattern has more comprehensive advantages compared to the other two infill patterns. The samples prepared with the honeycomb pattern exhibit the highest bending strength(11.62 MPa) and porosity(41.6%), as well as good heat-transfer ability, with an average shrinkage rate within 2.0%. This work provides an attractive feasibility for fabricating shell moulds with hierarchical porous walls.
文摘Phosphate-bonded investments have already been widely utilized in dental restoration and micro-casting of artistic products for its outstanding rapid setting and high strength. However, the rapid setting rate of investment slurry has up to now been a barrier to extend the use of such slurry in preparation of medium-sized ceramic moulds. This paper proposes a new process of rapid fabrication of magnesia-phosphate-bonded investment ceramic moulds for medium-sized superalloy castings utilizing bauxite and mullite as refractory aggregates. In order to determine the properties of magnesia-phosphate-bonded bauxite-mullite investments (MPBBMI), a series of experiments were conducted, including modifciation of the workable time of slurry by liquid(mL)/powder(g)(L/P) ratio and addition of boric acid as retard agent and sodium tri-polyphosphate (STP) as strengthening agent, and adjustment of bauxite (g)/mullite(g)(B/M) ratio for mechanical strength. Mechanical vibration was applied to improve initial setting time and fluidity when pouring investment slurry; then an intermediate size ceramic mould for superalloy castings was manufactured by means of this rapid preparing process with MPBBMI material. The results showed that the MPBBMI slurry exhibits proper initial setting time and excellent fluidity when the L/P ratio is 0.64 and the boric acid content is 0.88wt.%. The fired specimens made from the MPBBMI material demonstrated adequate compression strength to withstand impact force of molten metal when the B/M ratio is 0.89 and the STP content is 0.92wt.%. The experimental results confirmed the feasibility of the proposed rapid fabricating process for medium-sized ceramic moulds with MPBBMI material by appropriate measures.
基金Beijing Everest Green Building Technology Ltd. for the funding
文摘This study proposes an innovative precast shear wall system, called an EVE precast hollow shear wall structure (EVE-PHSW). Precast panels in EVE-PHSW are simultaneously precast with vertical and horizontal holes. Noncontact lap splices of rebars are used in vertical joints connecting adjacent precast panels for automated prefabrication and easy in situ erection. The seismic behavior of EVE walls was examined through a series of tests on six wall specimens with aspect ratios of 1.0~1.3. Test results showed that EVE wall specimens with inside cast-in situ concrete achieved the desired “strong bending and weak shear” and failed in shear mode. Common main diagonal cracks and brittle shear failure in squat cast-in situ walls were prevented. Inside cast-in situ concrete could signifi cantly improve the shear strength and stiff ness of EVE walls. The details of boundary elements (cast-in situ or prefabricated) and vertical joints (contiguous or spaced) had little eff ect on the global behavior of EVE walls. Noncontact lap splices in vertical joints could enable EVE walls to exhibit stable load-carrying capacity through extensive deformations. Evaluation on design codes revealed that both JGJ 3-2010 and ACI 318-14 provide conservative estimation of shear strength of EVE walls, and EVE walls achieved shear strength reserves comparative to cast-in situ walls. The recommended eff ective stiff ness for cast-in situ walls in ASCE 41-17 appeared to be appropriate for EVE walls.
文摘Unsteady fluid flows and level fluctuations in a thin slab continuous casting mould have significant influence on product quality. In this study, the phenomena concerning transient flow features and free surface motions were analyzed by means of the large eddy simulation （LES） software with the smagorinsky SGS model--VisualCast （VCast） II, where the Simpler algorithm on a body-fitted mesh was used to resolve governing equations. A series of water analog experiments on the fluid flow and the surface wave in the moulds of thin slab continuous casting were also performed. The results of fluid regions, middle of vortex and level fluctuation from digital simulations were identical with the results of the water analog experiments.
文摘In an injection moulding process, the mould cooling s ystem is very important as an efficient and uniform cooling effect can improve b oth the productivity and part quality. Due to the complexity of the process, muc h research on the mould cooling analysis and cooling design optimization has bee n focused on the core and the cavity, excluding other systems of injection mould s. However, the runner system introduces a considerable amount of heat into the mould. In recent years, more and more hot runner systems are being applied in th e moulding industry to save material and decrease losses of injection pressure. This raises the need to include the hot runner system in the cooling analysis. I n this paper, a photo frame part was studied. The mould was built with a hot run ner system. Two thermal sensors were installed: one measures the temperature of lateral surface of hot runner nozzle; the other measures the plastic temperature from the core side. A pressure sensor was also installed to measure the pressur e of the core impression. Cooling analysis was performed using ABAQUS, ananalysi s software based on the Finite Element Method (FEM). The assembly including core , cavity and plastic part was modeled. Heat conduction from hot runner to cavity and from polymer melt to the mould and force convection on the cooling channel surfaces were studied. The natural convection between the ambient air and the ex terior mould surface was ignored. The simulations were adjusted with the experim ental results to find out the heat input from hot runner and its influence on mo uld cooling. Finally, the optimal cooling design and optimal injection condition were obtained.
文摘The characteristic of metallographic structure of the SnSb alloy moulds is that hard particles are distributed on the soft metal matrix. Great difference of the hard particles and the soft metal matrix’hardness makes moulds’polishing become difficult. When a rigid grindstone is used to polish the surface of the SnSb alloy mould, the hard abrasives fall off and are embed in the soft matrix of SnSb alloy and while the process, the grinding chips are able to block the gap on the grindstone surface and enable the grindstone to blunt, which brings about the polished area on the surface of the mould is seriously squeezed and deformed and the crystal lattice of SnSb alloys is seriously distorted, and the work hardening takes place. At the same time, the rigid grindstone is easy to scratch the surface of the SnSb alloy mould. Owing to the above reasons, it is difficult to reduce surface roughness and improve the surface quality of SnSb alloy moulds. Taking use of the CAD/CAM technique and the complex processing of combining electrolyzing polishing and mechanical polishing with the magnetic force, mould’s polishing automation is realized on the numerical control machine tool. This complex processing is finished under a comprehensive action as the following: 1. Electrolyzing polishing action Under the electric field, the electrolyte between the elastic grind wheel and the mould is ionized, which electrolyzes the metal of the mould’s surface. The electrolyzing speed of convex peak on the mould’s surface is faster than that of concave valley, which levels the mould’s surface. 2. Mechanical Polishing action During electrolyzing, a dense passive film of low hardness is formed on the mould’s surface. While polishing, soft grinding wheel scraps the passive film on the conven peak easily, and the new metal surface is exposed, then, a new passive film is formed again, going round and round, the conven peak on the mould’s surface is leveled quickly. 3. Magnetic force action The charged particles in electric field will be acted by the Lorentz force in magnetic field. The field plays a stirring part on electrolyte and reduces electrochemical polarization and concentration polarization, and accelerates the electrochemical reaction. The complex polishing process is not only of high efficiency, but also of good surface quality and provides a good effective method for the non-ferrous metal polishing. When the mould is polished, a speed-raising tool system is used and it can increase the grinding wheel spindle’s speed up to five times. This paper describes the SnSb alloy moulds’polishing steps, grinding wheel speed-raising tool system, polishing principle and the results.
文摘Today, the time-to-market for plastic products ar e getting shorter, thus the lead-time for making the injection mould is decreasin g. There is potential in timesavings in the mould design stage because the design process that is repeatable for every mould design can be standardized. T he preliminary work of any final plastic injection mould design is to always pro vide an initial design of the mould assembly for product designers (customers) p rior to receiving the final product CAD data. Traditionally and even up till no w, this initial design is always created using 2D CAD packages. The information used for the initial design is based on the technical discussion checklist, in which most mould makers have their own standards. This checklist is also being used as a quotation since the most basic information of the mould in the particu lar project is being recorded in it. The basic information in this checklist in cludes the number of cavities, the type of mould base to be used, the moulding m achine to be used for the moulding, the type of gating system, the type of resin material used and its shrinkage value etc. Information on special requirements such as the number of sliders or lifters to be used is also listed in the check list. At this stage, there is still no information on the cooling and ejection design since they are greatly dependent on the final product CAD data. This res earch focuses on the methodology of providing the initial design in 3D solid bas ed on the technical discussion checklist, which takes the role of the overall st andard template since every sub-design has its own standard template. An examp le of a sub-design that has its own standard template is the cavity layout desi gn. The cavity layout for plastic injection moulds can be designed by controlli ng the geometrical parameters using a standardization template. The standardiza tion template for the cavity layout design consists of configurations for the po ssible layouts. Each configuration of the layout design has its own layout desi gn table of all the geometrical parameters. This standardization template is pr e-defined in the layout design level of the mould assembly design. This ensure s that the required configuration can be loaded into the mould assembly design v ery quickly without having the need to redesign the layout. This makes it usefu l for technical discussions between the product designers and mould designers pr ior to the manufacture of the mould. Changes can be made to the 3D cavity layou t design immediately during the discussions thus the savings in time and avo idance of miscommunications.
基金This work was financially supported by the National Science and Technology Major Project of China(Grant No.J2019-Ⅶ-0002-0142)the National Natural Science Foundation of China(Grant No.52175333).
文摘Hydraulic simulation is one of the critical methods to research the filling mechanism of molten metal in the casting process.However,it only performs on test pieces with relatively simple structures due to the limitation of the preparation method.In this study,the method of photocuring additive manufacturing was used to prepare the complex casting mould from transparent photosensitive resin.The pouring test was carried out under different centrifugal conditions,and the filling process of the gating system,support bars and other positions in the vertical direction was recorded and analyzed.The experimental results show that the internal liquid level and the filling process of the test piece prepared by this method can be observed clearly.The angle between the liquid surface and the horizontal plane in the test piece gradually increases as the centrifugal rotational speed increases,which means the filling process is carried out from outside to inside at high rotational speed.The velocity of the fluid entering the runner increases with the increase of rotational speed,but the filling speeds is less affected by the centrifugal speed at other positions.The liquid flow is continuous and stable during the forward filling process,without splashing or interruption of liquid droplets.
文摘This paper focuses on agile manufacturing of complex moulds for punch devices and a decision analysis for the key link of agile manufacturing resources integration—the virtual company in a multivariate criterion universe of discourse. On the basis of presenting an agile manufacturing model of complex moulds for punch devices, we give a fuzzy decision method of two level judgment space of synthetic decision and several key problems which the production of complex moulds for punch devices must face under the architecture hierarchy of agile manufacturing. We give a fuzzy decision method of two level judgment space of synthetic decision and several key problems which the production of complex parts must face under the architecture hierarchy of agile manufacturing.
基金Supported by Madhya Pradesh Council of Science and Technology,Bhopal(Grant No.3902/CST/R&D/2011).
文摘Objective:To isolate yeasts and moulds from selected natural systems and study the effect of tetracycline(Tet)on them so as to generate comprehensive data for further elucidation of transfer or evolutionary development of Tet resistance in general and in these lower eukaryotes in particular.Methods:A total of 139 natural yeasts have been isolated from various ecosystems on potato dextrose agar medium.These along with model yeasts and selected natural and model moulds have been tested for their responses to Tet at various concentrations added to the growth media.The effluxed materials were obtained by vortexing and centrifugation of cells and tested against sensitive bacterium.Results:It was found that Tet efflux was a general feature of natural yeasts and filamentous fungi(moulds)could resist Tet upto a concentration of 5 mg/mL.However,at a very high concentration(10 mg/mL)neither the yeasts nor the moulds could grow indicating that Tet is toxic for these eukaryotes at very high concentrations.The presence of Tet in the medium exaggerates filamentation in all the hyphal forming yeasts.Conclusions:The results suggest efflux as the general mechanism of Tet-resistance in yeasts and moulds possibly acquired from bacteria via horizontal transfer.
基金supported by the Natural Science Foundation of Shanghai(Grant No.24ZR1401700)Fundamental Research Funds for the Central Universities(Grant No.2232022D-28)the Young Elite Scientists Sponsorship Program by the China Association for Science and Technology(Grant No.2016QNRC001).
文摘This paper focuses on the high-temperature tensile failure mechanism of RTM(resin transfer moulding)-made symmetric and asymmetric composite T-joints.The failure modes as well as the load-displacement curves of symmetric(three specimens)and asymmetric(three specimens)composite T-joints were determined by tensile tests at room and high temperatures.Progressive damage models(PDMs)of symmetric and asymmetric composite T-joints at room and high temperatures were established based on mixed criteria,and the result predicted from the aforementioned PDMs were compared with experimental data.The predicted initial and final failure loads and failure modes are in good agreement with the experimental results.The failure mechanisms of composite T-joints at different temperatures were investigated by scanning electron microscopy.The results reveal that while the failure mode of asymmetric T-joints at high temperatures resembles that at room temperature,there is a difference in the failure modes of symmetric T-joints.The ultimate failure load of symmetric and asymmetric T-joints at elevated temperatures increases and reduces by 18.4%and 4.97%,albeit with a more discrete distri-bution.This work is expected to provide us with more knowledge about the usability of composite T-joints in elevated temperature environments.
基金funded by National Natural Science Foundation of China(grant No.52405255)Special Program of Huzhou(grant No.2023GZ05)+1 种基金Projects of Huzhou Science and Technology Correspondent(grant No.2023KT76)Guangdong Basic and Applied Basic Research Foundation(grant No.2025A1515010487)。
文摘Variable-fidelity(VF)surrogate models have received increasing attention in engineering design optimization as they can approximate expensive high-fidelity(HF)simulations with reduced computational power.A key challenge to building a VF model is devising an adaptive model updating strategy that jointly selects additional low-fidelity(LF)and/or HF samples.The additional samples must enhance the model accuracy while maximizing the computational efficiency.We propose ISMA-VFEEI,a global optimization framework that integrates an Improved Slime-Mould Algorithm(ISMA)and a Variable-Fidelity Expected Extension Improvement(VFEEI)learning function to construct a VF surrogate model efficiently.First,A cost-aware VFEEI function guides the adaptive LF/HF sampling by explicitly incorporating evaluation cost and existing sample proximity.Second,ISMA is employed to solve the resulting non-convex optimization problem and identify global optimal infill points for model enhancement.The efficacy of ISMA-VFEEI is demonstrated through six numerical benchmarks and one real-world engineering case study.The engineering case study of a high-speed railway Electric Multiple Unit(EMU),the optimization objective of a sanding device attained a minimum value of 1.546 using only 20 HF evaluations,outperforming all the compared methods.
基金We acknowledge financial support from the IST Pico-Inside and NMP Frontiers European projects as well as grants from the Danish Ministry of Science,Technology and Innovation and from the Danish Research Councils.M.H and Y.B.J thank the CMIFM via the Volubilis France-Morocco exchange program.
文摘Molecular Landers are a class of compounds containing an aromatic board as well as bulky side groups which upon adsorption of the molecule on a surface may lift the molecular board away from the substrate.Different molecular Landers have extensively been studied as model systems for nanomachines and the formation of molecular wires,as well as for their function as“molecular moulds”,i.e.,acting as templates by accommodating metal atoms underneath their aromatic board.Here,we investigate the adsorption of a novel Lander molecule 1,4-bis(4-(2,4-diaminotriazine)phenyl)-2,3,5,6-tetrakis(4-tert-butylphenyl)benzene(DAT,C_(64)H_(68)N_(10))on Cu(110)and Au(111)surfaces under ultrahigh vacuum(UHV)conditions.By means of scanning tunneling microscopy(STM)imaging and manipulation,we characterize the morphology and binding geometries of DAT molecules at terraces and step edges.On the Cu(110)surface,various contact configurations of individual DAT Landers were formed at the step edges in a controlled manner,steered by STM manipulation,including lateral translation,rotation,and pushing molecules to an upper terrace.The diffusion barrier of single DAT molecules on Au(111)is considerably smaller than on Cu(110).The DAT Lander is specially designed with diamino-triazine side groups making it suitable for future studies of molecular self-assembly by hydrogen-bonding interactions.The results presented here are an important guide to the choice of substrate for future studies using this compound.
基金supported by the National Key Research and Development Program of China(No.2021YFB3701900)。
文摘Additives of dioctyl phthalate(DOP),ethylene bis-stearomide(EBS),and epoxy(EP)were selected to modify the surface of 7075 Al alloy powder.Functional groups in DOP and EBS form hydrogen bonds with hydroxyl groups on the surface of Al powder.Additionally,the epoxy groups in the epoxy resin undergo ring-opening reactions with hydroxyl groups.The above interactions increased the compatibility between alloy powder and polyoxymethylene(POM).After sintering,samples containing DOP and EP presented high contents of C and O,while the part with EBS additive exhibited the lowest contents of 0.006 wt.%C and 0.604 wt.%O,respectively.Excessive C tends to accumulate at grain boundaries during sintering.Concurrently,excessive O causes secondary oxidation of aluminium alloy powder,inhibiting the sintering densification process.Therefore,the densities of the samples containing DOP and EP were only 85.52%and 79.01%,respectively.In contrast,using EBS as an additive,high-quality aluminium alloy parts were achieved,with a relative density of 97.64%and a tensile strength of 193 MPa.
基金support from the Sichuan Science and Technology Program(2022YFH0090)and the Fundamental Research Funds for the Central Universities.
文摘Highly efficient electromagnetic shielding materials have become an increasing requirement for high-power electronic equipment.Nevertheless,there still remains a challenge in achieving excellent elec-tromagnetic interference(EMI)shielding performance with low reflection.Herein,a gradient distri-bution of segregated conductive network consisting of edge-selectively carboxylated graphene(ECG)nanosheets and carboxylated multi-walled carbon nanotubes(cMWCNTs)in poly(vinylidene fluoride)(PVDF)nanocomposites was first designed to achieve outstanding low reflective electromagnetic shielding performance.The sheets of PVDF nanocomposites with different contents of hybrid ECG-cMWCNTs were stacked and further hot-pressed to fabricate the layered PVDF nanocomposites.The overall EMI shielding effectiveness(EMI SE)performance could be further improved by increasing the overall thickness and the layer number.With a fixed thickness of 2.0 mm,the PVDF@7.5wt%ECG_(1)-cMWCNTs 3 six-layered nanocom-posites exhibit excellent EMI SE reaching 79.87 dB with an absorption effectiveness(SE A)of 79.62 dB.The excellent EMI SE performance was ascribed to the multiple interface reflection of the segregated conduc-tive network.Meanwhile,the gradient distribution of ECG-cMWCNTs endows the nanocomposites with a strong absorption ability.This work provides a novel strategy for fabricating EMI shielding composites with low reflection for application in portable electronic devices.
基金supported by the Smart Growth Operational Programme(No.POIR.04.02.00-00-D003/20-00)European Funds(No.RPWP.01.01.00-30-0004/18)Ministry of Science and Higher Education(No.21/529535/SPUB/SP/2022).
文摘Various sectors of the industry are searching for new materials with specific requirements,providing improved properties.The study presents novel composite materials based on polylactide that have been modified with the organosilicon compound,(3-thiopropyl)polysilsesquioxane(SSQ-SH).The SSQ-SH compound is a mixture of cage structures and not fully condensed random structures.The composite materials were obtained through injection moulding.The study includes a comprehensive characterization of the new materials that analyze their functional properties,such as rheology(MFR),mechanical strength(tensile strength,Charpy impact strength),and thermal properties.SEM microscopic photos were also taken to analyze the microstructure of the samples.The addition of a 5%by-weight organosilicon compound to polylactide resulted in a significant increase in MFR by 73.8%compared to the neat polymer.The greatest improvement in impact strength was achieved for the 5%SSQ-SH/PLA composite,increasing it by 32.0 kJ/m^(2)compared to PLA,which represents an increase of up to 187%.The conducted research confirms the possibility of modifying the properties of the polymer by employing organosilicon compounds.
基金Supported by the Jiangsu Agricultural Science and Technology Innovation Foundation(CX(15)1009)~~
文摘[Objective] The aim was to provide reference for the production technolo- gy of cold fresh chicken. [Method] Lactic acid was used as the disinfectant in cooling water, so as to study the effect of disinfection time on the microbial content and quality of cold fresh chicken. [Result] With disinfection of 20 min, the removal rates of the total colonies, coliforms and moulds reached over 95%. As the disinfec- tion time was further extended, it had no significant effect on the removal effects of the microbial content and could affect the tenderness and color of cold fresh chick- en. [Cendusion] The study provides references for the design and optimization of the production process of cold fresh chicken.
基金Project(2007CB613704)supported by the National Basic Research Program of China
文摘The microstructure and mechanical properties of Mg-10.1Gd-3.74Y-0.25Zr （mass fraction, %） alloy （GW104 alloy） cast by metal mould casting （MMC） and lost foam casting （LFC） were evaluated, respectively. It is revealed that different forming modes do not influence the phase composition of as-cast alloy. In the as-cast specimens, the microstructures are similar and composed of α-Mg solid solution, eutectic compound of α-Mg＋Mg 24 （Gd, Y） 5 and cuboid-shaped Mg 5 （Gd, Y） phase; whereas the average grain size of the alloy produced by metal mould casting is smaller than that by lost foam casting. The eutectic compound of the alloy is completely dissolved after solution treatment at 525 ℃for 6 h, while the Mg 5 （Gd, Y） phase still exists after solution treatment. After peak-ageing, the lost foam cast alloy exhibits the maximum ultimate tensile strength of 285 MPa, and metal mould cast specimen 325 MPa at room temperature, while the tensile yield strengths of them are comparable. It can be concluded that GW104 alloy cast by lost foam casting possesses similar microstructure and evidently lower mechanical strength compared with metal mould cast alloy, due to slow solidification rate and proneness to form shrinkage porosities during lost foam casting process.
基金Project(090302012)supported by the Fundamental Research Funds for the Central Universities,ChinaProject(50934005)supported by the National Natural Science Foundation of China
文摘Laboratory-scale carbon anodes were produced by a new method of high temperature mould pressing, and their physico-chemical properties were studied. The influence of mould pressing conditions and coal pitch addition on the bulk density, crushing strength, and oxidation resistance was analyzed. The mierostructure of carbon anodes was investigated by scanning electron microscopy （SEM）, and the mechanism of producing carbon anodes by high-temperature mould pressing was analyzed. The results show that when the anodes are produced by high-temperature mould pressing, coal pitch can expand into the coke particles and fill the pores inside the particles, which is beneficial for improving the quality of prebaked anodes. The bulk density of carbon anodes is 1.64-1.66 g/cm3, which is 0.08-0.12 g/cm3 higher than that of industrial anodes, and the oxidation resistance of carbon anodes is also significantly improved.
基金Project(51061010)supported by the National Natural Science Foundation of ChinaProject(NCET-10-0023)supported by the Program for New Century Excellent Talents in University of ChinaProject(J201103)supported by the Program for Hongliu Outstanding Talents of Lanzhou University of Technology,China
文摘The microstructures and crystal growth directions of permanent mould casting（PMC） and directionally solidified（DS） Al-Cu alloys with different contents of Cu were investigated. Simultaneously, the effects of pouring temperature on the microstructure and crystal growth direction of permanent mould casting pure Al were also discussed. The results indicate that the α（Al） crystals in the pure Al do not always keep common columnar grains, but change from the columnar grains to columnar dendrites with developed arms as the pouring temperature rises. The growth direction also varies with the change of pouring temperature. Cu element has similar effects on the microstructures of the PMC and DS casting Al-Cu alloys and the α（Al） crystals gradually change from columnar crystals in turn to columnar dendrites and developed equiaxed dendrites as the Cu content increases. The crystal growth direction in the PMC alloys gradually approaches （110） orientation with increasing Cu content. But the resulting crystals with growth direction of （110） do not belong to feathery grains. There are also no feathery grains to form in all of the DS Al-Cu alloys.
