Influence of introducing Zr,Ti,Nb and Ce elements on externally solidified crystals and mechanical properties of high-pressure die-casting Al–Si alloy

High pressure die casting(HPDC)AlSi10Mn Mg alloy castings are widely used in the automobile industry.Mg can optimize the mechanical properties of castings through heat treatment,while the release of thermal stress arouses the deformation of large integrated die-castings.Herein,the development of non-heat treatment Al alloys is becoming the hot topic.In addition,HPDC contains externally solidified crystals(ESCs),which are detrimental to the mechanical properties of castings.To achieve high strength and toughness of non-heat treatment die-casting Al-Si alloy,we used AlSi9Mn alloy as matrix with the introduction of Zr,Ti,Nb,and Ce.Their influences on ESCs and mechanical properties were systematically investigated through three-dimensional reconstruction and thermodynamic simulation.Our results reveal that the addition of Ti increased ESCs'size and porosity,while the introduction of Nb refined ESCs and decreased porosity.Meanwhile,large-sized Al_3(Zr,Ti)phases formed and degraded the mechanical properties.Subsequent introduction of Ce resulted in the poisoning effect and reduced mechanical properties.

Microstructure and mechanical properties of Mg-6Gd-3Y-0.5Zr alloy processed by high-vacuum die-casting

GW63K （Mg-6Gd-3Y-0.5Zr） magnesium alloys were prepared successfully by high-vacuum die-casting. Effects of fast shot speed and vacuum level on the grain size and mechanical properties of this alloy were studied. Microstructure of the alloys was analyzed by SEM, EDX and optical microscope （OM）. The effect of heat treatment on high vacuum die-casting （HVDC） GW63K alloy was also studied. The results indicate that with the increase of fast velocity, the tensile yield strength hardly changes, but the elongation first increases, then decreases. The optimum heat treatment process is solution treatment at 748 K for 2 h and aging at 473 K for 80 h. Under this condition, GW63K magnesium alloy exhibits a maximum tensile strength and elongation of 308 MPa and 9.45%. There is significant correlation between ductility and the presence of external solidified cells （ESCs）. The as-cast GW63K alloy consists ofα-Mg and Mg24（Gd,Y）5 particles. After heat treatment, Gd and Y atoms dissolve intoα-Mg matrix.

A review of magnesium die-castings for closure applications

Vehicle mass reduction in the automotive industry has become an industry-wide objective.Increasing fuel efficiency and greenhouse gas emission targets for engine-powered vehicles,and ambitions for extended range electric vehicles have motivated these reductions in vehicle mass.Mass reduction opportunities in structural automotive applications are increasingly realized through lightweight alloy castings,such as magnesium,primarily due to the ease of component substitution.The traditional benefits of magnesium die-castings including lightweighting and associated compounded mass savings,excellent strength-to-weight ratio,part consolidation,near net-shape forming,dimensional repeatability,and integration of additional components can be realized in closure applications.One recent example is the application of a magnesium die-casting for the structural inner of the liftgate in the 2017 Chrysler Pacifica,replacing nine parts in the previous generation and resulting in a liftgate assembly weight reduction of nearly 50%.The work presented here reviews past and current developments of magnesium die-castings in closure applications and discusses the benefits and challenges of magnesium alloys for these applications,including casting design,corrosion and fastening strategies,and the manufacturing design and assembly methodologies.

Development of vacuum die-casting process

The vacuum die-casting process,started 25 years ago in Japan,has been widely applied.This technology contributes very much to improvement of castings quality.The main factor causing the defects of die castings is the trapped air in the mold cavity,while the key technology of vacuum die-casting process is to avoid the trapped air effectively by evacuating the cavity before casting.At the same time,due to the shot speed and the casting pressure reduced in half,the service life of the die is prolonged and the productivity is enhanced,as well.Vacuum die-casting process is of great signif icance in improving the die castings quality and making up the shortcomings of super-high-speed shot casting.

Simulation of α-Al grain formation in high vacuum die-casting Al-Si-Mg alloys with multi-component quantitative cellular automaton method

Al-Si-Mg alloys are the most commonly used material in high vacuum die-casting(HVDC),in which the morphology and distribution ofα-Al grains have important effect on mechanical properties.A multi-component quantitative cellular automaton(CA)model was developed to simulate the microstructure and microsegregation of HVDC Al-Si-Mg alloys with different Si contents(7%and 10%)and cooling rates during solidification.The grain number and average grain size with electron backscatter diffraction(EBSD)analysis were used to verify the simulation.The relationship between grain size and nucleation order as well as nuclei density was investigated and discussed.It is found that the growth of grains will be restrained in the location with higher nuclei density.The influence of composition and cooling rate on the solute transport reveals that for AlSi7Mg0.3 alloy the concentration of solute Mg in liquid is higher at the beginning of eutectic solidification.The comparison between simulation and experiment results shows that externally solidified crystals(ESCs)have a significant effect for samples with high cooling rate and narrow solidification interval.

Thin-Wall Aluminum Die-Casting Technology for Development of Notebook Computer Housing

Silicon-based aluminum casting alloys are known to be one of the most widely used alloy systems mainly due to their superior casting characteristics and unique combination of mechanical and physical properties. However,manufacturing of thin-walled aluminum die-casting components,less than 1.0 mm in thickness,is generally known to be very difficult task to achieve aluminum casting alloys with high fluidity.Therefore,in this study,the optimal die-casting conditions for producing 297 mm×210 mm×0.7 mm thin-walled aluminum component was examined experimentally by using 2 different gating systems,tangential and split type,and vent design.Furthermore,computational solidification simulation was also conducted.The results showed that split type gating system was preferable gating design than tangential type gating system at the point of view of soundness of casting and distortion generated after solidification.It was also found that proper vent design was one of the most important factors for producing thin-wall casting components because it was important for the fulfillment of the thin-wall cavity and the minimization of the casting distortion.

Mold Filling and Prevention of Gas Entrapment in High-pressure Die-casting

This paper presents some results of direct observation of mold filling in a specially designed die-casting by X-ray diffraction, including comparison with numerical simulation. Based on such work the authors discuss how to prevent gas entrapment and propose new methods.

Opportunities and challenges of Chinese die-casting market

The present status and perspectives of Chinese die-casting market were commented. In 2003, the total output of die castings in the whole country was 708000 tons, in which the outputs of Al-alloy, Zn-alloy, Mg-alloy, Cu-alloy die castings were 474600 tons, 222000 tons, 5800 tons, 5600 tons, respectively, each accounted for 67%, 31.35%, 0.85%, 0.8% of the total. The annual sale volume of die-casting machines was approximately 1800. And the gross output value of dies approached RMB 38 billion, in which die-casting dies accounted for about 10%. In the die-casting industry of the entire country, the foreign capital enterprises, public-run enterprises, township and village enterprises, private enterprises accounted for over 80% of the total die-casting enterprises. Super huge die-casting groups are forming.

Development and Application of Die-Casting High Speed Steel Rolls

Due to its high hardness,good red hardness and excellent wear resistance at high temperature,high speed steel(HSS)is fit for the roll manufacture.In order to overcome the segregation of centrifugal casting of HSS roll,die-cast processes were developed and its effects on the properties of the HSS roll were investigated.It was found that pressure,pressing time and speed are three important factors affecting shrinkage cavity.For pouring temperature of 1 400-1 450 ℃,pressure of 150-160 MPa,pressing time of 120-150 sand pressing speed of 14-16mm/s,a compact HSS roll was obtained,which has no segregation and small working allowance.In the high speed wire rod rolling mill,service life of the HSS roll is 5to 8times longer than that of high nickel chromium infinite chilled cast iron roll.

Code generation and recognition using a modified ejection system in die-casting process

A code-generation and recognition technology that uses a modified ejection system in the diecasting process is presented.To achieve the highest level of quality management,the first requirement in the manufacturing process is to establish a product management system according to the specific product unit.Thus,a method to individually identify each product,such as a barcode or QR code,is required during the production process.Products manufactured in the die-casting process always have ejector pin(EP)marks.Herein,an ejection system was modified to generate a unique code using EP marks.This ejection system has two features:an EP with a modified head to show the direction of rotation,and a function to dependently rotate EPs(five or six EPs)with a constant angle.The EPs are numbered according to the rotation angle.Thus,the EP marks can be viewed as a five-or six-digit code.A program was also developed to individually identify the products by automatically detecting and reading the EPs using deep learning-based object detection and classification technology.

Two semi-solid die-casting production lines of Xuzhou Die- casting Technology Co., Ltd. officially put into operation

The two production lines for the first phase of the semi-solid die-casting high-end parts project were put into production in this October, and can monthly produce more than 30 thousand die casting parts.

Assessing efficacy of standard impregnation techniques on die-cast aluminum alloys using X-ray micro-CT

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.

农业拖拉机尾灯多色注塑模具设计

以农业拖拉机尾灯为研究对象,分析了尾灯的内部结构和工艺性,并针对双色模具的特殊性,分析了模具成型方案和设计流程,基于AutoCAD和CAE软件完成了尾灯双色塑件模具的设计。开模试验表明:该产品符合设计需求,整个产品结构稳定,透明度好,设计的模具结构合理、工艺流程可靠,能够满足实际的生产应用,工程应用价值较高。

Microstructure and mechanical properties of Mg-Gd-Y-Zr alloy cast by metal mould and lost foam casting

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.

Production of carbon anodes by high-temperature mould pressing

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.

Effects of on-line solution and off-line heat treatment on microstructure and hardness of die-cast AZ91D alloy

The effects of on-line solution, off-line solution and aging heat treatment on the microstructure and hardness of the die-cast AZ91D alloys were investigated. Brinell hardness of die-cast AZ91D alloy increases through on-line solution and off-line aging treatment but decreases after off-line solution treatment. By X-ray diffractometry, optical microscopy, differential thermal analysis, scanning electron microscopy and X-ray energy dispersive spectroscopy, it is found that the microstructures of the die-cast AZ91D magnesium alloy before and after on-line solution and off-line aging are similar, consisting of α-Mg and β-Al12Mg17. The precipitation of Al element is prevented by on-line solution so that the effect of solid solution strengthening is enhanced. The β-Al12Mg17 phases precipitate from supersaturated Mg solid solution after off-line aging treatment, and lead to microstructure refinement of AZ91D alloy, so the effect of precipitation hardening is enhanced. The β-Al12Mg17 phases dissolve in the substructure after off-line solution treatment, which leads to that the grain boundary strengthening phase is reduced significantly and the hardness of die cast AZ91D is reduced.

Study on Blade Mould CAD/CAM for Hydrodynamic Torque COnverters

Aim To develop blade mould CAD/CAM system of torque converter. Methods The mouldconsisted of four parts and an interactive computer program was developed to design a blade mould of torque converter based on UG at workstation. Results As compar- ed to manual modeling, it is showed in the application that this means not only improves the accuracy of blade shape and manufacture efficiency of converter, but also reduces costs. Conclusion It is proved that this CAD/CAM system is successful, and it opens up widely prospects for design and manufacture of the blade elementsand their moulds.

Solvent de binding of water soluble binder in powder injection moulding

The solvent debinding of water soluble binder in powder injection moulding (MIM) was investigated systematically, including the effects of solvent types, temperature and the thickness of green parts on the solvent debinding rate. After studying the debinding of a green part with a thickness of 4.26 mm, it was found that, the debinding rate of polyethylene glycol(PEG) in water and alcohol was high initially, and then decreased; however, it would increase with temperature increasing. At room temperature, the dissolution rate of PEG in water was higher than that in alcohol, but the latter would be much faster with temperature increasing because the debinding activation energy in alcohol was 51.44 kJ·mol -1 ·K -1 , much higher than 24.23 kJ·mol -1 ·K -1 in water. With a green part thickness larger than 4.26 mm, the debinding was controlled by diffusion; but with that smaller than 2.36 mm, the debinding was controlled by both dissolution and diffusion.

Development tendencies of moulding and core sands

Further development of the technology for making moulding and core sands will be strictly limited by tough requirements due to protection of the natural environment. These tendencies are becoming more and more tense, so that we will reach a point when even processes, that from technological point of view fulfill high requirements of the foundry industry, must be replaced by more ecologically-friendly solutions. Hence, technologies using synthetic resins as binding materials will be limited. This paper presents some predictable development tendencies of moulding and core sands. The increasing role of inorganic substances will be noticed, including silicate binders with significantly improved properties, such as improved knock-out property or higher reclamation strength. Other interesting solutions might also be moulding sands bonded by geo-polymers and phosphate binders or salts and also binders based on degradable biopolymers. These tendencies and the usefulness of these binders are put forward in this paper.