Compression properties of cost-efficient porous expanded clay reinforced AA7075 syntactic foams fabricated by industrial-oriented die casting technology

In today’s manufacturing industries,hard competition between rival firms makes it compulsory for researchers to design lighter and cheaper machine components due to the megatrends of cost-effectiveness and anti-pollution.At this point,aluminum syntactic foams(ASFs)are new-generation engineering composites and come into the upfront as a problem-solver.Owing to their features like low density,sufficient elongation,and perfect energy absorption ability,these advanced foams have been considerably seductive for many industrial sectors nowadays.In this study,an industrial-oriented automatic die casting technology was used for the first time to manufacture the combination of AA7075/porous expanded clay(PEC).Micro evaluations(optical and FESEM)reveal that there is a homogenous particle distribution in the foam samples,and inspections are compatible with the other ASF studies.Additionally,T6 aging heat treatment was operated on one half of the produced foams to explore the probable impact of aging on the compressive responses.Attained results show that PEC particles can be an alternative to expensive hollow spheres used in the previous works.Besides,a favorable relationship is ascertained between the aging treatment and mechanical properties such as compression strength and plateau strength.

Effects of magnesium and copper additions on tensile properties of Al-Si-Cr die casting alloy under as-cast and T5 conditions

Aluminum high pressure die casting(HPDC)technology has evolved in the past decades,enabling stronger and larger one-piece casting with significant part consolidation.It also offers a higher design freedom for more mass-efficient thin-walled body structures.For body structures that require excellent ductility and fracture toughness to be joined with steel sheet via self-piercing riveting(for instance,shock towers and hinge pillars,etc.),a costly T7 heat treatment comprising a solution heat treatment at elevated temperatures(450℃-500℃)followed by an over-ageing heat treatment is needed to optimize microstructure for meeting product requirement.To enable cost-efficient mass production of HPDC body structures,it is important to eliminate the expensive T7 heat treatment without sacrificing mechanical properties.Optimizing die cast alloy chemistry is a potential solution to improve fracture toughness and ductility of the HPDC components.The present study intends to tailor the Mg and Cu additions for a new Al-Si-Cr type die casting alloy(registered as A379 with The Aluminum Association,USA)to achieve the desired tensile properties without using T7 heat treatment.It was found that Cu addition should be avoided,as it is not effective in enhancing strength while degrades tensile ductility.Mg addition is very effective in improving strength and has minor impact on tensile ductility.The investigated Al-Si-Cr alloy with a nominal composition of Al-8.5wt.%Si-0.3wt.%Cr-0.2wt.%Fe shows comparable tensile properties with the T7 treated AlSi10MnMg alloy which is currently used for manufacturing shock towers and hinge pillars.

Focusing on Technology and Services,Competing in China Die Casting Market Report on visits with five companies participating in the Asia-pacific Die Casting Industry Exhibition 2005

The Asia-Pacific Die Casting Industry Exhibition 2005. organized by Foundry Institution of Chinese Mechanical Engineering: Society (FICMES). was held in INTEX Shanghai, China on August 14-17. 2005. On August 16th. the journalists of CHINA FOUNDRY journal visited five exhibitors on the spot of exhibition. They are: Mr. Roland FINK. General manager of Frech (Shanghai) Die Casting Machine Co. Ltd.; Mr. Thomas STROBL. General manager of Buhler Equipment Engineering (Wuxi) Co. Ltd., Switzerland; Mr. WANG Tong. Manager of ABB Engineering (Shanghai) Co. Ltd : Ms Karen LUO. National Sales Manager-Die Casting. Chem-Trend (Shanghai) Trading Co. Ltd.; and Mr. David ZHOU. Sales Supervisor of Acheson. the National Starch & Chemical (Shanghai) Company1. Interview with Mr. Rolalnd FINK, General Manager, Freeh (Shanghai) Die Casting Machine Co. Ltd., and Mr. WU Hao-sen, Representative of Shanghai Office, Freeh ChinaReporter: The die casting machines Of Oskai Freeh GmbH are famous id the world. In order to let more renders know Oskar Frech GmbH. please intrkdluce its basic conditions.Mr. FINK. Oskar Frech GmbH was founded in 1949 and now has mure than 500 employees. It is a world-famous company specialized in research of die casting technology and manufacturing complete sets of equipment. There are a considerable number of Frech's products in the world die casting industry. Especially in the field of magnesium alloy die casting. Freeh's equipment are extensively employed, occupying the large part of the market. The assorted parts are available for Frech's equipment and customers can freely choose them. Frech produces not only hot chamber die casting machines bun also cold chamber die casting machines. Freeh continues to innovate or adopt new technologies lor die casting machines. Owing to the stable and reliable performances, Frech die casting machines are not only employed for production, hut also extensively served as experimental equipment. Either Frech cold chamber die casting machines or hot chamber die casting machines have real-time control (RC)ystems for injection. In 1980. Frech far Last Ltd. was established in Hong Kong by Oskar Frech GmbH. In 1987. Shanghai Office. Frech China was set up. And in May 2005. Frech built its subsidiary factory in Shanghai, to better serve for China and the whole Asia market.Reporter: Please introduce the performances and main features of die casting machines.Mr. FINK: Frech die casting machines are classified into different series for aluminum alloys, magnesium alloys and zinc alloys, respectively. The locking forces are from 20 tons to 2 000 tons. In 1966. Frech built the first hot chamber die easting machine for magnesium in the world. Now we have more than 40 years of experiences m the manufacture of magnesium die casting machines. Frech's equipment have such advantages as high service efficiency and excellent quality. Frech continues to develop and adopt advanced technologies for the security system, die locking system, injection system. control system and hydraulic system of die casting machines. In addition, the funcktional interfaces of Frech die casting machines are complete and the entire structure designs are reasonable. Frech die easting machines have large safety coefficients, stable performancesand long service life. As far as die casting dies are concerned. Frech has kept and developed its own tool room for die manufacturing, which can help customers solvc many problems of mould design and improve the quality of die castings.Reporter: This year Frech built the production factiory. in Shanghai, and this time Frech is joining the die casting exhibition in such a largescale.It is reflected that Frech is ambitious to develop itself in the China die casting market.Mr. FINK: In the past ten years, more than 200 die casting equipment of our company have been supplied to China, Up to present, we have built the production factoryo. in Shanghai, namely frech (Shanghai) Die Casting Machine Co. Ltd. This company uses the parts and components which are all produced originally in German factories to assemble die casting machines. So the performances and qualities of die casting machines produced in Shanghai are kept unchanged, but their prices are greatly reduced, being hetter suitable for the Chinese and Asian markets. Since June this year. some hot chamber die casting machines in locking forces from 20 tons to .315 tons have been assembled in Frech (Shanghai) Die Casting Machine Co.Ltd. And we are also ready to produce cold chamber die casting machines.Then we will gradually enlarge the production scale. Another importantthing is that we are preparing in the shortest time to provide our services after sale and the desired spare parts for our customers.Interview with Mr, Roland FINK. General Manager of Frech (Shanghai) Die Casting Machine Co Ltd .and Mr.WU Hao-sen. Representattive of Shanghai Offive,Frech China.2. Interview with Mr. Thomas STROBL, General Manager of Buhler Equipment Engineering (Wuxi) Co. Ltd., SwitzerlandReporter Mr. Thomas STOBER, How many times are there for your company to participate in the die casting exhibitions organized by Foundry Institution of Chinese Mechanical Fngineering Society?How do you think of this exhibition?Mr. STROBL: Buhler has taken pan in such exhibitions for five times. Certainly, this time the investment is the largest. since this is the first time for the real Buhler machine to be displayed. The displayed machine was made in Wuxi. China. The exhibition is very good.

Study on Numerical Simulation of Mold Filling and Heat Transfer in Die Casting Process

A 3-D mathematical model considering turbulence phenomena has been established based on a computational fluid dynamics technique, so called 3-D SOLA-VOF (Solution Algorithm-Volume of Fluid), to simulate the fluid flow of mold filling process of die casting. In addition, the mathematical model for simulating the heat transfer in die casting process has also been established. The computation program has been developed by the authors with the finite difference method (FDM) recently. As verification, the mold filling process of a S-shaped die casting has been simulated and the simulation results coincide with that of the benchmark test. Finally, as a practical application, the gating design of a motorcycle component was modified by the mold filling simulation and the dies design of another motorcycle component was optimized by the heat transfer simulation. All the optimized designs were verified by the production practice.

Characterization on the formation of porosity and tensile properties prediction in die casting Mg alloys

The 3D visualization of the porosity in high-pressure die casting(HPDC)Mg alloys AZ91D and Mg4Ce2Al0.5Mn(EA42)was investigated by X-ray computed tomography.It was demonstrated that the volumetric porosity at the near-gate location for alloy EA42 was significantly higher than that far from the gate location.This difference resulted from the low valid time during intensified casting pressure conditions.Specimens of alloy EA42 exhibited a narrow pore distribution in the side view(~0.5 mm)compared to the wide distribution(~1.8 mm)of alloy AZ91D,which was mainly attributed to the formation mechanism of the defect band.The formation of microporosity in the defect band of alloy EA42 was inhibited because of the significant latent heat released by a large amount of the Al11Ce3phase segregated in the defect band during solidification.Additionally,an effective estimator(Z-Propagation)was introduced,which is proposed to predict the projected area fraction of the porosity(f)involved during tensile failure with better effectiveness compared with traditional methods based on the actual fractured surface.By coupling the Z-Propagation method with the critical local strain model,the logarithmic fracture strain and true fracture stress of the specimens were predicted within 3.03%and 1.65%of the absolute value of the average relative error(AARE),respectively.

Determination of interfacial heat transfer coefficient and its application in high pressure die casting process

In this paper,the research progress of the interfacial heat transfer in high pressure die casting(HPDC)is reviewed.Results including determination of the interfacial heat transfer coefficient(IHTC),influence of casting thickness,process parameters and casting alloys on the IHTC are summarized and discussed.A thermal boundary condition model was developed based on the two correlations:(a)IHTC and casting solid fraction and(b)IHTC peak value and initial die surface temperature.The boundary model was then applied during the determination of the temperature field in HPDC and excellent agreement was found.

Design and Verification of an Auxiliary System for High Vacuum Die Casting

Vacuum die casting is the optimal method to produce high quality aluminum alloy components.At present,there are still very few systematic studies on vacuum die casting theory and equipment design.On the basis of the existing theories of the vacuum die casting pumping and venting systems,a simplified model is established in this research.The model has an aggregate unit consisted of ＂vacuum pump ＋ buffer tank＂ and a cylindrical container（including the shot sleeve,cavity and exhaust channel）.The theoretical analysis is carried out between the cavity pressure and the pumping time under different volume models.An auxiliary system for high vacuum die casting is designed based on the above analysis.This system is composed of a vacuum control machine and a new vacuum stop valve.The machine has a human-computer control mode with ＂programmable logic controller（PLC） ＋ touch screen＂ and a real-time monitoring function of vacuum degree for buffer tank and die cavity.The vacuum stop valve with the ＂compressed gas ＋ piston rod ＋ labyrinth groove＂ structure can realize the function of whole-process vacuum venting.The new system shows great advantages on vacuuming the cavity with a much faster speed by making tests on an existing die casting mold and a 250 t die casting machine.A die cavity pressure less than 10 kPa can be reached within 0.8 s in the experiment and the porosity of castings can be greatly decreased.The systematic studies on vacuum die casting theory and equipment have a great guiding significance for high vacuum die casting,and can also be applied to other high vacuum forming in related theoretical and practical research.

Die Casting Mold Design of the Thin-walled Aluminum Case by Computational Solidification Simulation

Recently, demand for the lightweight alloy in electric/electronic housings has been greatly increased. However, among the lightweight alloys, aluminum alloy thin-walled die casting is problematic because it is quite difficult to achieve sufficient fluidity and feedability to fill the thin cavity as the wall thickness becomes less than 1mm. Therefore, in this study, thin-walled die casting of aluminum （Al-Si-Cu alloy： ALDC 12） in size of notebook computer housing and thickness of 0.8 mm was investigated by solidification simulation （MAGMA soft） and actual casting experiment （Buhler Evolution B 53D）. Three different types of gating design, finger, tangential and split type with 6 vertical runners, were simulated and the results showed that sound thin-walled die casting was possible with tangential and split type gating design because those gates allowed aluminum melt to flow into the thin cavity uniformly and split type gating system was preferable gating design comparing to tangential type gating system at the point of view of soundness of casting and distortion generated after solidification. Also, the solidification simulation agreed well with the actual die-casting and the casting showed no casting defects and distortion.

LOW CYCLE FATIGUE BEHAVIOR OF AZ91HP ALLOY IN AS HIGHP RESSURE DIE CASTING

Fully reversed total strain-controlled low-cycle fatigue tests were conducted at room temperature in air to study the fatigue behavior of AZ91HP magnesium alloy in as high pressure die casting and subsequently heat treatment. All the specimens in different heat histories exhibit cyclic strain hardening in different degrees. It is difficult to distinguish the fatigue behavior of the die casting specimens from that of the solution aging specimens. The solution treated specimens show longer fatigue life at high strain amplitude and shorter fatigue life at low strain amplitude than the die casting and solution aging specimens though they have the lowest yield strength with higher strain hardening. Fatigue fracture surfaces for strain amplitude larger than 0.005 show very similar to those found by monotonic tensile tests. The SEM examination reveals that the regions of fatigue crack growth and final fracture can be characterized by quasi-cleavage mechanisms, but some shallow dimples, slip bands and secondary cracks are found on the fracture surface in the fracture crack growth areas.

High thermal conductivity and high strength magnesium alloy for high pressure die casting ultrathin-walled components

With the rapid development of 3C industries,the demand for high-thermal-conductivity magnesium alloys with high mechanical performance is increasing quickly.However,the thermal conductivities of most common Mg foundry alloys(such as Mg-9wt%-1wt%Zn)are still relatively low.In this study,we developed a high-thermal-conductivity Mg-4Al-4Zn-4RE-1Ca(wt%,AZEX4441)alloy with good mechanical properties for ultrathin-walled cellphone components via high-pressure die casting(HPDC).The HPDC AZEX4441 alloy exhibited a fine homogeneous microstructure(average grain size of 2.8μm)with granular Al_(11)RE_(3),fibrous Al_(2)REZn_(2),and networked Ca_(6)Mg_(2)Zn_(3) phases distributed at the grain boundaries.The room-temperature thermal conductivity of the HPDC AZEX4441 alloy was 94.4 W·m^(-1)·K^(-1),which was much higher than 53.7 W·m^(-1)·K^(-1) of the HPDC AZ91D alloy.Al and Zn in the AZEX4441 alloy were largely consumed by the formation of Al_(11)RE_(3),Al_(2)REZn_(2),and Ca_(2)Mg_(6)Zn_(3) phases because of the addition of RE and Ca.Therefore,the lattice distortion induced by solute atoms of the AZEX4441 alloy(0.171%)was much lower than that of the AZ91D alloy(0.441%),which was responsible for the high thermal conductivity of the AZEX4441 alloy.The AZEX4441 alloy exhibited a high yield strength of~185 MPa,an ultimate tensile strength of~233 MPa,and an elongation of~4.2%.This result indicated that the tensile properties were comparable with those of the AZ91D alloy.Therefore,this study contributed to the development of high-performance Mg alloys with a combination of high thermal conductivity,high strength,and good castability.

Mechanism of die soldering during aluminum die casting

Soldering is a unique casting defect associated with die casting or metal mold casting of aluminum alloys. It occurs when molten aluminum sticks or solders the surface of the die steel and remains there after the ejection of the casting, causing a surface defect and dimensional inaccuracy of the castings and increased machine downtime. Soldering occurs easily when a bare die steel mold is used for die casting of aluminum alloys. When molten aluminum comes in contact with the die steel at a temperature higher than a critical temperature, the iron and aluminum atoms diffuse into each other, forming a series of intermetallic phases and a liquid aluminum-rich fcc phase. This liquid phase exists between intermetallic phases. On cooling, the liquid fcc phase solidifi es on the intermetallic phases and grows into the casting, resulting in soldering. The critical temperature is the eutectic temperature near the aluminum corner of the phase diagram. If the die is protected using a nonreactive ceramic coating, soldering starts at locations where local coating failure occurs. Molten aluminum comes into contact with die steel through the coating failure locations and eats into the steel matrix, forming small pits. As these small pits grow, the coating is gradually removed and soldering becomes more severe. Details of die soldering step on a bare steel die and on a coated die material are discussed.

Influences of Casting Pressure Conditions on the Quality and Properties of a Magnesium Cylinder Head Cover Die Casting

Casting pressure conditions have great influences on the casting defects, such as gas porosity, shrinkage porosity and gas holes. A Mg cylinder head cover die casting was used to experimentally study the influences of casting pressure, the loading time and the piston position of pressure intensification on the variation of pressure and the quality of casting. The results show that casting pressure, the loading time and the piston position of pressure intensification have great influences on the pressure variations in the mold, the quality and performance of casting. The external quality, the density and the tensile strength of casting were improved with the increase of casting pressure and the piston position of pressure intensification and the decrease of the loading time of pressure intensification.

A study on joining magnesium alloy high pressure die casting components with thread forming fasteners

With tremendous weight saving potential,magnesium alloy high pressure die casting components have been widely used for automotive applications.Magnesium fastening technology is thus becoming increasingly important to design engineers.Joining as-cast holes of magnesium high pressure die casting components with thread forming fasteners provides significant advantages for the assembly process,overall cost benefit and joint integrity.This type of joint is thus preferred for structural applications.Designing the thread forming fasteners with as-cast holes follows the general rules for designing for the machined holes,including carefully designing the variables such as the assembly torque range,the length of thread engagement,the hole diameter and required failure mode.In addition,special attention needs to be paid to the draft angles of the magnesium cast components that are required for the die casting process.In this paper,the effects of above key factors,individually and combined,on the joint performance of thread forming fasteners with as-cast blind holes of AM60B magnesium components are studied.A joint design philosophy was proposed to optimize both joint performance(the prevailing torque,the failure torque and the failure mode)and manufacturing easiness(the hole diameter and corresponding draft angle).The detailed design considerations for as-cast holes of magnesium HPDC are discussed and explained through a hypothetical example.

Effects of particle size,bimodality and heat treatment on mechanical properties of pumice reinforced aluminum syntactic foams produced by cold chamber die casting

In recent years,metal matrix syntactic foams(MMSFs)have become highly attractive owing to their unique physical,microstructural and mechanical features.Due to their promising potential for different industrial areas like automotive,aviation,and defense,these advanced engineering materials can also be evaluated as serious alternatives to particle reinforced metallic composites and conventional metallic foams.Differently from previously reported laboratory scaled techniques in the literature,this experimental effort focuses on the feasibility of MMSF manufacturing via a fully automated and industrial-based cold chamber die casting technique.Accordingly,1-2 mm,2-4 mm,and bimodal(50vol.%)natural-based pumice filled aluminum syntactic foams were manufactured utilizing a purpose-made casting machine.Physical,macroscopic,and microscopic examinations show that all of the fabricated samples display perfect matrix/filler harmony.Average density levels of fabricated syntactic foams range between 1.50 and 1.80 g·cm^(-3) depending upon the pumice particles size interval.To assess mechanical responses,quasi-static compression tests were performed.Furthermore,half of the foam samples were subjected to heat treatment to explore possible influences of aging on the compressive features and damage modes.Results indicate that although the heat treatment enhances the compressive strength,plateau stress,and energy absorption properties of the fabricated foams,it changes damage mode of the samples by causing brittle dominant deformation.

Defect band formation in high pressure die casting AE44 magnesium alloy

The characteristics of defect bands in the microstructure of high pressure die casting(HPDC)AE44 magnesium alloy were investigated.Special attention was paid to the effects of process parameters during the HPDC process and casting structure on the distribution of defect bands.Results show that the defect bands are solute segregation bands with the enrichment of Al,Ce and La elements,which are basically in the form of Al_(11)RE_(3) phase.There is no obvious aggregation of porosities in the defect bands.The width of the inner defect band is 4-8 times larger than that of the outer one.The variation trends of the distribution of the inner and outer defect bands are not consistent under different process parameters and at different locations of castings.This is due to the discrepancy between the formation mechanisms of double defect bands.The filling and solidification behavior of the melt near the chilling layer is very complicated,which finally leads to a fluctuation of the width and location of the outer defect band.By affecting the content and aggregation degree of externally solidified crystals(ESCs)in the cross section of die castings,the process parameters and casting structure have a great influence on the distribution of the inner defect band.

Effect of Injection Velocity on Structure Part Characteristic in A50 Die Casting Process with High Vacuum System

When diecasting large and thin Mg alloy parts,material defects occur,which include porosity,nonuniform mechanical properties,irregular surfaces,and incomplete filling.To resolve these problems,it is necessary to have uniform injection velocities and temperatures as well as control the melt.This study investigated the feasibility of producing large and thin components using a die caster by attaching a high vacuum system.In particular,the effects of injection velocity on surface quality and the mechanical properties of the products were investigated.Hence,an injection velocity scheme and a die structure capable of casting in a vacuum were proposed.As a result,it was found that the critical low injection velocity was 0.2 m/s to produce large thin Mg alloy structures having good mechanical properties.