High Pressure Die Casting Research Articles

Microstructure and impact behavior of Mg-4Al-5RE-xGd cast magnesium alloys

This work investigated the microstructure and impact behavior of Mg-4Al-5RE-xGd (RE represents La-Ce mischmetal; x = 0, 0.2, 0.7 wt.%) alloys cast by high-pressure die casting (HPDC), permanent mold casting (PMC), and sand casting (SC) techniques. The results indicated that with increasing Gd content, the grain sizes of the HPDC alloy had a slight change, but the grains of the PMC and SC alloys were significantly refined. Besides, the acicular Al11RE3 phase was modified into the short-rod shape under the three casting conditions. The impact toughness of the studied alloy was mainly dominated by the absorbed energy during the crack initiation. With increasing Gd content, the impact toughness of the studied alloy monotonically increased due to the lower tendency of the modified second phase toward crack initiation. The impact stress was higher than the tensile stress, exhibiting a strain rate sensitivity for the mechanical response; however, the HPDC alloy had an inconsistent strain rate sensitivity during the impact event due to the transformation of the deformation mechanism from twinning to slip with increasing strain. Abundant dimples covered the fracture surface of the fine-grained HPDC alloys, indicating a typical ductile fracture. Nevertheless, due to the deficient {101¯2} twinning activity and the suppressed grain boundary sliding during the impact event, the HPDC alloys showed insufficient plastic deformation capacity.

A Mg-6Y-3Zn-1Al Mg HPDC alloy having high thermal stability: Study of grain growth kinetics

The thermal stability and grain growth kinetics of a high-pressure die casting (HPDC) Mg-6Y–3Zn-1Al (WZA631, wt%) alloy with long-period stacking ordered (LPSO) phase is studied by subsequent annealing at different temperatures and time. The grain size of the as-cast and annealed samples is determined using the linear intercept method. It is found that grain size of WZA631 alloy hardly changes up to 450 °C, indicating the microstructure is thermally stable. The grain growth kinetics of WZA631 alloy between 450 °C and 550 °C is well described by the kinetic equation, Dn−D0n=kt. The grain growth exponent varies with temperature, ranging from n = 4.98 at 450 °C to n = 1.45 at 550 °C. The values of activation energy Eg are approximately 122.5 kJ/mol and 139.1 kJ/mol, respectively, for annealing temperature below and above 500 °C, which identifies the bulk diffusion to be the principal grain growth mechanism in the studied temperature range. The growth rate constant k at 450–500 °C is around 2–4 orders lower than other typical Mg alloys, suggesting the excellent thermal stability below 500 °C. The grain coarsening temperature TGC and softening temperature TS are all around 500 °C, implying the critical temperature related to the thermal stability of WZA631 alloy is ~500 °C. The microstructure evolution shows that LPSO network structure is a predominant factor inhibiting the grain growth of HPDC WZA631 alloy, and the dissolution of LPSO results in the variation of grain growth exponent.

Combined Probabilistic Approach and Stress State Dependency on the Failure Modeling of HPDC Aural-2 Alloy

Both experimental method and numerical method are used to analyze the large variation in the material ductility of high pressure die casting (HPDC) Aural-2 alloy in the present work. The X-ray tomography (XRT) technique is used to characterize and reveal the significant variation of the internal porosity for the investigated material. The Mises plasticity model in conjunction with a mixed Swift-Voce hardening law, and a stress state dependent fracture initiation criterion are used to accurately describe the deformation response of the material. Very good agreement with the experimental results is obtained in the predicted average force-displacement responses for the calibrated stress states. A probabilistic damage mechanics model is put forward to depict the apparent stochastic ductile fracture behavior over a wide range of stress states. The 5th and 95th percentiles of the fracture initiation locus are recalibrated based on the proposed probabilistic ductile fracture model, which could provide an almost perfect prediction of the maximum and minimum bounds of force-displacement curves.

Correlation Among Microstructure, Mechanical Properties, and Thermal Stability of a Novel HPDC Al–12Si Alloy with Minor Sc

The microstructure, mechanical properties, and thermal stability of high-pressure die casting (HPDC) Al–12Si–Sc alloy with 0.1 wt% Sc addition are investigated. Compared with the commercial A380 alloy, the alloy shows a significant refinement of α-Al and eutectic Si microstructure. Meanwhile, β-Fe with irregular morphology shows a smaller size and lower volume fraction in Al–12Si–Sc alloy. Upon as-cast state, the elongation of the alloy is improved to 6.7% with an ultimate tensile strength of 332 MPa, which is a better combination of ductility and strength in the literature. After thermal exposure at 200 °C for 200 h, it retains tensile strength of 277 MPa and holds the microhardness up to 90 HV even exposure for 1000 h. These excellent properties may widen the application of HPDC Al–Si alloy for the cylinder block and cylinder head.

Developing a prescriptive decision support system for shop floor control

PurposeThe reported study aims at connecting the two crucial aspects of manufacturing of future, i.e. advanced analytics and digital simulation, with an objective to facilitate real-time control of manufacturing operations. The work puts forward a framework for designing prescriptive decision support system for a multi-machine manufacturing environment.Design/methodology/approachThe schema of the decision support system design begins with the development of a simulation model for a manufacturing shop floor. The developed model facilitates prediction followed by prescription. As a connecting link between prediction and prescription mechanism, heuristics for intervention have been proposed. Sequential design and simulation-based demonstration of activities that span from development of a multi-machine shop floor model; a prediction mechanism and a scheme of intervention that ultimately leads to prescription generation are the highlights of the current work.FindingsThe study reveals that the effect of intervention on the observed predictors varies from one another. For a machine under observation, subject to same intervention scheme, while two of the predictive measures namely penalty and desirability stabilize after a certain point, a third measure, i.e. complexity, shows either an increase or decrease in percent change. The work objectively establishes that intervention plans have to be evaluated for every machine as well as for every environmental variable and emphasizes the need for dynamic evaluation and control mechanism.Originality/valueThe proposed prescriptive control mechanism has been demonstrated through a case of a high pressure die casting (HPDC) manufacturer.

On the deformation behavior of heterogeneous microstructure and its effect on the mechanical properties of die cast AZ91D magnesium alloy

Both a conventional flow distributer and an improved one with a flow buffer were applied respectively during the high pressure die casting (HPDC) process, and samples of AZ91D magnesium alloy with different microstructure mainly consisting of α-Mg grains, β-phase and porosities were obtained. According to the grain orientation analysis, the predominant deformation behavior in α-Mg grains was dislocation slip, supplemented by deformation twinning. Dislocation slip was more difficult to occur in the samples with the improved flow distributer on account of the fact that the size of α-Mg grains in the microstructure was finer and more uniform. During the in situ tensile deformation test, cracks were observed to initiate from gas-shrinkage pore and island-shrinkage, and two main crack propagation mechanisms, porosity growth and coalescence were found accordingly. When the crack was in contact with the β-phase, it would pass through and fracture the network β-phase, whereas bypass the island β-phase by detaching it from the surrounding α-Mg grains. Mechanical property tests showed that the samples with relatively more homogeneous microstructure would perform higher mechanical properties, which was the combined effect of matrix α-Mg grains, β-phase, and porosities.

Production of Aluminum Alloy Sealing Part by Semi Solid Die Casting Method

High Pressure Die Casting (HPDC) is a widely preferred process for the production of non-ferrous metals with low melting temperatures. It is particularly suitable for close-to-finish and high-volume production of relatively complex shaped parts. Aluminum-Silicon-Copper alloys, which are frequently preferred in this method, find themselves in many sectors ranging from automotive to aviation. With the developing technology, the usage of High Pressure Die Casting technology has increased significantly, produced part types and the number of parts produced on an annual basis has reached remarkable amounts with the shortening of cycle times. In this study, a supra-eutectic silicon valued Aluminum-Silicon-Copper alloy was produced by gas-induced semi-solid die casting method using a cold chamber high pressure die casting machine. The study observed that many casting problems, especially shrinkage gaps and gas porosity, were overcome, while the microstructure of the parts on which the gas induced semi-solid die casting method was applied was preserved. In addition, energy saving is achieved by lowering the temperature of the holding pot, and thermal fatigue cracks that will occur in the mold in the long-term depending on the temperature difference will be delayed and the mold life will increase.

A high performance Mg–Al–Ca alloy processed by high pressure die casting: Microstructure, mechanical properties and thermal conductivity

The demand for high-performance magnesium alloys, including high strength, high thermal conductivity, and good heat resistance, is growing rapidly in practical applications. Here, we report a high performance Mg–7Al–3Ca (AX73, wt.%) alloy with high strength, good thermal conductivity, and acceptable heat resistance via the high-pressure die casting (HPDC) method. Compared to the commonly used Mg–4Al–4RE (AE44) and Mg–9Al–1Zn–0.25Mn (AZ91D), the HPDC AX73 exhibited a much higher yield strength (YS) at room temperature (RT) and 175 °C. The high YS was attributed to the combinations of fine-grain strengthening, second phase strengthening from numerous Al2Ca eutectic phases, and solid solution strengthening from Al solutes. After the aging treatment, the room-temperature YS of AX73 alloy was further improved from 184 MPa to 196 MPa due to fine Al2Ca precipitation. Since the existence of Ca obviously reduced the Al solutes in the α-Mg matrix, the AX73 and AX73 aged alloys possessed reasonable thermal conductivity of 67 and 68.5 W(m·K)−1, respectively.

Solidification behavior and enhanced properties of semi-solid Al–8Si–0.5Fe alloys fabricated by rheo-diecasting

Compared with the high pressure diecasting, rheo-diecasting has an advantage in decreasing defects, refining microstructure and improving properties. In the present work, an Al–8Si–0.5Fe alloy with a good combination of mechanical property and thermal conductivity was obtained by rheo-diecasting. The solidification behavior, mechanical properties, and thermal conductivity of the alloy under rheo-diecasting were discussed. The results demonstrated that the chilling effect and shearing vibration not only affected the primary solidification on the vibrating contraction sloping plate, but also the secondary solidification in the remaining liquid during rheo-diecasting. The rheo-diecasting alloy possessed spherical primary α1-Al grains and secondary α2-Al grains, small-sized Al5FeSi phases, eutectic Si phases, and low porosities, and thus exhibited the high mechanical properties and thermal conductivity. With decreasing pouring temperature from 690 °C to 670 °C, the size of primary α1-Al grains, secondary α2-Al grains, Al5FeSi phases and eutectic Si phases was decreased due to high cooling rate, which further improved the mechanical properties and thermal conductivity of the alloy.

Microstructure-property relationships in HPDC Aural-2 alloy: Experimental and CP modeling approaches

Al–Si alloys fabricated by high-pressure die casting (HPDC) have a broad range of applications. Tailored microstructures of HPDC Al–Si alloy were continuously put forward to fulfill the increasing demand for mechanical performance of components. This paper attempts to build microstructure-property relationships of high-pressure die-casting Al–Si alloy to fulfill the increasing demand for mechanical performance of components by tailoring initial microstructure. Moreover, develop a scale-bridging approach to quantitatively upscale the damage initiation of Al–Si alloy under various stress states from micro to macro scale. Both finite element (FE) simulations and Fast Fourier transform (FFT) simulations were applied to calibrate the crystal plasticity parameters. Stress-strain curves simulated by representative volume elements subjected to periodic boundary conditions were validated with the experimental results from uniaxial tensile tests. The response surface design method was herein adopted to rationally and systematically reveal the impact of microstructural heterogeneity on mechanical properties. Finally, damage initiation curves of porous RVEs with distinct characteristics are acquired in terms of the definition of microstructural inhomogeneity criterion. In conclusion, simulation results suggested that strength-related properties are more relevant to the silicon phase characteristics, whereas strain localizations within RVE are observed in the vicinity of pore phase. Furthermore, the predicted failure displacement indicates a good agreement with the experimental results of macro tensile tests. The damage initiation strain shows significant dependence on the stress states and pore phase features (size, volume fraction and morphology).

Characteristics and formation mechanisms of defect bands in vacuum-assisted high-pressure die casting AE44 alloy

The microstructure in vacuum-assisted high-pressure die casting (HPDC) Mg-4Al-4RE (AE44) alloy was studied. Special attention was paid to the characteristics of defect bands and their formation mechanisms. Since double defect bands are commonly observed, the cross section of die cast samples is divided into five parts with different grain morphologies and size distributions. The inner defect band is much wider than the outer one. Both the defect bands are solute segregation bands, resulting in a higher area fraction of Al11RE3 phase than that in the adjacent regions. No obvious aggregation of porosities is observed in the defect bands of AE44 alloy. This may be due to a narrow solidification temperature range of AE44 alloy and a large amount of latent heat released during the precipitation of intermetallic phases. The formation of the defect bands is related to the shear stress acting upon the partially solidified alloy, which can lead to collapse of the grain network. However, the generation mechanisms of shear stress in the outer and inner defect bands are quite different.

An a Priori Discussion of the Fill Front Stability in Semisolid Casting

Metal casting is an industrially important manufacturing process offering a superior combination of design flexibility, productivity and cost-effectiveness, but has limitations due to filling related defects. Several semisolid casting processes are available capable of casting at a range of solid fractions to overcome this. The current communication aims to review the filling front behaviour and give a new perspective to the gate design in semisolid processing compared to conventional high-pressure die-casting. It is shown that solid fraction and gate widths are critical to avoid instability and spraying.

The effect of different high pressure die casting parameters on 3D microstructure and mechanical properties of AE44 magnesium alloy

To understand the relationship between the process-microstructure-mechanical properties of the high-pressure die-casting (HPDC) AE44 magnesium alloy, 3D reconstruction and 2D characterization were carried out on the HPDC castings produced with different process parameters (low slow-shot speed, fast slow-shot speed, solidification pressure). Microstructural characterization revealed that the formation of shrinkage pores are closely related to ESCs, which were mainly controlled by the low slow-shot speed in shot sleeve (ESCs growth time) and fast slow-shot speed into the die cavity (distribution of ESCs). In addition, solidification pressure can significantly reduce the shrinkage porosity in the center by improving the feeding capacity of liquid metal. Tensile fracture revealed that the tearing ridge is mainly evolved from the slip band of ESCs. The quantity and distribution of ESCs determine the fracture mode of castings. The relationship between mechanical properties of castings and the morphology of ESCs and porosity is also statistically discussed.

Manufacturing of Aluminum Matrix Composites Reinforced with Carbon Fiber Fabrics by High Pressure Die Casting.

Aluminum matrix composites reinforced with carbon fiber have been manufactured for the first time by infiltrating an A413 aluminum alloy in carbon fiber woven using high-pressure die casting (HPDC). Composites were manufactured with unidirectional carbon fibers and with 2 × 2 twill carbon wovens. The HPDC allowed full wetting of the carbon fibers and the infiltration of the aluminum alloy in the fibers meshes using aluminum at 680 °C. There was no discontinuity at the carbon fiber-matrix interface, and porosity was kept below 0.1%. There was no degradation of the carbon fibers by their reaction with molten aluminum, and a refinement of the microstructure in the vicinity of the carbon fibers was observed due to the heat dissipation effect of the carbon fiber during manufacturing. The mechanical properties of the composite materials showed a 10% increase in Young’s modulus, a 10% increase in yield strength, and a 25% increase in tensile strength, which are caused by the load transfer from the alloy to the carbon fibers. There was also a 70% increase in elongation for the unidirectionally reinforced samples because of the finer microstructure and the load transfer to the fibers, allowing the formation of larger voids in the matrix before breaking. The comparison with different mechanical models proves that there was an effective load transference from the matrix to the fibers.

Influence of Process Parameters on Filling and Feeding Capacity during High-Pressure Die-Casting Process

The quality of high-pressure die casting (HPDC) is largely determined by the process parameters. The objective is to study the influence of process parameters on melt filling and feeding capacity. The research is carried out by means of numerical simulations and orthogonal experiments. The results show that the influence of process parameters is different. The piston velocity of the fast stage has the most obvious impact. As the piston velocity of the fast stage increases, the filling capacity and feeding capacity also increase. The melt injection temperature should not be too low; otherwise, it would be easy to cause gas porosity. The piston velocity of the slow stage should not be too high; otherwise, it would cause air entrainment. The influence of the pressure maintaining time is not obvious due to the ingate solidifying prematurely. The recommended process parameters are a melt injection temperature of 660–680 °C, a piston velocity of 0.1–0.2 m/s in the slow stage, and a piston velocity 2.4–3.2 m/s in the fast stage. This also suggests that appropriate technology should be adopted to delay the solidification time of the ingate in order to realize the feeding effect of pressurization.

Measuring and Modeling Microsegregation in High-Pressure Die Cast Mg–Al Alloys

Measuring and Modeling Microsegregation in High-Pressure Die Cast Mg–Al Alloys

Microstructure-refinement–driven enhanced tensile properties of high-pressure die-cast A380 alloy through friction stir processing

This work employs friction stir processing (FSP), a well-known severe plastic deformation technique, to selectively modify the microstructure of thin-walled, high-pressure die-cast (HPDC) aluminum alloy A380, a major HPDC alloy fabricated in the die casting sector. FSP effectively breaks down Al dendrites and acicular Si particles, creating a homogenized distribution of equiaxed Si particles in the aluminum matrix. After FSP, the refined Si particles (~1.5 μm) are smaller than the eutectic Si particles (3–8 μm) in HPDC condition. In addition, interparticle distance has decreased almost 50% compared to dendritic arm spacing, and FSP has reduced the aspect ratio of Si particles to ~2. Furthermore, FSP eliminates porosity, and breaks down needle-like second-phase Fe-Mn and Cu-rich particles, yielding a refined, homogeneous distribution. The FSP-induced microstructural refinement and porosity reduction improve bulk yield strength and ductility by 23% and 66%. Tensile properties are enhanced beyond those of the die skin of the HPDC plate, and the alloy possesses lower defect density and a highly refined microstructure. This study establishes the viability of FSP as a tool for microstructure modification and mechanical property improvement for HPDC Al alloys for the light-weighting goal of the automotive industries.

Investigation on microstructure heterogeneity of the HPDC AlSiMgMnCu alloy through 3D electron microscopy

The microstructural characteristics of the high pressure die casting (HPDC) AlSiMgMnCu alloys in the skin layer, segregation band and the central zone were investigated in three dimensions by serial block-face scanning electron microscopy (SBFSEM). The results present that the volume fractions of α-Al15(Fe, Mn)3Si (α-Fe phase), β-Mg2Si (β phase) and Q-Al5Cu2Mg8Si6 (Q phase) in the skin layer and the central zone are higher than those in the segregation band zone. The volume fractions and sizes of the θ-Al2Cu phase (θ phase) in the skin layer and the central zone are lower than those in the segregation band zone. In the skin layer, the preferential growth orientation of the α-Fe phase with plate-like morphology is parallel to the heat transfer direction, while the other phases exhibit a complex seaweed-like morphology. In the central zone and the segregation band zone, the shearing stress and turbulent flow during the filling process lead to the morphology of α-Fe and β-Mg2Si relatively regular. However, the morphology of Q-Al5Cu2Mg8Si6 and θ-Al2Cu phases are irregular owing to their lower solidification temperatures. The distribution and morphology of β-Mg2Si, Q-Al5Cu2Mg8Si6 and θ-Al2Cu in the segregation band zone mainly determined the distribution and morphology of the α-Fe phase.

Padded Self-Piercing Riveting (P-SPR) on Magnesium High Pressure Die Casting

<div class="section abstract"><div class="htmlview paragraph">Padded self-piercing riveting (P-SPR) is a newly developed multi-material joining technology to enable less ductile materials to be joined by self-piercing riveting (SPR) without cracking. A deformable and disposable pad was employed to reduce the stress distribution on the bottom surface by supporting the whole bottom sheet continuously during rivet setting process. To verify the P-SPR process, 2.0mm thick 6061-T6 wrought aluminum was joined with 3.2mm thick coated AM60B magnesium high pressure die casting (HPDC) by using 1.0mm thick dual-phase 600 (DP600) steel as the pad. Regular SPR processes with 2 different die geometries were studied as a comparison. Compared to the regular SPR processes, P-SPR demonstrated advantages on coating protection, crack mitigation and joint strength.</div></div>

Corrosion Behavior of Gravity Cast and High-Pressure Die-Cast AM60 Mg Alloys with Ca and Y Addition

In this study, the microstructure and related corrosion behavior of AM60 alloys with/without Ca and Y addition upon gravity casting (GC) and high-pressure die-casting (HPDC) are investigated by means of SEM/EDS characterization, immersion/salt spray test, hydrogen releasing, as well as electrochemistry examination. When utilizing GC, AM60 alloy with Ca and Y addition (named AZXW6000 alloy) has better corrosion resistance compared with AM60 alloy. Thanks to grain refinement and second phase networks introduced in HPDC, the anti-corrosion properties of the AM alloy seem much better than those of the GC counterpart. The corrosion mechanism of both GCed and HPDCed AM60-based alloys is also investigated in detail. The inspiration from present work can provide more thinking for developing high corrosion-resistant Mg alloys using different casting methods.