High pressure die casting (DC) is an effective manufacturing method suitable for high accuracy, mass production. However, its high injection speeds produce an unstable molten metal flow that induces ...gas porosity; a critical casting defect that limits the application of heat treatment and welding. In this study, we performed casting using conventional DC(CDC), vacuum assisted DC(VDC), pore-free DC(PFDC), as well as a novel vacuum assisted PFDC(VPFDC). We evaluated the gas porosity of the as-cast and heat-treated specimens using computed tomography, microstructure, and mechanical property analysis. The VDC-, PFDC-, and VPFDC-prepared specimens recorded lower inner gas quantities than that the CDC-prepared specimen; the lowest (4.914 cc/100 g) was recorded for the VPFDC-prepared specimen (product section). X-ray diffraction and optical microscopy analysis showed that the specimens all contained α-Al, eutectic Si, θ-Al2Cu, and Al2O3. However, scanning electron microscopy, transmission electron microscopy, and energy dispersive spectroscopy analysis indicated a higher oxygen content in the PFDC-prepared specimen than the CDC-prepared specimen. Moreover, the tensile properties of the VDC-, PFDC-, and VPFDC-prepared specimens were better than those of the CDC-prepared specimens, and after heat treatment, the tensile properties of the CDC-prepared specimen deteriorated while those of the VDC-, PFDC-, and VPFDC-prepared specimens improved.
•Properties comparison of specimens cast using different casting processes.•Vacuum assisted pore-free die casting process minimizes gas porosity of specimens.•Pore-free die casting produces specimens with higher oxygen content.•Heat treatment improves vacuum-assisted pore-free die cast–parts’ tensile strength.•Evaluation of a novel vacuum-assisted pore-free die casting process.
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Two-stage super vacuum (19 mbar) assisted high pressure die casting (HPDC) was achieved by evacuating from the die cavity and the shot sleeve simultaneously. The effect of super ...vacuum assisted HPDC on the repeatability of the tensile properties of Al-Si-Mg-Mn die-cast alloy was investigated in comparison with conventional HPDC. The quantitative Weibull analysis confirmed that super vacuum assisted HPDC improved the repeatability of the tensile properties of the alloy. The data and deviation analysis verified that super vacuum assisted HPDC considerably decreased the fluctuations of the ductility of the alloy by 71% in as-cast state and 84% after solution and ageing treatment. The results also showed that super vacuum assisted HPDC improved the ultimate tensile strength and ductility of the as-cast alloy by 5.6% and 43%, respectively, and increased the ductility of the alloy by 21% after solution and ageing treatment. The significant improvements of ductility and the repeatability of tensile properties were originated from the decrease of porosity volume fraction and porosity size in the alloy processed by super vacuum assisted HPDC. The reduction of defect size can improve the stress distribution and retard the crack initiation in castings. Therefore, the tensile strength and ductility were enhanced in the die-cast alloy processed by super vacuum assisted HPDC.
Additive manufacturing is a good alternative to conventional methods for the production of near net shape geometries with high geometric complexity shorter lead times, being a good option for the ...manufacturing of dies for die casting process. In this research, a novel hot-work tool steel for aluminum die casting applications manufactured by laser powder bed fusion was investigated. As-built and stress-relieved (AS-B + SR) state was established and used as the reference condition, and subsequent post-treatments were added and compared to the reference condition. Test parts were evaluated using tensile, impact, hardness and thermal fatigue testing. Compared to the reference condition, heat treatment (HT), significantly increased the hardness, yield and ultimate tensile strengths of the material, due to the obtained tempered martensite microstructure. Hot isostatic pressing (HIP) prior to HT significantly increased the impact toughness and ductility, and slightly increased the yield and ultimate tensile strength values compared to the HT condition. The addition of nitriding treatment after HT, without intermedium HIP step, resulted in the highest surface hardness and lowest impact toughness. Thermal fatigue was mostly affected by the hardness and the softening of the material during the thermal fatigue testing. Results showed that a high surface hardness resulted in a higher thermal fatigue crack nucleation, meanwhile conditions with a high softening during thermal fatigue performance resulted in a higher crack propagation.
A series of Al-xCe (x = 2, 4, 6, 8, 10 wt%) and Al–8Ce-yMg (y = 0, 0.10, 0.25, 0.50, 0.75 wt%) alloys were prepared by high-pressure die casting. The introduced cerium element promoted the nucleation ...of α-Al grains. Al11Ce3 phase served as the heterogeneous nucleation substrate of α-Al due to the small lattice mismatch of 6.72%. According to the results calculated by Nelson-Riley extrapolation function, the lattice constant of α-Al increased from 4.0511 Å to 4.0540 Å with the increasing of Mg content from 0 wt% to 0.75 wt%. Due to the solid solution strengthening effect of Mg atoms, the yield strength of Al–8Ce-yMg alloys and the hardness of α-Al matrix in the Al–8Ce-yMg alloys showed a parabolically increasing tendency, from 92 MPa to 115 MPa and 0.502 GPa–0.575 GPa, respectively. The work hardening capacity of Al–8Ce-yMg alloys was improved by the solid solution of Mg with the work hardening exponent increasing from 0.21 to 0.27. The solid solution of Mg atoms reduced the stacking fault energy of Al–8Ce-yMg alloys and suppressed the dynamic recovery process of the alloys during deformation process, which promoted the formation of dislocation tangles and dislocation networks in the α-Al matrix.
•Al11Ce3 could act as the heterogeneous nucleation substrate of α-Al due to the small lattice mismatch of 6.72%.•The lattice constant of α-Al increases from 4.0511 Å to 4.0540 Å due to the solid solution Mg atoms.•Solid solution strengthening of Mg improves the yield strength of Al–8Ce-yMg alloys and the hardness of α-Al matrix.•Solid solution of Mg reduces the stacking fault energy and suppresses the dynamic recovery process of Al–8Ce-yMg alloys.
A high strength (Yield strength ≥ 320 MPa) and high ductility (Tensile elongation ≥ 10%) die–cast aluminium alloy was first developed. The AlSiCuMgMn alloy processed by high pressure die casting can ...provide the high yield strength of 321 MPa, the high ultimate tensile strength of 425 MPa and the high ductility of 11.3%, after solution treated at 510 °C for 30 min and aged at 170 °C for 12 h. The alloy demonstrated 150% increase in ductility over the reported most advanced die–cast aluminium alloy, also comparable tensile properties to the 6000 series wrought aluminium alloys but with much lower manufacturing cost. The as–cast microstructure of the alloy mainly contained the primary α1–Al phase solidified in the shot sleeve, the secondary α2–Al phase solidified in the die, the Al–Si eutectic phase and the intermetallic phases Q–Al5Cu2Mg8Si6 and θ–Al2Cu. The intermetallic phases Q and θ were dissolved into the α–Al matrix during solution. Nanoscale precipitates Q′ and θ′ were precipitated from the α–Al matrix for the strengthening of the alloy through ageing treatment. Multiple effects resulted in the high ductility of the alloy.
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•Advanced die–cast Al alloy was developed with high strength and high ductility.•The developed alloy provides YS of 321 MPa, UTS of 425 MPa and ductility of 11.3%.•The developed alloy demonstrates 150% increase in ductility over the current alloys.•The developed alloy demonstrates comparable tensile properties to wrought Al alloys.•The developed alloy demonstrates milestone tensile properties for HPDC industry.
Forming complex geometries using the casting process is a big challenge for bulk metallic glasses (BMGs), because of a lack of time of the window for shaping under the required high cooling rate. In ...this work, we open an approach named the "entire process vacuum high pressure die casting" (EPV-HPDC), which delivers the ability to fill die with molten metal in milliseconds, and create solidification under high pressure. Based on this process, various Zr-based BMGs were prepared by using industrial grade raw material. The results indicate that the EPV-HPDC process is feasible to produce a glassy structure for most Zr-based BMGs, with a size of 3 mm × 10 mm and with a high strength. In addition, it has been found that EPV-HPDC process allows complex industrial BMG parts, some of which are hard to be formed by any other metal processes, to be net shaped precisely. The BMG components prepared by the EVP-HPDC process possess the advantages of dimensional accuracy, efficiency, and cost compared with the ones formed by other methods. The EVP-HPDC process paves the way for the large-scale application of BMGs.
AlSi9Cu3(Fe) aluminum alloy fatigue test specimens were produced by high pressure die casting (HPDC) and vacuum‐assisted die casting (VPDC) techniques. Non‐destructive material tests (NDT) have been ...performed on cast specimens by computed tomography (CT). Uniaxial fatigue tests with two stress ratios of R = −1 and R = 0.1 have been performed in the high cycle fatigue (HCF) regime, and the CT results were reassigned after the fatigue test in order to identify the origin of the failure. The aim of this paper is to establish a relationship between the CT result and fatigue failure of die cast specimens. The location and the size of the casting defect determine the specimen fatigue life. It has also been found that the fatigue life is determined not only by the size of the defect but also by its location with respect to the position of the highly stressed area. The results can be used to judge the applicability of cast parts after non‐destructive testing.
Microstructure and mechanical properties of a newly developed Al–4Mg–2Fe alloy prepared via high pressure die casting (HPDC) were studied. Attention was focused on the characteristics of the ...iron-rich intermetallic compounds (IMCs) and their influence on crack initiation and propagation. Result shows three types of iron-rich IMCs (Al13Fe4) existed in the alloy. The first is the primary iron-rich IMCs (P-IMCs) precipitating prior to the α-Al phase. These IMCs comprised external solidified iron-rich IMCs (P-IMC)I forming inside the shot sleeve and secondary iron-rich IMCs (P-IMCs)II inside the cavity. The second is fine ternary eutectic iron-rich IMCs (TE-IMCs), one of the phases of the ternary Al–Al8Mg5–Al13Fe4 eutectic. The third is binary eutectic iron-rich IMCs (BE-IMCs), which formed between P-IMCs and TE-IMCs via binary eutectic reaction: L→Al + Al13Fe4. Accordingly, the (P-IMCs)I acted as crack initiation sources regardless of the orientation due to the extremely large size and aspect ratio. The (P-IMCs)II exhibiting a large aspect ratio but small size accelerated the crack propagation. The BE-IMC and TE-IMCs, due to the tiny small size and aspect ratio, barely exhibited any effect on the final failure.
•Influence of HPDC solidification behavior of AlMg4Fe2 alloy on iron-rich intermetallic compounds (IMCs) was studied.•Three types of iron-rich IMCs were observed, and the corresponding effect on the mechanical properties was discussed.•3-D large size reconfiguration technology was performed to characterize the size and morphology of iron-rich IMCs.•The influence of iron-rich IMCs on crack behavior was dependent on the size and morphology regardless of orientation.
The characterization of externally solidified crystals (ESCs) and porosities in a high-pressure die-cast AlSi10MnMg alloy was investigated using optical microscope (OM) and computed tomography (CT) ...with particular attention on the effect of shot speeds on the ESCs and fracture behavior. Results showed that ESCs tended to agglomerate at the center region and changed from fine globular grains into large size dendrites from surface to center. The formation of the ESCs is found to be coarser as the "slow shot speed" in the first stage of high-pressure die casting (HPDC) or the "fast shot speed" in the second stage of HPDC is reduced, consequently, the corresponding ESC area fraction increased. From the fractured morphology, the plate specimen with a higher ESC content exhibited a rough fracture and a large volume fraction of shrinkage porosities was discovered beneath the fracture surface especially when a lower fast shot speed was applied. In in-situ tensile test, the large size shrinkage porosity served as a crack source and it further expanded in an inter-granular mode along ESC boundaries/other porosities (which caused a tortuous crack route) or in a trans-granular mode across the ESC grains/fine (α-Al)II grains (which caused a flat crack route). In addition, the gas porosities in the specimen promoted the crack propagation as a crack concentration area and experienced almost no deformation during the tensile process.
The low-pressure die casting (LPDC) process was experimentally and numerically studied to produce AlSi7Mg0.3 components such as steering knuckles. Steering knuckles are important safety components in ...the context of a vehicle’s suspension system, serving as the mechanical interface that facilitates the articulation of the steering to control the front wheel’s orientation, while simultaneously bearing the vertical load imposed by the vehicle’s weight. This work focuses on the development of a numerical model in ProCAST®, replicating the production of the aforementioned part. The model analyses parameters such as the filling dynamics, solidification process, and presence of shrinkage porosities. For the purpose of evaluating the quality of the castings, six parts were produced and characterised, both mechanically (tensile and hardness tests) and microstructurally (porosity and optical microscopy analysis). When correlating simulation results with the available experimental data, it is possible to conclude that the usage of the LPDC process is a viable alternative to the use of steels and other metals for the production of very high-quality castings while using lighter alloys such as aluminium and magnesium in more demanding applications.
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