High-pressure Die-cast Alloy Research Articles

Characteristics and distribution of microstructures in high pressure die cast alloys with X-ray microtomography: A review

Characteristics and distribution of microstructures in high pressure die cast alloys with X-ray microtomography: A review

Cyclic deformation behavior of an overaged high-pressure die-cast aluminum alloy

The aim of this study is to identify the deformation behavior of a high-pressure die-cast Silafont®-36 aluminum alloy in an overaged T7 condition in relation to the significant microstructural changes caused by the overaging heat treatment. The T7 aluminum alloy exhibited a distinctive composite-like microstructure, consisting of coarser α-Al grains and larger spherical Si particles embedded in the matrix, in contrast to its as-cast and T4 counterparts. The softer α-Al matrix of the T7 alloy as revealed by the nanohardness and microhardness led to improved ductility and longer strain-controlled fatigue life at higher strain amplitudes, despite the lower strength. Cyclic stabilization was observed to be a salient feature of the T7 alloy, stemming from the equilibrium between cyclic hardening and cyclic softening. Strain-energy density-based model, by incorporating a material parameter called ‘intrinsic fatigue toughness’, could be used to predict the fatigue life of the alloy.

Comparing microstructure and mechanical properties of AlSi10 alloy produced by powder bed fusion-laser beam and high pressure die casting

PurposePowder bed fusion-laser beam (PBF-LB) is a rapidly growing manufacturing technology for producing Al-Si alloys. This technology can be used to produce high-pressure die-casting (HPDC) prototypes. The purpose of this paper is to understand the similarities and differences in the microstructures and properties of PBF-LB and HPDC alloys.Design/methodology/approachPBF-LB AlSi10Mg and HPDC AlSi10Mn plates with different thicknesses were manufactured. Iso-thermal heat treatment was conducted on PBF-LB bending plates. A detailed meso-micro-nanostructure analysis was performed. Tensile, bending and microhardness tests were conducted on both alloys.FindingsThe PBF-LB skin was highly textured and softer than its core, opposite to what is observed in the HPDC alloy. Increasing sample thickness increased the bulk strength for the PBF-LB alloy, contrasting with the decrease for the HPDC alloy. In addition, the tolerance to fracture initiation during bending deformation is greater for the HPDC material, probably due to its stronger skin region.Practical implicationsThis knowledge is crucial to understand how geometry of parts may affect the properties of PBF-LB components. In particular, understanding the role of geometry is important when using PBF-LB as a HPDC prototype.Originality/valueThis is the first comprehensive meso-micro-nanostructure comparison of both PBF-LB and HPDC alloys from the millimetre to nanometre scale reported to date that also considers variations in the skin versus core microstructure and mechanical properties.

The aging-hardening behavior of short-time in high pressure die casting AlSi9MgMnZn alloy

Short-time aging is an effective industrial technique for enhancing the mechanical properties of high pressure die cast (HPDC) aluminum alloy components. However, the evolution of precipitation behavior during short-time aging of HPDC alloys remains unclear. In this study, the short-time aging behavior of HPDC AlSi9MgMnZn alloy was investigated. The results show that the AlSi9MgMnZn alloy exhibits effective aging-hardening, with an increment in hardness of approximately 30 HV through the optimal short-time aging treatment (aged at 180 °C for 120 minutes). Higher aging temperatures led to reduced peak hardness and rapid over-aging above 220 °C. The microstructure observation indicates that the peak short-time aging promotes the simultaneous precipitation of β″ precipitates, GP zones and nano Si phases. The contribution of different strengthening mechanisms to hardness was estimated, implying that the coexistence of β″ precipitates and GP zones can provide a positive contribution to aging-hardening during short-time aging. Moreover, as the aging temperature increases, the appearance of β′ precipitates reduces the strengthening effect, leading to a decrease in hardness.

Rotating bending fatigue behavior of high-pressure diecast AlSi10MgMn alloy based on T5 heat treatment parameters

Abstract The study investigates fatigue failure, a common phenomenon in machine elements subjected to cyclic stresses. The analysis emphasizes that the actual stress experienced by materials often falls below their tensile and yield strengths due to repetitive variable stresses, leading to fatigue damage. Fatigue life is measured by the number of cycles endured before failure. This paper focuses on the aluminum alloy of AlSi10MgMn, extensively used in manufacturing due to its strength, low density, and corrosion resistance. Experimental procedures encompassed tensile testing, microstructural examination, SEM analysis, and fatigue testing. Tensile tests provided initial stress values for fatigue testing. Microstructure analyses verified that heat-treated samples exhibited precipitates. SEM analysis disclosed microstructural characteristics, while fracture surface examinations demonstrated higher fatigue resistance in heat-treated specimens. Hardness measurements were conducted, with heat-treated samples showing higher values. Theoretical calculations based on stress and cycle numbers were compared to experimental fatigue results. The derived equations aligned well with the tests. Ultimately, the study underlines the importance of heat treatment on material behavior and fatigue resistance, shedding light on alloy performance and durability enhancement.

Friction stir processing on a strontium modified, thin-wall, vacuum-assisted high-pressure die-cast Aural-5 alloy to improve tensile and fatigue performance

This study explores the application of friction stir processing (FSP) to enhance the material properties of Sr-modified Aural-5 alloy, with a focus on improved tensile and fatigue properties. Aural-5 is a well-known vacuum-assisted high-pressure die-cast (HPDC) Al–Si7–Mg alloy used in the automotive industry to reduce vehicle weight, enhance fuel efficiency, and lower carbon emissions. This alloy modifies its material chemistry with Sr for fine fibrous networks of eutectic silicon and manganese (Mn) to reduce die soldering. It has significantly less iron (Fe) content resulting in the elimination of detrimental needle-shaped Fe-bearing β-phase intermetallic and improving ductility. The initial microstructure of as-received HPDC Aural-5 exhibits shrinkage porosity in the middle section, a dendritic microstructure with fibrous Al–Si eutectic colonies, a shear-band structure beneath the die-wall, large dendritic externally solidified crystals (ESCs), needle-shaped Mg2Si phase and significant second-phase particulates. Some of those microstructural features, such as porosity, ESCs, needle-shaped Mg2Si phase, and large second-phase particles, serve as initiation sites for cracks under mechanical loading, resulting in adverse effects on tensile properties, particularly ductility. FSP effectively transforms the microstructure into a wrought configuration with uniform particle distribution by eliminating porosity and disintegrating dendrites, eutectic colonies, ESCs, second-phase particles, and shear-band structures. FSP-driven microstructure modification enhances yield strength and tensile ductility by ∼30 % and ∼35 %, respectively. The fatigue life of the material in a bending mode configuration (stress ratio R = 0.1) after FSP exhibits enhancements ranging from 2.0 to 3.9 times that of the original HPDC Aural-5 alloy, depending on the applied stress level.

Semi-solid rheo-diecast Mg-xGd-3Y–1Zn-0.4Zr (wt%) alloys and their comparison with conventional HPDC alloys

This work systematically investigated the microstructure and mechanical properties of Mg-xGd-3Y–1Zn-0.4Zr (wt%) alloys prepared via rheo-diecasting (RDC) in comparison to those of conventional high pressure die casting (HPDC) alloys, and revealed their differences in microstructure, casting defects, and mechanical properties. The microstructure of the as-cast RDC Mg-xGd-3Y–1Zn-0.4Zr (wt%) alloys is primarily composed of α-Mg and Mg3(Gd,Y,Zn) eutectic phases. Of the four alloys studied, the GWZ831K and GWZ1431K alloys exhibit the best elongation (EL: 6.4±1.3 %) and the highest strengths (UTS: 270±9 MPa; YS: 201±5.7 MPa), respectively. The GWZ831K alloy exhibits a quasi-cleavage fracture during room-temperature tensile tests, whereas the GWZ1431K alloy demonstrates a brittle fracture. The phase composition of conventional HPDC alloys is fundamentally the same as that of RDC alloys, but their grains and eutectic phases differ in morphology and are smaller in size. Oxide films are frequently found in conventional HPDC castings, but neither oxide films nor pore defects are observed in RDC alloys. Compared to conventional HPDC alloys, RDC alloys have better elongation but lower strength. The lower strength of RDC alloys compared to HPDC alloys can be attributed to larger grains and eutectic phases, along with fewer stacking faults (SFs), resulting in limited strengthening effects of grain boundaries, eutectic second phases and SFs. In contrast, RDC alloys exhibit superior elongation compared to HPDC alloys due to the elimination of oxide films and pore defects, as well as the excellent ductility of the α-Mg matrix that can effectively coordinate deformation.

Research Progress on Thermal Conductivity of High-Pressure Die-Cast Aluminum Alloys

High-pressure die casting (HPDC) has been extensively used to manufacture aluminum alloy heat dissipation components in the fields of vehicles, electronics, and communication. With the increasing demand for HPDC heat dissipation components, the thermal conductivity of die-cast aluminum alloys is paid more attention. In this paper, a comprehensive review of the research progress on the thermal conductivity of HPDC aluminum alloys is provided. First of all, we introduce the general heat transport mechanism in aluminum alloys, including electrical transport and phonon transport. Secondly, we summarize several common die-cast aluminum alloy systems utilized for heat dissipation components, such as an Al–Si alloy system and silicon-free aluminum alloy systems, along with the corresponding composition optimizations for these alloy systems. Thirdly, the effect of processing parameters, which are significant for the HPDC process, on the thermal conductivity of HPDC aluminum alloys is discussed. Moreover, some heat treatment strategies for enhancing the thermal conductivity of die-cast aluminum alloys are briefly discussed. Apart from experimental findings, a range of theoretical models used to calculate the thermal conductivity of die-cast aluminum alloys are also summarized. This review aims to guide the development of new high-thermal-conductivity die-cast aluminum alloys.

A Study of Mg and Ti + Sr Additions to Strengthen Commercial A380 High-Pressure Die Cast Alloy

A Study of Mg and Ti + Sr Additions to Strengthen Commercial A380 High-Pressure Die Cast Alloy

Enhanced toughness and tear resistance of thin-walled High-Pressure Die-Cast aluminum alloys through Friction stir processing

In this study, we investigate the toughness and resistance to tear of thin-wall high-pressure die-cast (HPDC) aluminum alloys in two different orientations following the implementation of friction stir processing (FSP). The FSP technique was applied to two different HPDC Al-Si alloys: the recyclable-grade, high iron, A380 alloy and the premium-quality, low iron, Aural-5 alloy. Our findings reveal significant tear resistance and strength enhancements for both alloys after FSP modification. Specifically, FSPed A380 alloy requires 126% higher energy to tear, and it has 49% higher tear strength than the HPDC counterpart. Similarly, the tear energy and tear strength of the Aural-5 alloy witness enhancements of 69% and 21%, respectively. These findings emphasize the capability of FSP to improve the toughness of HPDC aluminum alloys, creating new possibilities for preventing cracks in a variety of engineering applications.

Microstructure heterogeneity optimization of HPDC Al-Si-Mg-Cu alloys by modifying the characteristic of externally solidified crystals

The microstructure heterogeneity of high pressure die casting (HPDC) Al-8Si-0.5Mg-0.2Cu-2Zn alloy was modified by optimizing the characteristic of externally solidified crystals (ESCs), and their effect on mechanical behavior were also discussed. The results revealed that the formation of microstructure heterogeneity in HPDC alloys was significantly depended on the characteristic of ESCs. In addition, the characteristic of ESCs could be modified by the melt superheat treatment before slow shot process. The morphology of ESCs is dendritic and the distribution show serious segregation at pouring temperature of 685 °C and 725 °C, but evolved to regular and uniformly at pouring temperature of 705 °C. The uniform distribution and regular ESCs leads to uniform stress concentration during tensile deformation at pouring temperature of 705 °C. The cracks mainly initiated at interfacial region of the clustered ESCs, and the obtained yield strength161MPa and ultimate tensile strength 307 MPa, meanwhile, the elongation maintain a high value of 11.4%.

Effect of Al on microstructure and mechanical properties of HPDC Mg-6Y-3Zn alloys

The effect of Al on microstructure and mechanical properties is investigated in novel Mg-6Y-3Zn (WZ63) alloys produced by high-pressure die-casting (HPDC). The morphology of (Al,Zn)2Y phase varies from lamellar to flower-like and then to block shape with 0.4–1.0 wt% Al. The HPDC alloys exhibit fine grain sizes ranging from 4 μm to 7.4 μm, and significant grain refinement is obtained with Al as low as 0.4 wt%, which is different from that in gravity casting. The (Al,Zn)2Y phase is the crack source, and the dimple depth and elongation (EL) reduce with increasing Al content. Still, all the studied HPDC WZ63-xAl alloys maintain excellent tensile properties, keeping 256–274 MPa for tensile strength (UTS) and 7.4–9.7 % EL at room temperature and 188–213 MPa UTS and 10–35 % EL at 250 °C. Optimal mechanical properties are obtained with Al content around 0.4–0.5 wt%.

Analysis of Fractures and Microstructures on Different Injection Speeds in High-Pressure Die-Casting Magnesium Alloy

In this study, to clarify the unknown physical properties of the Mg-Al-Th-RE alloy, the relationship between the injection conditions and the internal porosities, and the mechanical properties exerted by the solidification microstructure was investigated. The obtained cast samples were investigated using X-ray CT internal measurements, tensile tests, Vickers hardness tests, and solidification microstructure observations. The tensile strength and the elongation at the injection speed of 5.0 m/s were higher than at 2.0 m/s. The number of porosities affected the tensile strength and the elongation even at the same fracture position. In addition, it was confirmed that segregation affected the destruction smaller the porosity size and the greater the variability of porosity. As the injection speed increased, the amount of heat transferred between the molten metal and the wall surface also increased, resulting in quick freezing and solidification. The tensile strength increased at the injection speed of 5.0 m/s because the interface between the scattered primary crystals and eutectic systems was narrow. On the other hand, at the injection speed of 2.0 m/s, the tensile strength decreased because the molten metal was delayed in solidification and dendrite growth became remarkable.

Corrosion Behaviour of High-Pressure Die-Cast AZ91 Alloy in NaCl Solution: Effects of Friction Stir Process at High Rotational Speed.

The AZ series of Mg alloys have become promising in several industrial fields thanks to its potential microstructure refinement and the β-Mg17Al12 eutectic that controls the mechanical behaviour. Simultaneously, the rapid degradation characterizing Mg alloys makes the investigation of their corrosion behaviour necessary. The present work considers high-pressure die cast (HPDC) AZ91 alloy to evaluate its corrosion behaviour in 1M NaCl solution and investigates how different friction stir process parameters can affect the corrosion responses. No studies analyse the effects induced by the friction stir processed zone, reached using high rotational speeds (>2000 rpm), on the unprocessed HPDC AZ91 alloy. In addition, the morphological analysis of the corroded surfaces having a friction stir processed zone, in which the grain refinement was not obtained, is not present in the literature yet. Microstructural features were investigated by optical microscope and X-ray diffraction analysis before and after the friction stir process. These were subsequently correlated to the corrosion responses after the immersion tests. The results show that HPDC samples with a very smooth surface have the best corrosion resistance with a corrosion rate lower than 3 mm/year, evaluated through the weight loss, compared to the rougher ones. Both the amount of β-Mg17Al12 eutectic and the wt.% Al in the α-Mg matrix, as well as the surface roughness, influence the corrosion behaviour of friction stir processed samples. The best corrosion resistance was obtained with an HPDC alloy processed at 2500 rpm and 50 mm/min.

The role of the Mg17Al12-phase in the high-pressure die-cast magnesium-aluminum alloy system

The Mg17Al12 β-phase is highly influential to the performance of magnesium-aluminum high-pressure die-casting alloys. Numerous studies have investigated the effect of this phase on the room temperature and elevated-temperature mechanical properties as well as the corrosion, flammability, thermal conductivity and castability performance. This work summarizes the results of these works, as well as the studies that describe control of the Mg17Al12-phase through alloying additions that modify the microstructure and resulting alloy performance. The results of this work can be used as a basis for the development of alloying additions that enable modifications to the performance of high-pressure die-cast magnesium-aluminum-based alloys.

Effect of slow shot speed on externally solidified crystal, porosity and tensile property in a newly developed high-pressure die-cast Al-Si alloy

Effect of slow shot speed on externally solidified crystal, porosity and tensile property in a newly developed high-pressure die-cast Al-Si alloy

A Comparative Study on Microstructure, Mechanical Property, and Electrical Conductivity of Al-7Si-0.6Mg Alloy Produced by High Pressure Die Casting and Semisolid Die Casting

Two casting technologies were introduced to fabricate the Al-7Si-0.6Mg alloy, including high pressure die casting (HPDC) and semi-solid die casting (SSM). The microstructure and mechanical property were studied by optical microscopy (OM), scanning electron microscopy (SEM), X-Ray diffraction (XRD), microhardness and tensile test. The electrical conductivity was also introduced to evaluate the thermal conductivity of the alloys. Results show that the as-cast microstructure of the HPDC alloy and SSM alloy both consists of primary α-Al, eutectic Si and Mg2Si phase. The primary α-Al phase in HPDC alloy possesses fine equiaxed dendrite structure with an average grain size of 29.4 μm. While the SSM alloy forms abundant coarse and globular structure α-Al phase, and the average grain size reaches 98.9 μm. This is because of the lower cooling rate during slurry preparation promotes the formation of a relative coarse microstructure in the SSM alloy. Furthermore, the increased content of eutectic Mg2Si phase was also detected in the SSM alloy. Therefore, the average yield strength and ultimate tensile strength decreases from 148 MPa and 275 MPa of the HPDC alloy to 140 MPa and 254 MPa of the SSM alloy, respectively. However, the elongation and electrical conductivity of the SSM alloy both increases from 5.8±1.3% and 20.0±0.1 MS/m of the HPDC alloy to 7.5±1.2% and 20.6±0.1 MS/m, respectively.

Ductile fracture prediction of HPDC aluminum alloy based on a shear-modified GTN damage model

In this paper, we investigate how the shear-modified Gurson-Tvergaard-Needleman (GTN) model can be used to reveal the effect of manufacturing-process-induced porosity on the scatter of ductile fracture properties of a high-pressure die-casting aluminum alloy. The GTN model exhibits great advantages in predicting the variation of failure strain/displacement by altering the initial void volume fraction (f0), compared with uncoupled ductile damage models. For a specific metallic material, one unique set of model parameters is usually determined from experiments, which leads to the fact that only a deterministic failure strain/displacement can be obtained under a fixed porosity. To overcome this shortcoming of the shear-modified GTN model, a novel parameter calibration scheme is proposed and validated in the present study. Following the physical background of the GTN model, the twelve material parameters of the shear-modified GTN model have been determined based on a combination of macroscopic mechanical tests covering a wide range of stress states and micromechanics-based unit cell simulations. Different from the existing calibration strategies, the simulation results of unit cells embedded with a spherical void have revealed a mutual dependence between the f0 and critical void volume fraction (fc). By conducting interrupted shear tests, the evolution of secondary nucleated void volume fraction was identified according to the statistical results of the fractured brittle silicon particles. The remaining parameters have been further iteratively determined. In the end, the effectiveness of the proposed parameter determination approach is confirmed based on the accurate prediction of stochastic ductile failure properties (both the global failure displacements and the local failure patterns) in different fracture tests. Given the proposed parameters identification strategy, the GTN material models have been enriched to predict the ductile failure behavior of metallic materials, which possess relatively high porosities and more pronounced scattering in failure properties.

The microstructure characteristics and fracture behavior of the polyhedral primary iron-rich phase and plate-shaped eutectic iron-rich phase in a high-pressure die-cast AlSi10MnMg alloy

The characterization of multiple iron-rich phases in high-pressure die-cast AlSi10MnMg alloy was studied. Attention was focused on the formation and fracture behavior of the primary iron-rich phase ((P-IMC)I) formed in the shot sleeve and plate-shaped eutectic iron-rich phase in high-pressure die cast (HPDC) AlSi10MnMg alloy. Results show that multiple types of iron-rich phases with various morphologies, including primary iron-rich phases (polyhedral (P-IMC)I and (P-IMC)II) and eutectic iron-rich phases (plate-shaped, net shape, and fish-bone shape), were found in HPDC AlSi10MnMg. Coarse (P-IMC)I formed in the shot sleeve were distributed in the interface between primary α-Al and binary Al-Si eutectic. Small size (P-IMC)II and various eutectic iron-rich phases formed in the die cavity and they were distributed in Al-Si binary eutectic. The primary iron-rich phases belonged to a simple cubic crystal structure with a lattice constant a = 1.265 nmand they exhibited a lateral growth characteristic with a termination of {110} surface along a (P-IMC)II [1¯12¯] direction. β phase was surrounded by δ phase and they coexisted in a plate-shaped iron-rich phase. High-density stacking fault in β phase and δ/β interface provided an excellent nucleation site for δ phase. From mechanical behavior, the stress concentration caused by eutectic iron-rich phases was far less than (P-IMC)I and it would not cause crack initiation along the eutectic cluster boundary. In addition, (P-IMC)I showed the worst deformation coordination with primary α-Al while the plate-shaped eutectic iron-rich phase exhibited similar deformation characteristics with silicon particles.

The quality improvement of welded joints of die-cast Al alloys using oscillation and current modulation of the electron beam

The issues of the difficult weldability of the high-pressure die-cast aluminum alloys - AlSi10Mg(Fe) were studied within the presented paper. The metallographic, CT, and EDX analyses of castings were performed to identify potential origins of weld joint imperfections and deteriorated weldability. A comparative welding test of welding gravitation die-cast alloys was accomplished to review the influence of the melting process on the weld quality. The casting process was analyzed and several mediums were evaluated as potential sources of material contamination. The selected contaminants were intentionally introduced into the weld joints. The research on welding process improvement and the reduction of the susceptibility to the presence of impurities was accomplished in the next step. The aim of the experiments was the use of dynamic deflection of the electron beam and pulse modulation of its power. The influence of different oscillation frequencies, amplitudes, and patterns was examined. The verified technology was developed, based on the achieved results.