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•Morphology of various phases of the HPDC AlSiMgMnCu alloy in 3 zones were revealed and quantitatively analyzed by SBFSEM.•The α-Fe and β-Mg2Si phases in the segregation band and ...central zone are rotated and fragmentized by the shearing stress.•The morphology of the Q and θ phases are mainly determined by the morphology of the α-Al and eutectic Si phases.
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.
•Porosity in the HPDC is inevitable and dominants mechanical property variability.•A critical pore size of 0.3 mm is acceptable for applications of HPDC castings.•The elongation of the A356 alloys ...increases as the largest pore size decreases.•The total volume porosity of the alloy declines with increasing elongation.
To reveal the influence of porosity on the variability in mechanical properties of HPDC Al alloys, micro computed tomography was employed to investigate the morphology and 3D distribution of porosity in the tensile samples. Experimental results show that the variability in mechanical properties of HPDC AlSi7MgMn alloy is related to the pore size and total volume of the porosity. The maximum pore size is inversely proportional to the elongation of the alloy with T6 heat treatment, while the total volume porosity was found to decline with increasing elongation. A maximum pore size of approx. 1.3 mm in diameter was found to correspond to an elongation of 6.4%. Once its maximum size reduced to less than 0.3 mm, the elongation was found to improve to 9%-13.5% for the alloy. Compared to the average value of 8.8%, 236.6 MPa, 296.0 MPa for elongation, yield strength and ultimate tensile strength respectively for the porosity-free AlSi7MgMn samples produced by gravity casting, the HPDC AlSi7MgMn alloy has the similar strength level and improved elongation to an average level of 11.5%. This indicates that the porosity level is a determined factor to the mechanical property variability and its size less than 0.3 mm has no significant adverse effect on the mechanical properties of the alloy. The elongation improvement in HPDC AlSi7MgMn alloy is attributed to the finer grain size with an average value of 10 μm compared to the average value of 500 μm for the gravity casting AlSi7MgMn alloy, and to the reduced size and uniform distribution of porosity resulting from the subsequent refinement in grain size.
The present work focusses the attention on a reliable methodology aimed at improving the performance of a complex process, such as the high pressure die casting (HPDC), characterized by multiple ...interactions among several process parameters. Within the context of such a complex system, in which the diversity of the components to be manufactured is among the key factors to be considered, the availability of an accurate predictive maintenance algorithm is of huge importance. In fact, the main advantages are the prevention of unexpected equipment failures as well as the enhancement of the customers’ services. According to these aspects, a data-driven approach has been applied to effectively predict and schedule the necessary maintenance of a HPDC machine used for the manufacturing of accessories and component for doors and window applications. Two approaches were investigated: from one side, a more comprehensive approach considered the whole set of monitored parameters and the algorithm was trained to predict the Remaining Useful Life (RUL), i.e. the residual number of injection before the subsequent machine downtime for the maintenance operations. On the other side, a more simplified approach was developed to predict the evolution of a direct parameter (the sprue height SM) via a time-series forecasting.
Fabrication of aluminum alloy components by traditional high-pressure die casting (HPDC) requires cost- and time-consuming tooling of steel dies, which makes HPDC uneconomic for producing low-volume ...components or prototypes. In comparison, powder bed-based additive manufacturing, e.g. selective laser melting (SLM), enables rapid prototyping and production of even complex-shaped components directly from computer-aided design models without needing expensive tools. However, SLM prototype components must have almost identical mechanical properties to HPDC serial components in order to emulate their functionality under different load conditions. In this work uniaxial tensile properties of cast alloy AlSi10MnMg (EN AC-43500) in condition T7, i.e. with 120-170 MPa yield stress, 200-240 MPa tensile strength and 9-12 % strain at fracture, shall be attained using selective laser melting of powder alloy AlSi10Mg (EN AC-43000). These properties were achieved by tailored heat treatment. Furthermore, the effect of hot isostatic pressing (HIP) was investigated. The results of the tensile tests confirmed the basic feasibility of substituting HPDC components with SLM components for prototyping. In particular, similar tensile strength and uniform strain were achieved for SLM samples in condition O, i.e. for SLM samples which were only annealed.
•Samples tested in Al die soldering tests showed similar behavior to industrial die molds.•Al corrosion tests present more pronounced corrosion than real molds and dies.•AlCrN PVD coating reduces the ...Al reaction and extraction stresses of H13 tool steel.•Dissolution of the H13 at stress concentration regions make the surface prone to fatigue failure.
High-pressure die casting (HPDC) is regularly used to produce aluminum components. The die-casting molds are subjected to severe localized corrosion due to contact with the hot melted aluminum (700 °C) and accelerated by the intense thermal cycling generated by the cooling system. The correct understanding of each failure mode that occurs during the operation of these molds can increase tool life and reduce operational costs. Different components used in aluminum components production were evaluated after completing their useful tool life, and the failure modes were compared with two high-temperature laboratory tests, molten aluminum corrosion and die soldering tests. The primary crack mechanism observed in the HPDC die was heat checking, with a surface reaction of the tool steel with the molten aluminum. PVD coating increases the die's tool life, reducing the reactivity with the molten aluminum, which was observed in both laboratory tests. Die soldering tests represent the die mold behavior in HPDC production, showing a similar intermetallic phase and crack formation. Laboratory corrosion tests showed a more aggressive corrosion behavior than that observed in molds and dies used in HPDC industrial production.
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•Shrinkage induced by ESCs is an important crack initiating source.•Lower vacuum pressure was achieved via longer vacuum time.•The developed flow distributer blocked most ESCs from ...entering die cavity.•Mechanical properties were significantly improved.
Significantly improved mechanical properties of the AZ91D alloy, i.e., ∼20% higher ultra tensile strength, double elongation and treble low-cycle fatigue life, were achieved by employing a specially designed flow distributer during the vacuum-assist high pressure die casting (HPDC) process. The application of vacuum in HPDC could significantly improve the mechanical properties of the components by reducing the gas pores. In addition, by employing the specially designed flow distributor, the external solidified crystals (ESCs) could be effectively blocked from entering the die cavity, which significantly reduced the magnitude scattering of the mechanical properties. By applying the vacuum and the flow distributor, the HPDC samples exhibited a microstructure with substantially high uniformity, i.e., ∼90% lower porosity and ∼80% less ESCs than those of conventional HPDC samples. Tensile and fatigue tests showed that the initiation of the crack, i.e., the primary mechanism determining the sample failure, was highly sensitive to the shrinkage pores connected with gas pores and the large and complex shrinkage pores induced by ESCs.
Studies of deep cryogenic treatment have mainly focused on ferrous alloys, despite the advantages of this form of treatment when applied to other non-ferrous alloys. This study examines the ...microstructural behavior of a high pressure die-casting (HPDC) AZ91 magnesium alloy, submitted to T6 and T6 with deep cryogenic treatment (DCT) prior to aging. Differences between continuous and discontinuous β-Mg17Al12 phase precipitation are analyzed by means of TEM, SEM and optical microscopy to explain the mechanical behavior following each type of heat treatment. The mechanical properties were improved by both treatments though yield strength was higher following T6 treatment and elongation was greater following T6 with deep cryogenic treatment. The conclusion is that continuous precipitation is promoted by cryogenic treatment, resulting in an improvement of elongation by 20%. This factor is important in view of the limitations of poor plasticity and its consequences for HPDC magnesium alloy applications.
Effects of 2 wt% Gd addition on microstructures and tensile properties of a high-pressure die casting (HPDC) Mg–4Al–3La−0.3Mn (wt.%) alloy were studied. The newly developed alloy owns much finer ...grains than commercial/experimental HPDC Mg alloys. Furthermore, it contains various intermetallic phases, namely η-Al3(La,Gd), Al2(Gd,La) or Al2(La,Gd), Al7(La,Gd)3 and Al2.12(La,Gd)0.88, among which Al7(La,Gd)3 was experimentally observed in Mg–Al−RE-based alloys for the first time. Moreover, both η-Al3(La,Gd) and Al2(Gd,La) present two or more morphologies due to different chemical compositions. Finally, the studied alloy exhibits more excellent tensile properties than commercial/experimental HPDC Mg–Al-based alloys. The underlying causes for grain refinement, variety of intermetallic phases, as well as excellent tensile properties were discussed and revealed.
The alloying effects of small additions of Sc, Zr, Cr on the microstructure and mechanical properties of Al-5Mg-2Si casting alloys produced by High Pressure Die Casting (HPDC) were investigated. The ...microstructure of the Al-alloys consists primarily of the α-Al and Al-Mg2Si eutectic cells and the α-Al15(Mn,Fe)3Si2 intermetallic phase as well as coarse Al7Cr and Al3Zr intermetallic phases. The most significant improvement in the mechanical properties was achieved in the alloys with Sc + Cr and Sc + Zr additions. Alloying with 0.2 wt% of Sc in combination with Zr and Cr additions exhibits the best combination of strength and ductility with a yield strength of 206 MPa, an ultimate tensile strength of 353 MPa and an elongation of 10% in the as-cast condition. Alloys with Cr + Zr addition have a higher hardness and tensile strength compared to the AlMg5Si2Mn base alloy (commercially known as “Magsimal-59”) and the similar levels of yield strength and elongation. However, they have lower levels of all set of properties compared to the alloys with Sc + Cr and Sc + Zr additions, due to the presence of coarse Al7Cr sludge and Al3Zr intermetallic phases.
•Al7Cr, Al3Zr phases were detected in the alloys with addition of Cr (0.2 wt. % and higher) and Zr (0.1 wt. % and higher);•Al3Sc phase with irregular shape was observed in the interdendritic space of the alloys with Sc+Zr and Sc+Cr additions;•Sc+Zr and Sc+Cr additions have the most prominent effect on the mechanical properties as compared to Zr+Cr additions.
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