Relationships between Processing and Properties of Magnesium-Based Alloys

Editoria

Microstructure and mechanical properties of new die-cast quaternary Al-Cu-Si-Mg alloys

Engineering and Physical Sciences Research Counci

In situ synchrotron radiation diffraction investigation of the compression behaviour at 350 °C of ZK40 alloys with addition of CaO and Y

The evolution of the microstructure during compression is investigated with in situ synchrotron radiation diffraction in as-cast ZK40, ZK40-2CaO and ZK40-1Y Mg alloys. The specimens were compressed at 350 °C with a strain rate of 10−3 s−1 until 30% deformation. The Y containing alloy showed the highest 0.2% proof strength in compression of 35 MPa at 350 °C which is double that of the ZK40 alloy, while the CaO added alloy shows a moderate increment at 23 MPa. The Y containing alloy shows some work hardening, while the CaO modified and the ZK40 alloys do not show work hardening after yield. Synchrotron radiation diffraction timelines show that continuous and discontinuous dynamic recrystallization occurs during deformation of the ZK40 alloy while a small amount of dynamic recrystallization was observed in the ZK40-1Y alloy. However, dynamic recrystallization was not present in the ZK40-2CaO alloy. SEM-EBSD analysis conducted on the deformed samples shows a significantly high volume fraction of twins in the Y and CaO containing alloys which was absent in the ZK40 alloy. The modified deformation behaviours observed in the CaO and Y containing alloys were attributed to the presence of intermetallic particles found at the grain boundaries and to the role of Ca and Y in stabilising twinning.The authors acknowledge the Deutsches Elektronen-Synchro-tron for the provision of facilities within the framework of proposal I-20130434.RHBacknowledgesUniversityofSãoPaulofor granting the fellowship 'Bolsa Empreendedorismo'

Interactions of CaO with pure Mg and Mg-Ca alloys—an in situ synchrotron radiation diffraction study

Data availability statement: The data cannot be made publicly available upon publication because no suitable repository exists for hosting data in this field of study. The data that support the findings of this study are available upon reasonable request from the authors.CaO additions are used as an inexpensive replacement for Ca in Mg alloys. CaO dissociation in Mg has been reported in literature without a clear mechanism as to why this occurs. In situ synchrotron radiation diffraction investigation of the melting and solidification of Mg with CaO shows, that the stability of CaO was overestimated in Mg melts compared with MgO. The experiments that were performed on the Mg-20CaO and Mg-xCa-6CaO (x = 6 and 16 wt.%) alloys, show the dissociation and formation of various phases during melting and solidification. The results indicate that Mg can reduce CaO even in the solid state, which is the opposite of that proposed by the Ellingham diagrams for stoichiometric reaction. Phase formations during the in situ experiment are compared with published thermodynamic calculations for the interaction between Mg-Ca alloys and oxides.The authors acknowledge the Deutsches Elektronen-Synchrotron (DESY) in Hamburg, Germany, for the provision of synchrotron radiation facilities within the framework of the proposal I-20130330 and the Federal Ministry for Economic Affairs and Energy (BMWi) for funding the project MagHyM (20K1107B)

Microstructure and Mechanical Properties of Ultrafine Quaternary Al-Cu-Si-Mg Eutectic Alloy

Copyright: © 2021 by the authors. The microstructure evolution and mechanical properties of quaternary Al-Cu-Si-Mg eutectic alloy prepared via arc melting and suction casting were studied. This alloy exhibits a single endothermic DSC peak with a melting temperature of 509 °C upon heating, suggesting a eutectic reaction. The cast alloy microstructure consisted of four phases, α-Al, Al2Cu (θ ), Si and Al4Cu2Mg8Si7 (Q), in the eutectic cells and also in the nano-scale anomalous eutectic in the intercellular regions. The eutectic cells show different morphologies in different parts of the sample. Well-defined orientation relationships between the α-Al, Al2Cu, and Q phases were found in the eutectic cell centres, while decoupled growth of Q phase occurred at the cell boundaries. The bimodal microstructure exhibits excellent compressive mechanical properties, including a yield strength of 835 ± 35 MPa, a fracture strength of ~1 GPa and a compressive fracture strain of 4.7 ± 1.1%. The high strength is attributed to a combination of a refined eutectic structure and strengthening from multiple hard phases.Engineering and Physical Sciences Research Council (EPSRC) for the financial support on Future Liquid Metal Engineering (LiME) Hub (EP/N007638/1)

Die-cast multicomponent near-eutectic and hypoeutectic Al–Si–Ni–Fe–Mn alloys: Microstructures and mechanical properties

Data availability: The authors do not have permission to share data.Supplementary data is available online at https://www.sciencedirect.com/science/article/pii/S092150932300401X?via%3Dihub#appsec1 .Copyright © 2023 The Authors. Microstructures and mechanical properties of near-eutectic and hypoeutectic Al–Si–Ni–Fe–Mn alloys were studied under as-cast condition. Near-eutectic 78Al15Si4Ni2.5Fe0.5Mn (wt.%) and hypoeutectic 83.6Al11Si3Ni1.9Fe0.5Mn (wt.%) alloys were processed by high pressure die casting. These two alloys have the same ternary eutectic mixture of α-Al, Si and Al6(FeNiMn) with a melting point of 567 °C. Primary intermetallic phases of block-like Al17(FeNiMn)4Si and plate-like Al4(FeNiMn)Si2 in these two alloys were observed. Precipitates of Si and Ni-contained phase coexist in primary α-Al grains of hypoeutectic alloy. The lattice parameters of Al6(FeNiMn), Al17(FeNiMn)4Si, and Al4(FeNiMn)Si2 phases are slightly changed compared with orthorhombic Al3Ni, orthorhombic Al5.6Fe2 and tetragonal FeAl3Si2 phases from the database, respectively. These two alloys have excellent mechanical properties at high temperatures. The ultimate tensile strength (UTS) at 300 °C ranges from 135 ± 6 MPa (hypoeutectic alloy) to 157 ± 6 MPa (near-eutectic alloy), which is superior to commercial A383 alloy and some other heat-resistant alloys. Therefore, these near-eutectic and hypoeutectic Al–Si–Ni–Fe–Mn alloys have huge potential for industrial application at elevated temperatures.Engineering and Physical Sciences Research Council (EPSRC) Future Liquid Metal Engineering (LiME) Hub (EP/N007638/1)

On the influence of solution and ageing treatments on the microstructure of ZK40 alloys modified with Ca, Gd, Nd and y additions

Abstract As-cast ZK40 alloys, modified with the addition of CaO, Gd, Nd and Y were investigated. Solution heat treatments were performed based on differential thermal analysis results. The unmodified ZK40 alloy exhibited microstructure with nearly no intermetallic compound but with precipitates formed during the solution treatment. The modified ZK40 alloys exhibited a semi-dissolved network of intermetallic compounds along the grain boundaries and zones of intermetallic compounds within the grains. Interestingly, no precipitates were observed immediately next to the grain boundaries. The energy dispersive X-ray spectroscopy line scans showed an enrichment of Zn and Zr in the regions where the precipitates are found, suggesting that they are Zn-Zr precipitates. The ageing behaviour was compared between the as-cast and the solution treated materials and it was found that apart from the ZK40-Gd, ZK40-Nd and ZK40-Y aged at 200 °C after solution treatment, there is no notable ageing response for the investigated alloys.</jats:p

Thixomolded AZ91D and MRI153M magnesium alloys and their enhanced corrosion resistance

© 2020 The Authors. Materials and Corrosion published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim AZ91D and MRI153M alloys were produced by thixomolding. Their corrosion resistance is significantly higher than that of similar materials produced by ingot or die-casting. A corrosion rate smaller than 0.2 mm/year in 5 wt% NaCl solution is measured for the thixomolded AZ91D alloy. The corrosion behaviour was evaluated using immersion tests, electrochemical impedance spectroscopy, hydrogen evolution, glow discharge optical emission spectroscopy, and atomic emission spectroelectrochemistry. A bimodal microstructure is observed for both alloys, with the presence of coarse primary α-Mg grains, fine secondary α-Mg grains, β-phase, and other phases with a minor volume fraction. The amount of coarse primary α-Mg is significantly higher for the AZ91D compared with the MRI153M. The network of β-phase around the fine secondary α-Mg grains is better established in the thixomolded AZ91D alloy. A combination of several factors such as the ratio of primary to secondary α-Mg grains, localised corrosion or barrier effect due to other phases, as well as regions of preferential dissolution of the α-Mg due to chemical segregation, are thought to be responsible for the high corrosion resistance exhibited by the thixomolded AZ91D and MRI153M.German Ministry of Education and Research; Christian Doppler Societ