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The objective of this study was to examine the impact of varying magnesium levels in the α-Al + S + T region of the Al-Cu-Mg ternary phase diagram on the solidification process, microstructure development, tensile properties, and precipitation hardening of Al-Cu-Mg-Ti alloys. The outcomes indicate that alloys with 3% and 5% Mg solidified with the formation of binary eutectic α-Al-Al2CuMg (S) phases, whereas in the alloy with 7% Mg, the solidification process ended with the formation of eutectic α-Al-Mg32(Al, Cu)49 (T) phases. Additionally, a significant number of T precipitates were noticed inside the granular α-Al grains in all alloys. In the as-cast condition, the 5% Mg-added alloy showed the best combination of yield strength (153 MPa) and elongation (2.5%). Upon T6 heat treatment, both tensile strength and elongation increased. The 7% Mg-added alloy had the best results, with a yield strength of 193 MPa and an elongation of 3.4%. DSC analysis revealed that the increased tensile strength observed after the aging treatment was associated with the formation of solute clusters and S″/S′ phases.

In this study, using transmission electron microscopy and phase diagrams from thermodynamic calculations, we investigated the oxide film formation of Al–7.5 mass%Mg alloy containing Ca traces during short-term oxidation in terms of the thermodynamic stability and multi-element oxides by inter-diffusion based on the results of analysis for the oxide film. For the oxidation test at 515 ˚C, for 1 h, its results showed that there is no significant difference between the Ca-added and Ca-free Al–7.5 mass%Mg alloys was observed, while further exposure caused the Ca-free alloy to gain significant weight. Based on the standard Gibbs free energy for oxide production calculated in this study, CaO was the most preferential product among the single metal oxides examined. As per calculations for MgAl2O4-spinel formation reactions, the spinel formation from MgO was thermodynamically the most favorable. According to the phase diagrams calculated in this study, various multi-element oxides including Ca could possibly form in the oxide layer of Ca-added alloy. The analysis results of transmission electron microscopy confirmed that MgO is the primary oxide in the Al–Mg binary alloys. In oxidation tests conducted for less than 1 h, the spinel was rarely found. The outmost areas of oxide layers correspond to MgO and CaO in Ca-free and Ca-added alloys, respectively. However, in the Ca-added alloy, the inner layer contains certain amounts of Ca, Al, and Mg.

In this study, the effects of Ca addition on the microstructure, thermal properties, and mechanical properties of a Mg-6.0Zn-1.2Y-0.7Zr (ZWK611) alloy at room temperature and 150 °C were investigated. With an increase in the Ca content, the ignition resistance of the ZWK611 alloy improved and the grains became finer. The as-cast ZWK611 alloy consisted mainly of the dendritic α-Mg matrix and I-phase (Mg3Zn6Y) at the grain boundaries. On the other hand, the τ- (Ca2Mg6Zn3) and I-phases were formed in the Ca-added ZWK611 alloy. The fraction of the τ-phase increased with an increase in the Ca content. After the solid-solution treatment, these phases remained partially at the grain boundaries of the Ca-added ZWK611 alloys and an additional W-phase (Mg3Zn3Y) was observed. The phases remaining at the grain boundaries restricted the grain growth through the grain boundary pinning effect. The aging treatment resulted in the formation of MgZn' precipitates in the α-Mg matrix of the alloys. These precipitates were more uniformly distributed in the Ca-added alloys than in the alloys without Ca. Thus, the heat treatment-induced precipitation improved the tensile and creep properties of the T6-treated alloys. The T6-treated ZWK611+0.7Ca alloy exhibited the best mechanical properties at room temperature and 150 °C among all the tested alloys.

In this study, we investigated the effect of Mg on oxide growth of Al-Cu alloys at elevated temperatures. Results show that Al2Cu as eutectic phase was distributed in the as-cast microstructure of Mg-free Al-5 mass%Cu alloy, whereas Al2CuMg_S phase was formed by eutectic reactions with the addition of Mg. Scanning electron microscopy and thermodynamic calculations revealed that after oxidation at 500 °C for 30 h, Al-5 mass%Cu alloy had only slightly oxidized surfaces, whereas significantly grown oxide clusters formed as the Mg content increased. MgO and spinel were the main oxides in the Mg-containing alloys, whereas no Cu-based oxide was involved in the oxidation of the alloys. Only Al2CuMg_S phase contributed to the oxidation of the base metal and the formation of Mg-based oxides. The Al-5 mass%Cu alloy showed no inter-products with Mg-based oxides, including MgO and spinel.

In this study, the oxidation of Al–Mg alloys with Mg content ranging from 3 mass% to 5 mass% at a high temperature was re-examined using phase diagrams was re-examined using phase diagrams plotted using thermodynamic software. The as-cast microstructures of all examined alloys showed the formation of the β–Al3Mg2 phase, and especially, its phase fraction considerably increased with increasing Mg content up to 5 mass% from 3 mass%. After oxidation at 500 °C under the ambient atmospheric conditions for 50 h, all the oxidized cross-sections had coarse and dark areas nonuniformly distributed in the matrix, which were found to be the oxide clusters containing Mg-based oxides. With increasing Mg content, the higher Mg content was involved in promoting the growth of Mg-oxide clusters and possibly associated with the change in the fraction of the β–Al3Mg2 phase. The Al–5 mass%Mg alloy formed higher fractions of MgO and spinel during the oxidation.

Studies to investigate the oxidation behavior of Al–Mg alloys with Al-5 mass%Ti-1 mass%B master alloy as a grain refiner at high temperature were conducted. The Scheil-Gulliver cooling calculation showed that, in 0.2 mass%Ti-inoculated alloy, TiAl3 was formed before the primary Al formation, which may act as a grain refiner. The optical microstructures showed a significant grain refinement after the addition of 0.2 mass%Ti using Al-5 mass%Ti-1 mass%B master alloy. Moreover, the oxidized cross-sections, throughout the oxidation time, show coarse and dark areas (regarded as oxide clusters), which were nonuniformly distributed in the matrix after oxidation at 500 °C under an ambient atmosphere. In addition, an accumulation of oxygen by diffusion for a long duration led to the growth of blisters after 50 h. At the oxidation temperature, Mg3Ti2Al18 was found to be only stable Ti-containing phase and possibly formed MgO by the interaction with the diffused oxygen.

The effect of the phase fraction ratio between Al3Mg2 and Mg2Si on the oxidation resistance of Al–Mg–Si alloys at high temperatures was investigated. With addition of 1 mass%Si in Al-6 mass%Mg alloy, the as-cast microstructures showed formation of Mg2Si phase by eutectic reactions. With increasing Si content more than 3 mass%, the Mg2Si and Si are formed as eutectic phases with no β-Al3Mg2 phase. In addition, with an increase in the Si content from 3 mass%, significantly refined as-cast microstructures and distribution of extended eutectic phase areas were observed. The oxidized cross-sections of Al-6 mass%Mg and Al-6 mass%Mg-1 mass%Si alloys showed coarse and dark areas, which are considered as oxide clusters, nonuniformly grown into the matrix. However, Al-6 mass%Mg-3 mass%Si and Al-6 mass%Mg-5 mass%Si alloys had no significantly grown oxide clusters on the surfaces. Based on the results, it was concluded that the reduction of the ratio between β-Al3Mg2 and Mg2Si phases can reduce the rapid oxidation of Mg.

This study examined the microstructural evolution and castability of Al–Mg–Si ternary alloys with varying Si contents. Al–6Mg–xSi alloys (where x = 0, 1, 3, 5, and 7; all compositions in mass pct) were examined, with Al–6 mass pct Mg as a base alloy. The results showed that in the ternary alloys with Si ≤ 3 pct, the solidification process ended with the formation of eutectic α-Al–Mg2Si phases generated by a univariant reaction. However, in the case of ternary alloys with Si > 3 pct, solidification was completed with the formation of α-Al–Mg2Si–Si ternary eutectic phases generated by a three-phase invariant reaction. In addition to the eutectic Mg2Si phases, the primary Mg2Si phases formed in each of the ternary alloys, and the size of both sets of phases increased with increasing Si content. The two-phase eutectic α-Al–Mg2Si nucleated from the primary Mg2Si phases. The inoculated Al–6Mg–1Si alloy had the smallest grain size. Moreover, the grain-refining efficacy of the Al–5Ti–B master alloy in the ternary alloys decreased with increasing Si content in the alloys. Despite the poisoning effect of Si on the potency of TiB2 compounds in the inoculated Al–6Mg–1Si alloy, the grain size of the alloy was slightly smaller than that of the Al–6Mg binary alloy. This resulted from the increasing growth restriction factor (induced by Si addition) of the Al–6Mg–1Si alloy. In terms of the castability, the examined alloys showed different levels of susceptibility to hot tearing. Among the alloys, the ternary Al–6Mg–5Si alloy exhibited the highest susceptibility to hot tearing, whereas the Al–6Mg–7Si exhibited the lowest. The severity of hot tearing initiated by the unraveling of the bifilm was determined by the freezing range, grain size, and the amount of eutectic phases at the end of the solidification process.

The effect of tailored microstructures in 0.5 wt% CaO added AZ31 on tensile, high-cycle fatigue, and fatigue crack growth properties was examined. By adding CaO, the average grain size (AGS) was significantly reduced from 4.25±2.32 μm (conventional AZ31) to 2.42±1.60 μm (CaO-AZ31). The fineprecipitates of CaO-AZ31 were more evenly distributed and their fraction was higher than those of conventional AZ31. The fine-precipitates were identified as Al8Mn4Ca and (Mg, Al)2Ca in CaO-AZ31, meanwhile, were identified as Al8Mn5 and Mg17Al11 in conventional AZ31. The tensile test results showed that the yield strengths of CaO-AZ31 and conventional AZ31 were 238.0 MPa and 206.7 MPa, respectively. The elongation-to-failure also increased when CaO was added. The improved tensile properties of CaO-AZ31 could be explained by grain refinement and precipitation hardening. The high-cycle fatigue limit also increased about 15% with added CaO. The fatigue limits as a function of the tensile strengths of CaO-AZ31 and conventional AZ31 were 0.508 and 0.457, respectively. The origin of the improved fatigue resistance was attributed to inhibition of the formation of DTs, which acted as the fatigue crack source, in CaO-AZ31. In contrast, the fatigue crack growth property did not change when CaO was added. Based on the above findings, the relationships between microstructure, mechanical properties and deformation mechanisms are also discussed.

In this study, the effects of constituent phases on the oxidation kinetics of an Al-7 mass%Mg alloy containing a trace of Ca were investigated. A Mg+Al2Ca master alloy was used to add Mg and Ca simultaneously. Scheil-Gulliver cooling by thermodynamic calculation showed that the addition of Ca led to the formation of Ca-based intermetallic compounds, such as Al4Ca and Laves C36, after solidification. Based on weight increase indicated by the oxidation test and surface analysis, it was found that the presence of Ca-based phases significantly improved the oxidation resistance and slowed down the oxidation rates. Based on the review of phase diagrams with oxygen partial pressure by thermodynamic calculation, it was thought that in the initial oxidation, MgO and MgAl2O4 were formed on the surfaces of the Al–Mg alloys, leading to further oxidation. The Ca-based intermetallic compounds formed Ca–Mg–Al based oxides, which possibly contributed to the formation of a relatively dense oxide layer.

In this study, the oxidation behavior of Cu alloys containing two alkaline earth metals (i.e., Mg and Ca) at 500 °C was investigated. The Mg+Mg2Ca master alloy was used for the simultaneous addition of Mg and Ca into Cu. As a result of the oxidation test, all examined samples showed weight gains that followed parabolic laws. Mg addition in Cu considerably slowed down the oxidation rate, while the use of the Mg+Mg2Ca master alloy as an alloying element for Mg led to an even further reduction in the oxidation rates at the testing temperature. The phase diagrams with the oxygen partial pressure showed that the Ca and Mg-containing alloy resulted in the formation of CaO as the primary oxide and MgO as the secondary oxide. The improved oxidation resistance can be attributed to the mixed surface layer of CaO and MgO, which control the growth rate of Cu2O.

In this study, the correlation of surface oxidation and Mg-based intermetallic phases in the grain boundary in Al–Mg alloys containing third elements was investigated. The experimental results were examined by phase diagrams plotted as a function of oxygen partial pressure determined by thermodynamic calculation. The addition of Si and Cu as third elements into the Al–7 mass%Mg alloy formed Mg-based secondary phases during solidification. The 1 mass% Cu addition formed three different types of Mg-based intermetallic compounds. From weight gains by oxidation, all samples exhibited their weight gains depending on time. The Si-added alloy showed a considerably lower weight gain and maintained a nearly constant weight, while the weight gain of the Al–7 mass%Mg–1 mass%Cu alloy was significantly greater than those of other alloys. MgO and MgAl2O4− spinel were the main oxides that formed the oxide scale in all examined alloys. Si addition formed the multi-element oxide including Mg and Si.

Three alloys (Mg–6Zn–1.2Y, Alloy I; Mg–3.65Zn–1.65Y, Alloy II; and Mg–4.3Zn–1.4Y, Alloy III) with same volume fraction and grain size were designed to evaluate the effects of the I-phase (Mg3Zn6Y) and W-phase (Mg3Zn3Y2), which are the major phases in Mg–Zn–Y alloys, on the mechanical properties. The tensile strength of Alloy I with the I-phase at room temperature was the highest among the tested alloys because the coherent interface between the I-phase and the α-Mg phase was more resistant to cracking than the incoherent interface between the W-phase and the α-Mg phase. A cross-sectional microstructure analysis of a sample that was tensile-tested at 423 K revealed that the morphology of the I-phase remained relatively stable. In contrast, the W-phase was broken and fragmented during the tensile test at 423 K because it had higher brittleness under the test conditions. Therefore, the tensile and creep properties of Alloy I at 423 K were better than those of Alloys II and III containing the W-phase. According to the results, the I-phase in the Mg-Zn-Y alloy was more beneficial to the mechanical properties at room temperature and 423 K than the W-phase.

Effects of a minor Ca addition on microstructural stability and dynamic restoration behavior of AlMg5 during hot deformation were investigated. They were studied using scanning electron microscopy (SEM), differential scanning calorimetry (DSC), electron backscatter diffraction (EBSD) analyses and transmission electron microscopy (TEM). JMatPro package was used for simulation of the solidification path of the alloys. The results show that the addition of Ca does not affect the microstructure and hot compression behavior of the as-cast samples. However, it prevents the drastic grain growth during homogenization. It is found that coarse grains of Ca-free alloy promote the dynamic recovery and slow down the dynamic recrystallization during hot compression. Also, the particle stimulated nucleation is suggested as the main nucleation mechanism of new recrystallized grains for hot compressed Ca-free alloy. On the other hand, the microstructure of the hot compressed Ca-added alloy is greatly affected by the presence of Al4Ca intermetallics. The formation of Al4Ca phase is predicted by JMatPro and revealed by DSC, SEM and TEM studies. Finally, it is found that the presence of Al4Ca precipitates on the grain boundaries of Ca-added alloy prevents the growth of α(Al) by Zener pinning effect and results in the stability of microstructure during homogenization.

The aim of this study was to investigate the impact of the addition of a minor quantity of Si on the microstructure evolution, heat treatment response, and mechanical properties of the Al–4.5Cu–0.15Ti–3.0Mg alloy. The microstructure analysis of the base alloy revealed the presence of α-Al grains, eutectic α-Al-Al2CuMg (S) phases, and Mg32(Al, Cu)49 (T) phases within the Al grains. In contrast, the Si-added alloy featured the eutectic α-Al-Mg2Si phases, eutectic α-Al-S-Mg2Si, and Ti-Si-based intermetallic compounds in addition to the aforementioned phases. The study found that the Si-added alloy had a greater quantity of T phase in comparison to the base alloy, which was attributed to the promotion of T phase precipitation facilitated by the inclusion of Si. Additionally, Si facilitated the formation of S phase during aging treatment, thereby accelerating the precipitation-hardening response of the Si-added alloy. The as-cast temper of the base alloy displayed a yield strength of roughly 153 MPa, which increased to 170 MPa in the Si-added alloy. As a result of the aging treatment, both alloys exhibited a notable increase in tensile strength, which was ascribed to the precipitation of S phases. In the T6 temper, the base alloy exhibited a yield strength of 270 MPa, while the Si-added alloy exhibited a significantly higher yield strength of 324 MPa. This novel Si-added alloy demonstrated superior tensile properties compared to many commercially available high-Mg-added Al–Cu–Mg alloys, making it a potential replacement for such alloys in various applications within the aerospace and automotive industries.

In this study, the surface segregation of Mg and Ca in Cu-Mg alloys containing a trace amount of Ca under an oxidative atmosphere and its effects on oxidation resistance were examined. The use of a Mg+Mg₂Ca master alloy as an alloying element for Mg rendered significant surface protection during melting and casting. During solid-state oxidation, the oxidation resistance was increased by the addition of Mg. Ca containing alloys with the same Mg exhibited a relatively higher oxidation resistance. From the phase diagram with the oxygen partial pressure as a function of the Mg content, the Ca containing alloy led to the formation of CaO as the primary oxide. The improved oxidation resistance of Ca containing alloys can be attributed to a mixed surface layer of CaO and MgO.

In this study, effect of Ca on phase stability and oxidation of Al₃Mg₂ at elevated temperature was investigated. From thermogravimetric analysis (TGA) at 420 °C, rapid weight gains in the initial stage and incubation were observed for Al₃Mg₂ and Ca-added Al₃Mg₂. After incubation for some time, Al₃Mg₂ sample exhibited the second weight growth, while Ca added sample exhibited continuous incubation during the testing time. The phase diagrams calculated by Factsage 7.1 revealed that Ca exists as Laves_C36 in Al₃Mg₂ and also forms Ca₃MgAl₄O10, following formation of MgO and MgAl₂O₄-spinel as primary and secondary oxides, respectively, on the surface during oxidation at 420 °C.

The current study investigated the microstructure modification in Al–6Mg–5Si–0.15Ti alloy (in mass %) through the minor addition of Ca using Mg + Al2Ca master alloy and heat treatment to see their impact on mechanical properties. The microstructure of unmodified alloy (without Ca) consisted of primary Al, primary Mg2Si, binary eutectic Al–Mg2Si, ternary eutectic Al–Mg2Si–Si, and iron-bearing phases. The addition of 0.05 wt% Ca resulted in significant microstructure refinement. In addition to refinement, lamellar to fibrous-type modification of binary eutectic Al–Mg2Si phases was also achieved in Ca-added (modified) alloy. This modification was related to increasing Ca-based intermetallics/compounds in the modified alloy that acted as nucleation sites for binary eutectic Al–Mg2Si phases. The dendritic refinement with Ca addition was related to the fact that it improves the efficacy of Ti-based particles (TiAl3 and TiB2) in the melt to act as nucleation sites. In contrast, the occupation of oxide bifilms by Ca-based phases is expected to force the iron-bearing phases (as iron-bearing phases nucleate at oxide films) to solidify at lower temperatures, thus reducing their size. The as-cast microstructure of these alloys was further modified by subjecting them to solution treatment at 540 °C for 6 h, which broke the eutectic structure and redistributed Mg2Si and Si phases in Al-matrix. Subsequent aging treatment caused a dramatic increase in the tensile strength of these alloys, and tensile strength of 291 MPa (with El% of 0.45%) and 327 MPa (with El% of 0.76%) was achieved for the unmodified alloy and modified alloy, respectively. Higher tensile strength and elongation of the modified alloy than unmodified alloy was attributed to refined dendritic structure and modified second phases.

The current study investigated the microstructure modification in Al–6Mg–5Si–0.15Ti alloy (in mass %) through the minor addition of Ca using Mg + Al2Ca master alloy and heat treatment to see their impact on mechanical properties. The microstructure of unmodified alloy (without Ca) consisted of primary Al, primary Mg2Si, binary eutectic Al–Mg2Si, ternary eutectic Al–Mg2Si–Si, and iron-bearing phases. The addition of 0.05 wt% Ca resulted in significant microstructure refinement. In addition to refinement, lamellar to fibrous-type modification of binary eutectic Al–Mg2Si phases was also achieved in Ca-added (modified) alloy. This modification was related to increasing Ca-based intermetallics/compounds in the modified alloy that acted as nucleation sites for binary eutectic Al–Mg2Si phases. The dendritic refinement with Ca addition was related to the fact that it improves the efficacy of Ti-based particles (TiAl3 and TiB2) in the melt to act as nucleation sites. In contrast, the occupation of oxide bifilms by Ca-based phases is expected to force the iron-bearing phases (as iron-bearing phases nucleate at oxide films) to solidify at lower temperatures, thus reducing their size. The as-cast microstructure of these alloys was further modified by subjecting them to solution treatment at 540 °C for 6 h, which broke the eutectic structure and redistributed Mg2Si and Si phases in Al-matrix. Subsequent aging treatment caused a dramatic increase in the tensile strength of these alloys, and tensile strength of 291 MPa (with El% of 0.45%) and 327 MPa (with El% of 0.76%) was achieved for the unmodified alloy and modified alloy, respectively. Higher tensile strength and elongation of the modified alloy than unmodified alloy was attributed to refined dendritic structure and modified second phases.

In this work, the microstructure and corrosion behavior of a novel Al-6Mg alloy were investigated. The alloy was prepared by casting from pure Al and Mg+Al2Ca master alloy. The ingots were homogenized at 420 °C for 8 h, hot-extruded and cold-rolled with 20% reduction (CR20 alloy) and 50% reduction (CR50 alloy). The CR50 alloy exhibited a higher value of intergranular misorientation due to a higher cold rolling reduction ratio. The average grain sizes were 19 ± 7 μm and 17 ± 9 μm for the CR20 and CR50 alloys, respectively. An intergranular corrosion (IGC) behavior was investigated after sensitization by a nitric acid mass-loss test (ASTM G67). The mass losses of both the CR20 and CR50 alloys were similar at early periods of sensitization, however, the CR20 alloy became more susceptible to IGC as the sensitization time increased. Grain size and β phase precipitation were two critical factors influencing the IGC behavior of this alloy system.

For the purpose of applying a modified 5083 alloy (New 5083M alloy) with high Mg content in various automotive sheet parts, the stretch forming behavior of the 5083M alloy was studied in tensile mode at a wide range of processing conditions. The tensile tests were conducted by using a tensile test machine under the temperature ranges of 100–400 °C and the strain rate ranges of 0.001–1 s−1. The test results showed that the 5083M alloy has superior mechanical properties to that of the commercial 5083 alloy at elevated temperatures. The microstructure before and after the stretch forming was analyzed using optical microscope (OM) equipped with a polarizing filter and electron backscattered diffraction (EBSD) unit. Deformed microstructure was observed under low temperature conditions and dynamic recrystallized microstructure under high temperature conditions. However, regardless of microstructure evolution, developed deformation textures were distributed in orientation distribution functions (ODF) images. In addition, at high temperature and low strain rate condition, complex shaped cavities which were detrimental to mechanical properties appeared at the grain boundary and grain triple junction. Based on the test results data, a constitutive equation predicting the deformation behavior of the 5083M alloy was derived. The calculated curves by the constitutive equation were compared with the measured curves by experiment and agreed well.

Solid-state electrolytes are considered as key materials for overcoming the limitations of the liquid-electrolyte-based Li-ion batteries in terms of energy capacity, cyclability, and safety. Among the many possible solid-state electrolyte materials, inorganic sulfides are of intensive research interest mainly because the larger and more polarizable sulfur anions substantially enhance the mobility of cationic Li species. In particular, Li-P-S electrolytes, such as Li10GeP2S12and Li7P3S11, have been reported to have room-temperature Li-ion conductivity of greater than 10-2 S/cm, which is comparable to that of conventional liquid electrolytes. Despite the facile Li-ion transport, the Li-P-S electrolytes tend to undergo irreversible structural degradation within typical operating conditions of the battery. This lack of electrochemical stability leads to the formation of high impedance intermediate transition layers at the electrode/electrolyte interfaces, hindering the practical application of the Li-P-S electrolytes. Partial replacement of the element P with other elements within a Li-P-S structural family can improve the lithium-ion conductivity, but notable improvement in their electrochemical stability has yet to be achieved. Li-M-S (M = transition metals, such as Cr, Zr, Nb, Mo, and Sn) families can be possible candidates for electrochemically stabile solid-state electrolytes, while having excellent Li-ion transport properties of the inorganic sulfides. Like the Li-P-S structure, numerous Li-M-S structural derivatives have already been synthesized by varying the element M or by replacing a portion of the element M with another element, and the Li-ion conductivity and electrochemical stability are expected to be heavily dependent on the element composition and crystalline structure. In this study, we investigate the motion and dynamics of Li-ions in Li-Zr-S and Li-Zn-Zr-S compound electrolyte by performing a series of first-principles calculations. To this end, we generate multiple Li-Zn-Zr-S compound model structures with varying Zr-to-Zn ratios. Then, we evaluate Li-ion conductivities by using velocity auto correlation scheme combined ab initio molecular dynamics (AIMD) simulations. More specifically, we calculate the diffusivity and ionic conductivity of the stoichiometric structure and at a range of defect concentrations on Li2+2xZnxZr1-xS3, from x = 0 to x = 0.5. Our calculation results reveal how the introduction of Zn into the Li-Zr-S compound affects the Li-ion mobilities. The theoretical insight obtained in this study well corroborates with recently reported experimental results for varying ionic conductivities in Li-Zn-Zr-S electrolytes depending on the Zr-to-Zn ratio. This fundamental understanding can be an important theoretical basis for developing practically applicable Li-M-S electrolytes. Figure 1

This study examines the formation of different phases of Al-6 mass% Mg–xCu (x = 1 and 3 mass%) alloys in as-cast condition. Further, it investigates the dissolution of these phases upon solution heat treatment (SHT) and studies the precipitation behavior of these ternary alloys. Scanning electron microscopy with energy-dispersive spectrometry and high resolution X-ray diffraction analyses show the presence of the second phases of Al3Mg2 (β), Al6CuMg4 (T), and Al2CuMg (S) in Alloy I (Al–6Mg–1Cu), whereas Alloy II (Al–6Mg–3Cu) had only T and S second phases (with a much higher number of S phases). Upon SHT, a significant number of eutectic phases were dissolved in Alloy I, whereas in Alloy II, the number of undissolved S phases was relatively high. A differential scanning calorimetry (DSC) analysis of experimental alloys in as-quenched states reveals two exothermic peaks related to the formation of nanoclusters and S″ or S′ metastable phases. Both alloys undergo a rapid hardening stage during the aging process, in which approximately 50%–60% of total hardness was achieved. This is attributed to the formation of nanoclusters. The maximum yield strength achieved at the peak hardness condition was approximately 200 MPa for Alloy I, whereas it was approximately 160 MPa for alloy II. Alloy I took a long time to reach peak hardness, which is correlated with the stability of nanoclusters for a longer time. Earlier peak hardness in Alloy II, despite having nanoclusters, is correlated with undissolved eutectic phases acting as heterogeneous nucleation sites for the formation of S″ or S′ metastable phases.

This study investigated the heat treatment response and tensile properties of Al–6 mass%Mg–xSi (x = 1, 3, 5, and 7 mass%) ternary alloys. Further, the fracture behavior of these alloys in response to heat treatment for different temper conditions was also examined. Scanning electron microscopy–energy dispersive X-ray spectrometry (SEM–EDS) analysis of the as-cast alloys revealed, in all of them, the presence of iron-bearing phases (in a size range of 10˜60 μm) that did not dissolve or become refined upon heat treatment. Additionally, eutectic Mg2Si and Al3Mg2 phases were found in Alloy I (Al–6Mg–1Si), while eutectic Mg2Si and Si phases were found in the rest of the alloys. In the as-cast condition, the tensile properties of the examined alloys decreased in relation to increasing Si content. Nonetheless, after heat treatment, the yield strength of the alloys with high Si content (>3 mass%) increased significantly compared with that in the as-cast condition. A yield strength greater than 300 MPa was achieved in both Alloy III (Al–6Mg–5Si) and Alloy IV (Al–6Mg–7Si), although this was achieved at the expense of ductility. According to the fractography of the tensile-fractured surfaces undertaken using optical and scanning electron microscopy, fractures of the iron-bearing phases were found to be the source of cracking in alloys with high Si content. In the case of those with low Si content (≤3 mass%), cracks were believed to have been caused by the debonding of iron-bearing phases from the aluminum matrix.

In this study, the combined effect of Mg and Ca on the high temperature oxidation behaviors of Zn–Mg based alloys containing trace Ca was investigated. Phase diagrams for the oxygen partial pressure versus contents of constituent elements were conducted on the basis of thermodynamic calculations to predict oxide scale behavior. Observation of Zn-1/3/5 mass%Mg alloys showed the distribution of a Zn–Zn11Mg2 eutectic phase after primary formation. As-cast microstructures of the Ca-containing alloys included the formation of a Ca-based intermetallic phase. The change in oxidation resistance with variation of the Mg and Ca contents was experimentally examined via thermogravimetric analysis (TGA). The addition of trace Ca led to the formation of Zn13Ca and a CaO/MgO mixed oxide layer on the surface at 460 °C. After TGA at 460 °C under air atmosphere for 1 h, the Ca-free alloys showed rapid weight gain by oxidation, whereas the oxidation resistance of the Ca-added alloys was substantially increased.

Changes of strength and ductility in a hypoeutectic Al-7mass%Si-Mg with increasing Mg content and Al-7.5mass%Mg alloys with increasing Ca content were investigated. The elongation of Al-7.5mass%Mg alloy was improved with increasing Ca content up to 0.1mass% without trade-off with the strength. With increasing Mg and Ca contents simultaneously, the Al-7mass%Si alloys showed the modification of eutectic Si particles. After aging, the alloys had the distribution of residual Mg2Si in their grain boundaries with increasing Mg content over the Mg solubility. Al-7mass%Si-0.8mass%Mg alloy including a small amount of residual Mg2Si showed a significant improvement of strength after the aging

This study examined the effect of Ca addition on the selective oxidation of the Al3Mg2 phase in an Al-5 mass%Mg alloy during oxidation at 400 °C and 500 °C for 72 h. Ca addition led to the formation of the Al4Ca and Laves_C36 phases besides the primary Al solid solution and Al3Mg2. After the oxidation test, there was no significant oxidation in both the Ca-free and Ca-added alloy samples and no visible change in the surfaces between them at 400 °C, which is lower than the melting temperature of Al3Mg2 (451 °C). At 500 °C, the surface of the Ca-free alloy showed the formation of oxide blisters, which was not observed in the Ca-added alloy. The presence of an Al4Ca phase at the grain boundaries led to the formation of multi-element oxides containing Al, Mg, and Ca, which can contribute to the formation of a compact oxide layer.

In this study, the solid and liquid oxidation behaviors of Al–Mg alloys that had a trace of Ca were investigated. With increasing Ca content, the grains of α-Al dendrites in Al–7.5mass%Mg alloys were refined by the formation of two Ca-containing particles at grain boundaries. Using thermal gravimetric analysis result at 515 °C for 24 h under O2 atmosphere, Al–7.5mass%Mg alloy exhibited a parabolic behavior in its weight gain during oxidation. However, there was nearly no difference in the weight change during oxidation of the Al–7.5mass%Mg alloys that contained a trace of Ca. From the auger electron spectroscopy and transmission electron microscopy/energy-dispersive X-ray spectroscopy results for the oxidized surface, it is believed that the improvement in the oxidation resistance in Al–7.5mass%Mg alloys that contain Ca may be attributed to the formation of a mixed oxide layer that includes CaO, MgO, and Al2O3 on the surface. After a melt holding test for 3 h, there was no notable difference in Mg loss during oxidation between Al–7.5mass%Mg and Al–7.5mass%Mg–0.1mass%Ca alloys. However, for a melt oxidation time for 24 h, the Mg reduction of Al–7.5mass%Mg alloy reached approximately 15%, whereas in Ca added alloy, the reduction was controlled under 8%. The cross section of Al–10mass%Mg alloy that solidified after the melt holding test showed a significant contamination due to oxide inclusions. However, Ca added alloys had good internal soundness throughout all the conditions. It was confirmed that the protective layer formed by Ca-containing can suppress the formation of Mg-based oxide inclusions and result in an increase in the alloy internal soundness during the melting process.

The effect of pre-aging treatment before extrusion has been investigated in Mg–9.0Al–1.0Zn–1MM–0.7CaO–0.3Mn alloy. The as-cast microstructure consists of α-Mg dendrite with secondary solidification phase particles, (Mg, Al)2Ca, β-Mg17Al12 and Al11RE3 at the inter-dendritic region. After extrusion, β-Mg17Al12 precipitates are present, but higher density and more homogeneous distribution in pre-aged alloy. In addition, μm-scale banded bulk β-Mg17Al12 particles are generated during extrusion. Al11RE3 particles are broken into small particles, and are aligned along the extrusion direction. (Mg, Al)2Ca particles are only slightly elongated along the extrusion direction, providing stronger particle stimulated nucleation (PSN) effect by severe deformation during extrusion. The mechanical properties can be significantly enhanced by introducing pre-aging treatment, i.e. β-Mg17Al12 precipitates provide grain refining and strengthening effects and (Mg, Al)2Ca particles provide PSN effect.

The effect of the volume fraction (0.6–8.4 vol %) of the icosahedral phase ( I -phase, Mg 3 Zn 6 Y 1 ) on the microstructure, hot deformation mechanism and hot workability of cast Mg-Y-Zn alloys was studied. As the volume fraction of I -phase increased, the fraction of dynamically recrystallized (DRXed) grains increased, indicating that I -phase promoted dynamic recrystallization (DRX) by providing the preferred nucleation sites for DRXed grains through particle stimulated nucleation mechanism. There was, however, a critical amount of I -phase (about 5 vol %) beyond which the fraction of DRXed grains decreased. This was attributed to the formation of relatively coarse divorced eutectic I -phase and lamellar I -phase structures at the volume fraction of I -phase ≥5%. This result indicates that besides the amount of I -phase, the size of I -phase structure is another important factor affecting DRX. Processing maps were constructured to evaluate the hot workability of the alloys with different volume fraction of I -phase. The hot workability increased as the volume fraction of I -phase increased up to about 5 vol % but decreased afterward, confirming that DRX and hot workability are correlated with each other. The hot workability increases with increasing I- phase amount because the occurrence of extensive DRX delays the onset of power-law breakdown and flow instability to higher strain rates and lower temperatures.

Using transmission electron microscopy (TEM) we studied the oxidation behaviors of CaO added Mg-3.5Al-1.4Zn (AZ31) alloys as a function of the CaO content and oxidation time, at 500 °C in air. It was shown that the AZ31 alloys with CaO exhibit substantially enhanced oxidation resistance. We identified the mechanism for this behavior: with added CaO the AZ31 alloys form protective oxide layers consisting of inner columnar and outer Ca/Mg rich structures. The thicknesses of the protective layers were observed and found to be correlated with the CaO content. The inner columnar layer grows along the [100] MgO due to the small energy barrier to the diffusion of interstitial oxygen ions in MgO. We observed three distinctive steps during the oxidation reaction: the formation of oxide islands, the dissipation of scale and the growth of a columnar oxide layer, and the formation of a double oxide layer due to Ca reduced from CaO. We clearly captured the microstructural evolution of the three different steps, leading to a detailed description of the formation of the protective oxide layers.

This paper deals with a robust $H$ ∞ tracking control problem for 3- R link robotic manipulator in Takagi-Sugeno fuzzy form. We focus on tracking control problem that is treated as stabilization problem and designing a fuzzy controller. The fuzzy controller in state feed-back form and feed-forward controller are taken into consideration and its design condition is derived in terms of linear matrix inequality. A numerical simulation is included to show the effectiveness of the theoretical development.

We present the synthesis of a bulk nanostructured Mg-based alloy that has a grain size less than 300 nm. A nanostructured Mg-Zn-Cu-Nd alloy with an exceptionally high hardness can be obtained through simultaneous consolidation and in situ crystallization of the amorphous Mg84Zn7Cu3Nd6 alloy precursor using the spark plasma sintering process. We evaluate the relationship between the microstructure and preparation conditions on the grain size of nanostructured Mg-based alloys during the sintering process. The hardness of the bulk sample produced from the sintered amorphous Mg-Zn-Cu-Nd precursor at 260 °C is maximized via the nanocrystallization of intermetallic compounds using the sintering process. The populated crystallization and confined growth of phases contribute to the refinement of gains in nanostructured Mg-based alloys.

The thermal conductivities of quaternary Mg-Zn-Ca-MM alloys have been investigated by evaluating the effect of MM on Mg-4Zn-0.5Ca alloys, with an emphasis to develop a new Mg alloy without compromising thermal conductivity, process-ability and mechanical property. As a result, the thermal conductivity of 0.5 wt.% MM-added Mg-Zn-Ca alloy was almost same as that of MM-free Mg-Zn-Ca alloy. However, with further increasing MM contents, thermal conductivities of MM-added alloys decreased. The tensile yield strength was improved with increasing MM contents. In addition, the average spiral flow lengths of Mg-Zn-Ca-xMM alloys were almost same levels with Mg-Zn-Ca alloy.