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The oxidation behaviors of molten WE43 (Mg-4.32Y-2.83Nd-0.41Zr, wt%) in resin-sand mold atmosphere were systematically investigated. X-ray diffraction, X-ray photoelectron spectroscopy, and scanning electron microscopy analyses were employed to identify the phase compositions and microstructures of surface oxide scale. The initial oxide scale characterized by a three-layer structure mainly consisted of MgO, Y2O3, and ZrO2 and then transformed to Y2O3 layers covered by porous MgO after holding at high temperatures. CALPHAD method was used to analyze the oxidation process, and the calculated phase diagrams agreed well with the experimental results. A selective oxidation model was established based on thermodynamic and kinetic analysis to describe the structure transformation of oxide scale in detail. The initial oxidation was controlled by inward diffusion of oxygen due to the protection of surface Y2O3. However, the oxide scale was not protective after long-term oxidation or at temperatures higher than 1073 K due to the oxide fracture, which can be attributed to the increase in stress caused by inner Y2O3 layer growth. Based on experimental results, the oxide growth stress parameter C was estimated to be 0.0013 and 0.0026 for 1023 and 973 K, respectively. This work reveals the underlying oxide growth and fracture mechanisms of molten Mg-Y alloy in mold, and provides guidance for preventing the ignition of magnesium alloys during casting processes. [ABSTRACT FROM AUTHOR]

In this research, precipitation evolution and strengthening behavior in Mg-3Nd-0.2Zn alloy during isothermal age treatment at 200 °C are quantitatively studied by a combination of experimental investigation and computational simulation. Microstructure evolution, including volume fraction, number density, and size of precipitates are first measured by TEM and DSC techniques and then modeled using an integrated computational simulation method combining the CALPHAD (CALculation of PHAse Diagram) approach and classical nucleation model. The focus of the analysis is set on the evolution of key strengthening precipitate β’. Critical kinetic parameters such as particle interfacial energy and nucleation site number are obtained computationally by fitting the model to the experimental data. Mechanical properties of a series of Mg-Nd-Zn alloys are predicted using the simulated microstructure evolution as inputs. Good agreement is found between simulated and measured results. Strategies for enhancing the precipitation hardening effect are presented and discussed based on the simulation results. The merit of this study is to use the obtained parameters to extrapolate microstructure evolution and mechanical properties when adjusting alloy composition and/or heat treatment conditions within a certain range, which will be very useful for further development and optimization of multi-component Mg alloys. [ABSTRACT FROM AUTHOR]

The 6xxx series wrought aluminum alloys (Al-Mg-Si-Cu) provide good formability and high strength potential, especially with high Cu additions. However, the large freezing ranges of these alloys often cause hot cracking susceptibility in solidification-based processes, such as casting, welding, and 3D printing. In this work, nano-treating, which is to tune the manufacturability and microstructure of metals by a small addition of nanoparticles, was applied to Al-Mg-Si-Cu alloys during casting. This study shows that nano-treating can effectively refine microstructure, eliminate hot cracking, and promote the dissolution of alloying elements. Tensile tests showed that nanoparticles enable strengthening. An extensive study on the TiC nanoparticle effect on Al-Mg-Si-Cu with various Mg and Si contents was conducted. This work provides valuable insights for rational design of nano-treated Al-Mg-Si-Cu alloys to achieve optimal combination of strength and ductility. • Difficult-to-cast Al-Mg-Si-Cu alloys have been successfully cast when treated with a low volume fraction of dispersed TiC nanoparticles. • TiC nanoparticles refined grain structures and precipitates in the nano-treated samples. • The nano-treated samples exhibit superior mechanical properties compared to their pure alloy counterparts under as-cast and T6 conditions. • TiC nanoparticles effects on Al-Mg-Si-Cu systems with different Si and Mg contents have been studied to optimize mechanical properties. [ABSTRACT FROM AUTHOR]

In the paper, conductive atomic force microscopy (CAFM) technique was used, for the first time, to obtain direct evidence of oxide-film removal during fluxing, via measuring the electrical conductivity of aluminum sample surfaces. The CAFM results show that the F − ions from the flux loosened the film, forming micro cracks on the oxide film. Subsequently, the Zn 2 + ions permeated into the film through the cracks and chemically reacted with the aluminum substrate, destroying the bonding between the oxide layer and the aluminum substrate. These important findings pave the way for developing Cl-free environment-friendly fluxes for industrial applications. [ABSTRACT FROM AUTHOR]

This paper presents a phase field model for describing microstructure and microsegregation in pressurized solidification of a ternary magnesium alloy, which captured essential physics associated with pressurized solidification of multi-component system, including pressure-effect-embedded thermodynamic modeling (PEE thermodynamic modeling) and interactive diffusion. This model was applied to squeeze casting of a Mg-Al-Sn alloy and revealed that the applied pressure increased solute trapping and solute accumulation in front of solid/liquid interface, which are two opposite factors contributing to microsegregation. Governed by the mechanism, the microsegregation of solute Al aggravates with applied pressure considerably, while that of Sn is rarely influenced by the pressure. [ABSTRACT FROM AUTHOR]

The increased use of lightweight aluminum die castings in the automotive industry leads to new die casting alloys and their heat treatment processes to meet performance requirements. In this paper, an integrated precipitation and strengthening framework based on an improved Kampmann-Wagner numerical (KWN) model was developed to predict the hardness and yield strength (YS) of high pressure die casting (HPDC) Al–11Si-xMg (x = 0.3 and 0.6) alloys during T5 aging (artificial aging after casting) process. The hardness and YS of the alloys were measured and compared with the predication results, for T5 treatment at 190 °C, 210 °C, 225 °C and 240 °C, respectively. The increased Mg content (from 0.3 to 0.6%) leads to the formation of Mg 2 Si phase during solidification, which effectively increases the hardness and YS in as-cast conditions. Also, the higher Mg content results in increased peak strengths because of higher precipitate density of needle-like Mg 5 Si 6 - β ″ phase. This improved KWN model showed a good accuracy with experimental results. Mechanical property maps were generated to guide the design and optimization of T5 process window for these two important die casting aluminum alloys. • An improved Kampmann-Wager numerical (KWN) precipitation model for Al–11Si-xMg alloys during T5 artificial aging treatment. • An integrated strengthening and precipitation model predicting hardness and yield strength validated by experimental results. • Mechanical property maps generated for design and optimization of T5 process for Al–11Si-xMg alloys. [ABSTRACT FROM AUTHOR]

Single pass large strain electroplastic rolling (LSER) was conducted on AZ31 alloy, using pulsed electric current of different current densities, to improve the rollability of magnesium alloy sheet. It was found that TD (transverse direction)-split texture developed in the alloy once the current density exceeded a critical value (in the present case 90 A/mm 2 ). Microstructure and texture analysis reveal that deformed grains, rather than the dynamically recrystallized grains, are the major contributor to the overall TD-split texture. Intragranular misorientation axis (IGMA) and viscoplastic self-consistent (VPSC) modeling were employed to analyze the influence of the pulsed electric current on the deformation mechanisms. Prismatic type geometrically necessary dislocations (GNDs) were found to be dominant in the deformed grains of the specimens with TD-split texture. VPSC modeling indicates that the TD-split texture is likely due to the enhanced prismatic activity caused by the electric current. The special athermal effect of the pulsed electric current on the deformation mechanisms makes LSER a promising technique for texture modification in magnesium alloys for improved formability. [ABSTRACT FROM AUTHOR]

Redistribution of impurities during the dissolution of AZ91 and synthesized Mg-0.5Cu alloys were studied with rotating ring-disk collection experiments and stripping voltammetry. In solution, where the potential value of both alloys is far below the equilibrium potential values of Cu oxidation reactions, nonfaradic release of Cu particles led to the production of Cu ions which were subsequently reductively collected on an outer Pt ring. The collected Cu was analyzed and confirmed with stripping voltammetry. The results of this work support the notion that isolated Cu atoms or Cu-rich particles can be oxided in aerated solutions at low potential values, and generated Cu ions can be reductively redeposited on a Mg alloy surface. [ABSTRACT FROM AUTHOR]

Poor plasticity at room temperature has been an acute challenge for the wrought magnesium alloys. Herein, we developed a dilute Mg-0.5Mn-0.1Al alloy with exceptional rollability (80% single-pass rolling reduction) and high ductility (56.3% tensile elongation) at room temperature. A fine grain structure with grains around 1 μm was obtained and a work softening behavior was observed. This exceptional rollability results from the dislocation annihilation at grain boundary and the occurrence of dynamic recrystallization (DRX) during deformation process at room temperature. The occurrence of DRX behavior at room temperature can be deviated into three stages: (1) activation of grain rotation, (2) initiation of grain boundary slip and non-basal plane slip, (3) the formation and of low angle grain boundaries and the immigration of grain boundaries. • A dilute Mg-0.5Mn-0.1Al alloy exhibits a high ductility with 56.3% at room temperature. • The high ductility Mg-0.5Mn-0.1Al alloy performs an exceptional cold rollability withstand 80% single-pass reduction. • The exceptional cold rollability is mainly related to the grain boundary slip and work soften. [ABSTRACT FROM AUTHOR]

The natural oxide layer is an inherent barrier in interfacial bonding between aluminium (Al) and magnesium (Mg) alloys in Mg/Al bimetallic casting, resulting in insufficient wettability between the molten Mg and solid Al substrate during bimetallic casting processes. In this investigation, a ‘zincate + nickelling’ surface treatment has been developed for Al alloy 6061 substrate, replacing the oxide layer with a nickel coating. This procedure comprises a combined pickling/redox-reaction and nickelling process, which drastically improves the substrate’s wettability with molten Mg. The bimetallic experiments conducted on a self-designed high-vacuum test apparatus provide valuable understanding of the interfacial phenomena of Mg/Al bimetallic castings. The test results show that the shear strength of bimetallic castings is significantly improved due to the fact that the formation of Mg–Al intermetallic compounds is impeded by a nickel coating. The potential corrosion problem associated with nickel additions could be addressed by an organic top coating for the bimetallic system. [ABSTRACT FROM PUBLISHER]

Microscopic deformation compatibility is a key in achieving high ductility in polycrystalline magnesium alloys. This paper presents a grain-level compatibility investigation of Mg-Gd-Y alloy using in-situ tension in scanning electron microscopy (SEM) combined with electron back scattered diffraction (EBSD) and digital image correlation (DIC) techniques. The results show that strain amplitudes are not always higher in grains with high Schmid factors of basal slip. Thus, the Schmid law can hardly predict the strain amplitudes at grain level. In addition, the average intergranular strains are higher than the average intragranular strain and a strong surrounding effect grain-to-grain was found. A slip-transfer parameter m′ , describing the surrounding effect, was used to evaluate the deformation compatibility. It is found that a high m′ value and a high Schmid factor of certain slip system in the adjacent grains would result in a good compatibility around grain boundaries and could accommodate higher local strains, which would improve the ductility of magnesium alloys. [ABSTRACT FROM AUTHOR]

The solidification microstructures of AE42 (Mg-4Al-2RE, wt%) alloys with three different cooling rates are investigated using CALculation of PHase Diagrams (CALPHAD) simulation and experimental validation. The results show that high cooling rates can refine the microstructure and decrease the formation of particulate AlRE intermetallics. Particularly, the MgAl phase, predicted by CALPHAD simulation using the Scheil model, is not observed in the high-pressure die casting (HPDC) sample. The suppression of MgAl in HPDC AE42 alloy at high cooling rates and high pressure is likely due to the supersaturation of Al in (Mg), in addition to the preferential formation of AlRE and AlRE phases. [ABSTRACT FROM AUTHOR]

Experiments were designed to compare the rollability of magnesium alloy AZ31 sheet in two rolling schedules at the same rolling temperatures: multi-pass electroplastic rolling (ER) and warm rolling (WR). While cracks occur in WR sheet at an accumulative true strain of − 0.24, the sheet can be rolled by ER up to an accumulative true strain of − 1.09 without edge-cracking. This rollability enhancement in ER sheet was found to be related to the improved homogeneity of plastic deformation and dynamic recrystallization (DRX), which postpones the crack initiation. A ‘twinning - shear banding - DRX’ microstructure evolution model was proposed to explain the effect of pulsed electric current on the homogeneity of deformation and subsequent DRX. The use of ER sheet could pave the way for low-cost applications of lightweight magnesium components. [ABSTRACT FROM AUTHOR]

Electroplastic rolling (ER) and conventional warm rolling (WR) were conducted on Mg–3Al–1Zn (AZ31) sheet to study, for the first time, the influence of pulsed electric current on the twinning behavior of magnesium alloy. The 10 1 ̅ 2 extension twins were found insensitive to the current. The primary 10 1 ̅ 1 contraction twins, in contrast, display higher number fraction of twinned grains and better Schmid behavior in ER than in WR. This difference indicates a special ‘athermal’ influence of the current, which probably originates from the improved strain accommodation due to enhanced prismatic < a > activity. The distinctive twinning behavior is related to the improved rollability. [ABSTRACT FROM AUTHOR]

Ordered-segregated Gd atoms in coherent twin boundaries (CTBs) improve the strength of Mg–Gd alloys after annealing. Here we show a new kind of incoherent twin boundary (ITB) with Gd segregation after annealing in a Mg–3Gd alloy. This new ITB (ITB') does not lie on 10 1 ¯ 2 twinning plane, nor is it parallel to [ 1 2 ¯ 10 ]. The thick morphology of this ITB' is due to twinning plane rotation around [0001] Twin by uncertain angles (~ 7° and ~ 13° observed). The ITB', driven by dislocation rearrangement in the boundary and total system energy reduction, is supposed to have higher strengthening effect than normal ITB and CTB. [ABSTRACT FROM AUTHOR]

Three-point bending represents important straining in metal forming, and is an ideal loading condition for in-situ investigation of complex microstructure evolution and plasticity of magnesium alloys. Two extruded alloys with different initial texture, AZ31 (Mg–3%Al–0.5%Zn 1 ) and AM30 (Mg–3%Al–0.3%Mn), were studied in three-point bending with in-situ electron backscatter diffraction (EBSD) observations, to reveal the role of strain gradient and deformation compatibility in the plasticity of magnesium alloys. The results indicate that strain gradients in macro-scale from tension to compression can lead to a graded microstructure and texture evolution in the samples during bending. At the intergranular and intragranular levels, the volume fraction of twins was influenced by the slip-induced twinning behavior and strain compatibility among the surrounding grains except for Schmid factor relating to grain orientation. Slip-induced twinning behavior and its surrounding effects on the twinning volume fraction is much more profound in materials with weak textures. The AM30 alloy with a weaker texture shows better deformation compatibility (and, thus, formability) during three-point bending compared to AZ31 alloy with a stronger texture in this study. [ABSTRACT FROM AUTHOR]

Highlights: [•] Ternary phases in Mg–Zn–Sm alloy system were experimentally determined. [•] One previously-reported ternary phase is determined as Mg3Sm binary phase. [•] Phase relationships of Mg–Zn–Sm system near Mg corner are obtained experimentally. [•] A thermodynamic description of this system was developed using CALPHAD method. [ABSTRACT FROM AUTHOR]

• HEA particles successfully dispersed into molten aluminum via ultrasonic processing. • HEA particles reacted with molten aluminum forming new intermetallic phases. • Aluminum matrix significantly strengthened by in-situ formed intermetallic phases. • Matrix/particle interfacial reactions critical in metal matrix composite processing. [Display omitted] The feasibility of adding AlCrTiV high entropy alloy (HEA) particles to molten aluminum to make metal matrix composites was studied. Equiatomic AlCrTiV HEA particles, produced by a solid state reduction process, were dispersed into pure aluminum and 7075 alloy (Al-5.8Zn-2.3Mg-1.4Cu, all weight %) melt and by a ultrasonic dispenser. It was found that the AlCrTiV particles reacted with molten aluminum, leading to the formation of Al 45 (Cr,V) 7 and Al 3 Ti intermetallic phases in the aluminum matrix composites. Although the AlCrTiV HEA particles did not survive in molten aluminum during composite processing, the final composite materials showed significantly improved mechanical properties, due to grain refinement and dispersion strengthening. The research suggests that the interactions between matrix aluminum alloys and the particles are key in controlling the final microstructure and properties of the composites. [ABSTRACT FROM AUTHOR]

Abstract: The fatigue properties of an extruded Mg–3Al–0Mn magnesium alloy component were evaluated experimentally. Fully reversed, strain control fatigue tests were conducted on specimens extracted from regions with a varying grain size and texture. Scanning electron microscopy was employed to establish structure–property relations between microstructure and cyclic damage. Relations were drawn between microstructural features such as particle size, grain size, initial Taylor factor and the number of cycles to failure. [Copyright &y& Elsevier]

Abstract: Magnesium alloys are increasingly used in automotive and aerospace industries for weight reduction and fuel economy improvement. Low cycle fatigue (LCF) behavior of these alloys is an important consideration for the structural applications. The objective of the present investigation was to identify influences of strain ratio and strain rate on cyclic deformation characteristics and fatigue life of an AZ31 extruded alloy. As the strain ratio decreased, stronger cyclic hardening rate, more asymmetric hysteresis loop, smaller stress amplitude, lower mean stress, and higher initial plastic strain amplitude were observed due to increasing compressive stresses. This was considered to be associated with the twinning during cyclic deformation in the compressive phase, and detwinning in the tensile phase. The residual twins acting as barriers to dislocation slip and pile-up were considered to be the main cause for the occurrence of cyclic hardening. Fatigue life increased with decreasing strain ratio and increasing strain rate. Fatigue crack initiation occurred at the specimen surface due to the presence of larger grains near the surface, and fatigue crack propagation was characterized by a mixture of striations and dimple-like ductile fracture features. [Copyright &y& Elsevier]

Abstract: Lightweight magnesium alloys are being increasingly used in automotive and other transportation industries to achieve energy efficiency and environmental protection. Design of magnesium components requires low cycle fatigue (LCF) behavior since these applications are often subjected to cyclic loading and/or thermal stresses. The objective of this investigation was to study the cyclic deformation behavior and LCF life of a large solid extruded section of AZ31 magnesium alloy. It was observed that the alloy was cyclically stable at lower strain amplitudes and exhibited cyclic hardening characteristics at higher strain amplitudes, with a cyclic hardening exponent of about 2.6 times higher than the monotonic strain hardening exponent. A relationship between the plastic strain amplitude and the number of cycles (N), was observed. With increasing total strain amplitude both plastic strain amplitude and mean stress increased and the fatigue lifetime decreased. Bauschinger effect was pronounced at higher strain amplitudes, resulting in asymmetric hysteresis loops due to twinning in compression during unloading and subsequent detwinning in tension during loading. Modulus during cyclic deformation was constant at the low strain amplitude, but it decreased with increasing strain amplitudes and increased with increasing number of cycles at the high strain amplitudes due to the presence of pseudoelastic behavior. Fatigue parameters following the Coffin-Manson and Basquin’s equations were evaluated. Fatigue crack initiation was observed to occur from the specimen surface and crack propagation was characterized by striation-like features coupled with secondary cracks. [Copyright &y& Elsevier]

This paper describes a significant increase in elongation in Mg due to the addition of only 0.2% Ce. This effect is explained as due to the Ce addition altering the texture of the extruded rods during recrystallization by orienting the c-axis of the grains at an angle that favors basal slip activity. A concomitant reduction in grain size and yield strength and an increase in work hardening rate are also observed as a result of the Ce addition. [Copyright &y& Elsevier]

Abstract: The influences of temperature, bending velocity and original grain size on the bendability of tubes have been investigated. The cross-section ovality and released spring back rate decrease with increasing temperature, while the maximum wall-thinning rate reaches the minimum at the moderate temperature. With increasing bending velocity, the wall-thinning rate and ovality increase, while the change of spring back rate exhibits an opposite trend. In addition, the wall-thinning rate, ovality and spring back rate increase with the accretion of original grain size. The results suggest moderate temperature, lower bending velocity and small original grain size are beneficial to the reduction of maximum wall-thinning rate, cross-section ovality and released spring back rate. [Copyright &y& Elsevier]

Abstract: In this paper, a combined experimental and numerical investigation of free hydroforming of aluminium alloy tubes is conducted. The tubes are subjected to different loading histories involving axial compression and internal pressure. The circumferential and axial strains experienced by the tubes are continuously recorded along with the pressure and axial load. The numerical simulations are carried out using both 2D axisymmetric and 3D finite-element formulations by applying the experimentally recorded axial load and internal pressure. In the latter, a geometric imperfection is introduced in the form of wall thickness reduction at the tube mid-length in order to trigger necking which happens after significant bulging and beyond the stage of peak pressure. The strain histories and peak pressures obtained from the simulations agree well with those determined from the experiments. Further, the forming limit curve predicted by the simulations as well as from a M–K analysis incorporating the computed strain paths corroborate well with the experimental data. The role of nonproportional straining on the mechanics of failure of the tubes due to bulging and necking is studied in detail. [Copyright &y& Elsevier]

A newly developed Mg–2Zn-0.3Ca-0.2Ce-0.1Mn (in weight %, ZXEM2000) wrought alloy exhibits an exceptionally high tensile ductility (29% ± 1.4% tensile elongation) along the rolling direction at room temperature. In this work, we investigated the fundamental plastic deformation mechanisms that can contribute to the high ductility of ZXEM2000. Scanning electron microscopy and transmission electron microscopy were carried out at selected strain levels to characterize the microstructural evolution. Compared with the deformed microstructures from the hot-rolled pure Mg and Mg–3Al–1Zn alloy at similar conditions, our results revealed that the high ductility of ZXEM2000 could be attributed to four key factors: weaker texture, fine grain size, reduced twinning, and increased cross-slip frequency of dislocation. These direct observations offer a key insight into improving ductility of magnesium alloys for future alloy design and development. [ABSTRACT FROM AUTHOR]

Strain-controlled fatigue tests were performed on a cast Mg–8Gd–3Y–0.5Zr (wt. %, GW83K) alloy to investigate the effect of microstructure on strain localization and fatigue crack initiation. The results show that, in T4 alloys, a large number of basal slips in individual grains and most grains in the bulk material are involved in plastic deformation and fatigue damage because persistent slip bands (PSBs) are dense and uniform. The interaction between dense PSBs and grain boundaries (GBs) occurs continuously along a wide range of GBs, resulting in uniform distribution of residual strains along GBs. The grain-level strain localizations within and among grains are effectively alleviated. In T6 alloys, however, due to the sparse and inhomogeneous PSBs, only a few basal slips in individual grains and only a few grains in the bulk material participate in plastic deformation and fatigue damage. The interaction sites between sparse PSBs and GBs is significantly limited, which leads to highly concentrated deformation at a few specific areas of the GBs. It results in high trans -granular strain localization in long range stretching across both grain interiors and GBs in short cycles. The strain localizations within and among grains are relatively aggravated. Moreover, the saturated strains of the T4 alloys are much larger than those of the T6 alloys. Therefore, under the same loading condition, it takes more cycles for T4 alloys, while fewer cycles for T6 alloys, to reach the saturation strains and initiate micro-cracks. In other words, the crack initiation life of T4 alloys is much longer than that of T6 alloys. • The grain-level strain localization is characterized via micro-DIC. • The saturated strain of T4 alloys are much higher than that of T6 alloys. • Sparse PSBs mode in T6 alloys result in higher strain localization level. • The T6 alloys reach saturated strain earlier due to strong strain localizations. • Aggravated fatigue damage help shortening the crack initiation life of T6 alloys. [ABSTRACT FROM AUTHOR]

• A new 3-D CA multi-component model is developed to predict microstructure and microsegregation during solidification processing. • The effect of solute interactions on diffusion and competitive growth is quantitatively revealed for the first time. • Thermodynamic and kinetic parameters of multi-component system can be obtained from CALPHAD calculations for CA modeling. • The effect of cooling rate on SDAS has been analyzed and compared with experimental results and literature data. • The new model has been validated by a well-accepted analytic model and directional solidification experiments. A multi-component model was developed to simulate microstructure evolution during solidification of a quinary alloy system. The thermodynamic and kinetic parameters including liquidus slope, partitioning coefficient, diffusion coefficient etc. as functions of temperature and solute concentration were obtained using CALculation of PHAse Diagrams (CALPHAD) modeling. The effect of solute interactions on diffusion and dendrite growth velocity was fully considered in this model. The model was validated by mesh size convergence, and compared with a well-accepted analytical model. The new model was shown to successfully display solidification dendrites and solute redistributions of a quinary Al-Si-Mg-Fe-Mn alloy. The effect of different solute elements on solute diffusion and dendrite growth was analyzed. Additionally, various calculation domains and cooling rates of industrial importance were tested in the simulations. Directional solidification experiments were used for model validation in secondary dendrite arm spacing measurement and simulation. The validated relationship between the secondary dendrite arm spacing and cooling rate in a complex quinary system confirmed the accuracy of this 3-D multi-component model, which provides a critical connection between solidification processing and mechanical property prediction in Integrated Computational Materials Engineering (ICME) of solidification products. [ABSTRACT FROM AUTHOR]

Predicting location specific properties of industrial castings is a critical part of the Integrated Computational Materials Engineering (ICME) framework for casting design and manufacturing. In this paper, a new design methodology is presented to calculate and predict location specific mechanical properties of an aluminum casting based on its location specific microstructure. Cellular Automaton (CA) and Finite Element Analysis (FEA) tools are coupled to model the mechanical response of a cast component from the casting process conditions to its final location specific solidification microstructure. This new CA-FEA methodology can bridge multiple length scales and predict location specific microstructure and mechanical properties of an aluminum wedge casting, which was experimentally validated using X-ray Micro Computed Tomography and mechanical testing. Unlabelled Image • CA-FEA approach couples multiple CAE tools to calculate the non-uniform development of location specific microstructures. • CA-FEA approach links multiple length-scales with limited to no loss in microstructural features including morphology/size. • The CA-FEA approach is immensely useful during the design of complex components that experience various loading conditions. • Utilization of the CA-FEA approach greatly reduces scrap quantity, while also improving the quality of the casting. • CA-FEA method was experimentally validated and accurately predicted mechanical properties at a previously unattainable level. [ABSTRACT FROM AUTHOR]

The tensile elongation of high-pressure die casting Mg-4Ce-xAl-0.5Mn alloy was significantly improved from 1% to 14% when the Al content was increased from 0 wt% to 3 wt%. Microstructural characterization and fractographic analyses were carried out to reveal the mechanism of ductility enhancement. With increasing Al content, the intermetallic particles evolve from the network-like Mg 12 Ce to fine acicular Al 11 Ce 3 with a few small blocky Al 2 Ce and Al 10 Ce 2 Mn 7 and to coarse Al 11 Ce 3 , large blocky Al 2 Ce and Al 10 Ce 2 Mn 7. The network-like Mg 12 Ce, large and elongated Al 2 Ce and Al 10 Ce 2 Mn 7 particles show the great tendency to cracking, while cracking of the small blocky Al 2 Ce and Al 10 Ce 2 Mn 7 particles or fine acicular Al 11 Ce 3 particles is relatively lag. In Mg-4Ce-0.5Mn alloy, microcracks propagate rapidly along the cracked Mg 12 Ce particles in the intergranular area. However, both the microcracks in Mg-4Ce-3Al-0.5Mn and Mg-4Ce-6Al-0.5Mn alloys need to penetrate into the grains to grow and coalesce together, which occurs only after certain plastic strain accumulating inside the grains. [ABSTRACT FROM AUTHOR]

Mg and its alloys possess a biodegradable nature that has recently made them attractive for potential applications in biomedical devices that are expected to degrade and bioresorb completely in-vivo after the healing of the body tissue. We have developed an Mg-Zn-Ca-Mn alloy containing biocompatible alloying elements, and a heat treatment process that is likely to improve mechanical stability and absorption properties during bone healing and reliably resorb following the healing of a reconstructed skeletal segment. Our objective in this work is to investigate the use of a composite ceramic-based coating to delay the degradation (weakening) of our strengthened alloy for several months to avoid loss of mechanical properties during the healing process. The heat-treated alloy samples were coated using plasma electrolytic oxidation (PEO) and a sol-gel (layer-by-layer) coating techniques to achieve improved corrosion resistance. The coated samples were characterized for their morphological and corrosion characteristics using scanning electron microscope (SEM), X-ray diffraction analysis (XRD), and in vitro corrosion testing methods. These in vitro corrosion studies showed a significant improvement in the corrosion resistance of the PEO/sol-gel coated alloy. The PEO/sol-gel coated alloy samples lost only approx. 3% of their strength, after 8 weeks of immersion in a corrosive environment, compared to 30% loss for the uncoated alloy samples under the same conditions. The results of this study suggest that it should be possible to maintain the mechanical integrity of Mg-based implants inside the body for the desired 6–9 month period and longer if that becomes useful. • Sol-gel coating was created on heat-treated Mg alloy without the need for sintering. • Biphasic ceramic nanoparticles were successfully incorporated in the sol-gel coting. • Sol-gel coating has corrosion rate 27 times less than Plasma electrolytic oxidation. • Sol-gel coated alloy showed approx. 3% loss of strength after 8 weeks of immersion. [ABSTRACT FROM AUTHOR]

Squeeze casting of biodegradable Mg-4Zn-0.5Ca-xMn (x = 0, 0.4 or 0.8 all in weight %) alloys is a process intended to improve mechanical properties (i.e., strength and ductility), corrosion performance (i.e., resistance), and biocompatibility (i.e., little to no cytotoxicity). In this study, we found that an increased Mn content causes the dendritic microstructure of squeeze-cast Mg-4Zn-0.5Ca-xMn to become more refined and uniform, while the volume fraction of the Ca 2 Mg 6 Zn 3 phase simultaneously increases. Squeeze-cast Mg-4Zn-0.5Ca-0.8Mn presents the best yield strength, ultimate tensile strength, and elongation of the alloys tested. An electrochemical corrosion test in Hanks' solution at 36.5°C demonstrates that the corrosion resistance of squeeze-cast Mg-4Zn-0.5Ca-xMn alloys show improvement at higher Mn levels. Additionally, squeeze-cast Mg-4Zn-0.5Ca alloys containing Mn exhibit favorable biocompatibility, as evidenced by cell viability studies with MC3T3-E1 cells and a local lymph node assay test. Squeeze-cast alloy specimens implanted into the skull and spine of Sprague-Dawley rats for four weeks showed no serious cytotoxicity or foreign body response; however, swelling was observed in the implantation areas of Mn-free squeeze-cast Mg-4Zn-0.5Ca alloy, while no swelling was observed in rats implanted with Mn-containing Mg-4Zn-0.5Ca alloy. These findings indicate potential applications of biodegradable, Mn-containing, squeeze-cast Mg-4Zn-0.5Ca specimens in bone-reconstruction devices given their biocompatibility, mechanical properties, and degradation profiles. STATEMENT OF SIGNIFICANCE: Bioresorbable magnesium alloys have recently gained attention as viable biomaterials for skeletal reconstruction implants. Extensive research on biodegradable Mg alloy design, synthesis, and as-cast versus post-processed material properties useful for medical applications have been reported. The squeeze-casting technique used in this study can improve the mechanical properties (i.e., strengthening) and corrosive performance (reduced rate) of bioresorbable Mg-Zn-Ca-Mn alloys. Squeeze-casting of these alloys is also expected to improve specimen microstructure, near-net-shape manufacturing, and cost (i.e., reduced). This study provides an in vitro and in vivo assessment of squeeze-cast Mg-Zn-Ca-Mn alloys for biomedical applications., Competing Interests: Declaration of Competing Interest The authors declare no conflict of interest associated with this article., (Copyright © 2022. Published by Elsevier Ltd.)

Mg-Zn-Ca alloys have grabbed most of the recent attention in research attempting to develop an Mg alloy for bone fixation devices due to their superior biocompatibility. However, early resorption and insufficient strength remain the main problems that hinder their use. Heat treatment has previously been thoroughly studied as a post-shaping process, especially after the fabrication of complex parts (e.g. porous structures) by 3D-printing or powder metallurgy. In this work, the effect of heat treatment on Mg-1.2Zn-0.5Ca (wt%) alloy's microstructural, mechanical and corrosion properties was studied. The surface morphology of samples was characterized by optical microscopy, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and x-ray diffraction (XRD). Hardness, compression and tensile tests were conducted, while the in vitro corrosion characteristics of the prepared samples were determined using potentiodynamic polarization (PDP) and immersion tests. It was found that increasing the age hardening duration up to 2-5h increased the heat-treated Mg-1.2Zn-0.5Ca alloy's mechanical properties. Further increase in the age hardening duration did not result in further enhancement in mechanical properties. Similarly, heat treatment significantly altered the Mg-1.2Zn-0.5Ca alloy's in vitro corrosion properties. The corrosion rate of the Mg-1.2Zn-0.5Ca alloy after the heat treatment process was reduced to half of that for the as-cast alloy. XRD results showed the formation of biocompatible agglomerations of hydroxyapatite (HA) and magnesium hydroxide (Mg(OH) 2 ) on the corroded surface of the heat-treated Mg-1.2Zn-0.5Ca alloy samples. The performed heat treatment process had a significant effect on both mechanical and corrosion properties of the prepared Mg-1.2Zn-0.5Ca alloy. The age hardening duration which caused the greatest increase in mechanical and the most slowed corrosion rate for Mg-1.2Zn-0.5Ca alloy material was between 2 and 5h., (Copyright © 2017 Elsevier Ltd. All rights reserved.)