Effect Of Scandium Addition Research Articles

Effect of Scandium Addition on Mechanical Properties and Microstructural Evolution in Al-Zn-Mg Alloys Processed through the Friction Stir Processing

Effect of Scandium Addition on Mechanical Properties and Microstructural Evolution in Al-Zn-Mg Alloys Processed through the Friction Stir Processing

Effect of scandium addition on microstructure and mechanical properties of as-cast Al-5%Cu alloys

Grain refinement is one of the effective methods to improve the yield strength and toughness of Al-Cu alloys. The effects of Sc addition (0.2%, 0.4%, 0.6%, 0.8% and 1.0 wt%) on the microstructural evolution and mechanical properties of as-cast Al-5%Cu alloys were studied. The as-cast samples were characterized by optical microscope (OM), transmission electron microscopy (TEM), scanning electron microscope (SEM) and electron probe microanalysis (EPMA). The results revealed the primary α-Al occurred to obvious change from developed dendrites to fine equiaxed grains with the increasing Sc content in Al-5%Cu alloy. When the addition concentration of Sc reaches 0.8%, the developed α-Al dendrites were significantly refined and the average size of α-Al decreased from 218.3 μm to 29.6 μm. Moreover, the morphology and size of θ-Al2Cu phases of Al-5%Cu alloy caused noticeable changes with the increase of Sc concentration. Mechanical properties test illustrated that the ultimate tensile strength (UTS), yield strength (YS) and elongation (El) increased by 61.59%, 66.82% and 57.20%, respectively, which could be attributed to microstructure refinement and fine Al3Sc particle precipitate.

Effect of Scandium Additions on the Temperature Dependences of the Heat Capacity and Thermodynamic Functions of Aluminum–Manganese Alloys

Abstract—The “cooling” method based on the Newton–Richmann law is used to measure specific heat capacity. It is shown that, as the manganese concentration in aluminum—magnesium alloys and temperature increase, the specific heat capacity of the alloys increases; as the scandium concentration increases, the heat capacity slightly decreases. As the temperature increases, the specific enthalpy and entropy of the alloys increase, whereas the specific Gibbs energy decreases. Scandium additions almost do not affect changes in thermodynamic functions of the alloys.

Effects of Scandium Addition on the Structural Stability and Ideal Strengths of Magnesium-Lithium Alloys

Abstract The effects of scandium (Sc) solute addition on the structural stability, mechanical strength, and electronic structure of magnesium-lithium (Mg-Li) ordered alloy were comprehensively studied by first-principles calculations. Two kinds of MgLi-Sc substitutional alloys (Mg-substituted Mg8−xLi8Scx and Li-substituted Mg8Li8−xScx) hold cubic lattice symmetry and become more stable with the increase in Sc content. The mechanical properties, including single crystal elastic constants, polycrystalline elastic moduli, and elastic anisotropy behaviors, have been systematically studied for two considered MgLi-Sc substitutional alloys. It was found that Mg8Li8−xScx exhibits larger elastic moduli than those of Mg8−xLi8Scx with the same Sc content; however, the derived elastic moduli of two substitutional alloys showed nonlinear variations as a function of Sc addition. Calculated stress–strain curves show an increasing of ideal tensile strengths and critical strains of the MgLi-Sc substitutional alloys along the <110> and <111> directions with Sc addition, indicating that the cubic MgLi-Sc substitutional alloy is mechanically harder and less brittle at higher Sc content. Furthermore, the developments of the electronic structures of two types of the studied alloys with increasing Sc addition were also investigated by the density of states and electronic localization function calculations.

Effects of scandium addition on biocompatibility of biodegradable Mg–1.5Zn–0.6Zr alloy

Heretofore, the effects of scandium on the biocompatibility of biodegradable magnesium alloys are extremely limited recognized. In the present study, four Mg–1.5Zn–0.6Zr–xSc (x = 0, 0.2, 0.5, 1.0 wt%) alloys were fabricated and their hydrophilicity, cytotoxicity, and hemocompatibility were investigated. The contact angle measurements revealed that addition of Sc improved the hydrophilicity of the alloys. For biodegradable alloys, perfect hydrophilicity could promote the tissue attaching on implant surface, establishing a benign biological reaction and improving the therapeutic effectiveness. The viabilities of L-929 cells and SP2/0 cells for all the alloys were about 100% and 90% compared to negative control, respectively. No obvious differences existed in cell viabilities between different Sc contents. With increasing addition of Sc, the hemolysis percentages and the degree of platelet activation increased. It deteriorated the hemocompatibility of the alloys. Proteomics, genomics, and in vivo investigations are needed in the future to get more deep understandings of the biocompatibility of Sc.

Effects of scandium addition on microstructure, mechanical and thermal properties of cast Be-Al alloy

The microstructure modification, mechanical property reinforcement, and thermal behaviors of arc-melted casting beryllium-aluminum (Be-Al) alloys with the addition of various contents of scandium (Sc) were studied in this work. The addition of 0.2wt% Sc shortened the secondary dendritic arm spacing (SDAS) of Be dendrites; the addition of 0.4wt% Sc further decreased the SDAS, weakened the dendritic structure of Be, and afforded equiaxed/cellular alloy microstructure with the finest Be grain size; however, higher additions of Sc till 3.0wt% enlarged the SDAS of Be and coarsened the Be grains. An explanation for the microstructure variation was proposed. The addition of Sc resulted in the formation of intermetallic compounds Be13Sc and Al3Sc distributed in the Be and Al matrices and along the Be/Al grain boundaries. It was observed that Sc preferentially formed Be13Sc and rendered the Be phase less plastic. The addition of Sc increased the hardness and elastic modulus of Be-Al alloys while strengthening the Be phase to a higher extent than Al. Thermal analysis showed that the Al phase had the highest latent heat of 167.6 J/g during melting and a low nucleation undercooling of 16.4 °C during solidification with the addition of 0.4wt% Sc. Heat treatment and water quenching changed the relative contents of Be13Sc and Al3Sc and further strengthened the alloys.

Effects of Scandium Addition and T7 Heat Treatment on Thermal Stability and Corrosion Properties of A201 Alloy

This study elucidates how scandium addition and T7 heat treatment affects thermal stability and corrosion properties of A201 alloy. The as-cast and the T7 heat-treated specimens were thermally exposed at 300 °C for 120 h to investigate the evolution of the Sc-free and the Sc-containing alloys. The results indicated that adding 0.6 wt.% scandium to A201 alloy could produce Al3Sc, W phase (Al8-5.4Cu6.6-4Sc) and grain refinement, significantly enhancing the hardness and tensile strength in as-cast condition. The as-cast A201 alloy containing Sc also showed the least loss of hardness and strength during thermal exposure at 300 °C. In addition, the presence of W phase weakened the peak hardness and tensile strength of the Sc-containing A201 alloy during T7 heat treatment. Adding Sc to A201 alloy increased corrosion resistance in T7 heat-treated condition, but slightly decreased corrosion resistance in as-cast condition.

Effect of Scandium addition on evolution of microstructure, texture and mechanical properties of thermo-mechanically processed Al-Li alloy AA2195

In the present study, influence of Scandium (Sc) content (0.025 and 0.25 wt%) on microstructure, texture and mechanical properties of a thermo-mechanically processed AA2195 alloy has been investigated. Addition of Sc to AA2195 alloy results in grain refinement and enhanced precipitation kinetics. TEM analysis revealed the presence of Al3(Sc,Zr) dispersoids in the Sc containing AA2195 alloys. Solution treatment and peak aging of the Sc containing alloys revealed partially recrystallized microstructure. Texture of Sc containing alloys displayed weaker Brass component compared to the Sc free material. A clear improvement in hardness and strength was observed which could be attributed to grain refinement as well as the presence of fine Al3(Sc,Zr) dispersoids. Ductility decreased slightly on Sc addition and there was an associated change in fracture mode as a result of Sc addition.

Effect of heat treatment on gravity die-cast Sc-A356 aluminium alloy

The effects of scandium addition (0.00 wt.%, 0.2 wt.%, 0.4 wt.% and 0.6 wt.%) and T6 heat treatment on the microstructure and mechanical properties of A356 aluminium alloy have been investigated in the research reported in this paper. The Sc inoculated specimens were prepared by gravity die-casting, according to ASTM B557-06 standard. The cast samples were then subjected to heat treatment at solutionizing temperature of 540 °C for 8 h followed by water quenching and artificial aging at 160 °C for 6 h. The microstructure, microhardness and tensile strength of the heat-treated samples were examined with use of scanning electron microscope (SEM), optical microscope, Vicker’s hardness tester, and Instron static machine respectively. Heat treatment was found to be able to effectively reduce grain size down to 16 μm (0.6 wt.% Sc), from 40 μm (original A356). The tensile strength was significantly improved, up to 338 MPa for heat treated 0.6 wt.% Sc-A356 having been achieved. The microhardness of 118 HV has been obtained for heat treated 0.6 wt.%Sc-A356.

The effect of scandium addition on microstructure and mechanical properties of Al–Si–Mg alloy: A multi-refinement modifier

Effect of scandium (Sc) additions on the microstructure, mechanical properties and fracture behavior of Al–Si–Mg casting alloy (F357) were systematically investigated. It was found that Sc addition caused a multi-refining efficiency on the microstructure of as-cast F357 alloy, including refinement of grains and secondary dendrite arm spacing (SDAS), modification of eutectic Si and harmless disposal of β-Al5FeSi phase. Subsequent T6 heat treatment had further induced the complete spheroidization of eutectic Si and precipitation of fine secondary Al3Sc dispersoids in the Sc modified alloys. Thus the mechanical properties, especially the ductility, were significantly enhanced by the addition of Sc combined with the heat treatment. The highest ultimate tensile strength, yield strength and elongation were achieved in 0.8wt.% Sc modified F357 alloy combined with T6 heat treatment. Furthermore, fractographic examinations indicated that the ductile fracture mechanism served as a dominate role in the modified alloys due to the formation of fine, deep and uniformly distributed dimples.

Effect of scandium addition on the microstructure, mechanical and wear properties of the spray formed hypereutectic aluminum–silicon alloys

Hypereutectic Al–x%Si–0.8Sc alloys (x=13, 16, 19 and 22wt%) were produced by spray forming. The microstructures of all the alloys exhibited very fine silicon phase with average size of about 5–10µm irrespective of the silicon content of the alloy. Transmission electron microscopy revealed the presence of a nano-scale scandium rich phase, identified as AlSi2Sc2 (V-phase) uniformly distributed in the alloy. The presence of V-phase resulted in higher matrix hardness (1.34GPa) in contrast to 1.04GPa observed in the case of binary Al–Si alloys by nanoindentation. Isothermal heat treatment at 375°C revealed insignificant coarsening of silicon phase in both binary and ternary alloys. The Al–x%Si–0.8Sc alloys exhibited higher flow stress and tensile strength in contrast to their binary alloy counterparts which was attributed to the bi-modal size distribution of the strengthening phases in the form of nano-scale V-phase and sub-micron to 10µm size silicon particles. The pin-on-disk wear tests exhibited appreciable improvement in the wear performance of the relatively low-silicon content ternary alloys over their binary counterparts while the high-silicon content binary and ternary alloys exhibited no much difference in the wear performance.

Effects of scandium addition on iron-bearing phases and tensile properties of Al–7Si–0.6Mg alloys

Iron is the most deleterious impurity in aluminum alloys and can easily combine with aluminum to form an acicular β-Al5FeSi phase that reduces ductility during the solidification of the molten metal. Adding scandium (Sc) to Al–7Si–0.6Mg alloys can transform the acicular β-Al5FeSi phase into a comparatively harmless nodular Sc–Fe phase (Al12Si6Fe2(Mg,Sc)5). This Sc–Fe phase has a lower hardness and elastic modulus than the β-Al5FeSi phase; it is thus less likely to initiate cracks in the Al matrix. Moreover, the nodular Sc–Fe phase can improve the fluidity of Al during solidification, reducing interdendritic shrinkage. Tensile testing measurements showed that the elongation of Al–7Si–0.6Mg alloys with 0.04 and 0.12wt% Sc can be respectively increased by 115% and 110% compared to Al–7Si–0.6Mg without Sc. The corresponding quality indices are increased by 17% and 19%, respectively, suggesting that the tensile properties of Al–7Si–0.6Mg alloys can be enhanced by adding scandium.

Effects of scandium addition on microstructure and mechanical properties of ZK60 alloy

AbstractThe effects of Sc addition on the microstructure and mechanical properties of the ZK60 wrought magnesium alloy were investigated by using optical microscope, scanning electron microscopy, X-ray diffraction and tensile testing. The experimental results show that a minor Sc addition to ZK60 alloy has an obvious effect on the refinement of the microstructure of the ZK60 alloy. During hot extrusion, incomplete dynamic recrystallization occurs in all the alloys, and the recrystallized grains become much finer with increasing Sc addition. The tensile strengths of ZK60 evidently increase with the addition of Sc, but the elongations decrease. The ZK60 alloy with 0.6% (mass fraction) Sc addition is found to have the tensile strength of about 350 MPa and the yield strength of about 280 MPa. After T6 heat treatment, the tensile strength of the alloy containing 0.6% Sc remains almost unchanged. However, the yield strength of the alloy increases up to 352 MPa, and the ratio of the tensile strength to the yield strength is close to 1.

Effects of scandium addition on electrical resistivity and formation of thermal hillocks in aluminum thin films

This study investigates the effects of doping aluminum (Al) films with minor amounts of scandium (Sc) on the electrical resistivity and the formation of thermal hillocks. The pure Al and Al–Sc films, prepared via sputtering deposition, before and after isochronal annealing are examined using a scanning electron microscope and a transmission electron microscope. In-situ thermal stress analyses of the films are also carried out. The grain size of the as-deposited films is reduced by addition of Sc. Moreover, the Sc can immobilize the grain boundaries, retarding grain growth and re-crystallization of the films during annealing. Although the as-deposited Al–Sc films show higher resistivity than that of a pure Al film, the former is significantly decreased after annealing at 300°C. The hillock density dramatically reduces with increasing the Sc concentration in the films. Average size of the hillocks in Al–Sc films clearly increases when the temperature is elevated.

Effect of scandium additions on pressure less sintering of Al-TiN metal matrix composites

Effect of scandium additions on pressure less sintering of Al-TiN metal matrix composites

Characterization and preparation of Mg–Al–Zn alloys with minor Sc

Mg–9Al–1Zn alloys with 0.3% Sc content (mass fraction) were prepared by ingot metallurgy. The effects of scandium addition on the microstructure and mechanical properties of the alloys have been investigated using optical microscope, scanning electron microscopy and tensile testing. It has been shown that the microstructure is mainly composed of α-Mg matrix, β-Mg 17Al 12 phase and Mg 5Al 4Sc intermetallic compound when 0.3% Sc was added. The scandium addition improves the morphology and distribution of Mg 17Al 12 phase, which substantially improves the mechanical properties of the alloy at both room temperature and high temperature.

Effect of Scandium Additions on the Tensile Properties of Cast Al-6Mg alloys

Effect of aging on the mechanical properties of Al-6Mg alloy doped with varying concentration of scandium ranging from 0.2 to 0.6 wt.% is analyzed. As-cast samples were aged isochronally for 60 min at different temperatures ranging from 100 to 500 °C. Evaluation of mechanical properties of the aged Al-6Mg (Sc) alloys was done by employing an Instron testing machine. Various strain rate of testing were used to find out the values of strain-rate sensitivity of the experimental alloys. The influence of scandium is much pronounced on yield strength than on the tensile strength. Alloys with higher scandium content have shown higher yield strength and the values of strain-rate sensitivity ‘m’ at peak-aged condition have been found to be comparatively high at higher scandium concentration. The fracture of the experimental alloys occurs through microvoid coalescence.

Modelling the Precipitation of Al3X Dispersoids in Aluminium Alloys and their Effect on Recrystallization

A combined model is presented that predicts the non-uniform distribution of Al3X dispersoid particles in commercial aluminium alloys containing zirconium and scandium and uses these predictions as inputs to a simple recrystallization model. The recrystallization model relies on knowledge of the stored energy in the sub-structure after deformation and this has been measured using electron backscattered diffraction (EBSD) techniques. The recrystallization model is based on the concept that partial recrystallization results from the non-uniform distribution of dispersoid particles due to their precipitation from a segregated cast structure. The model has been used to devise an improved homogenization treatment for AA7050, which uses an isothermal hold during heat up to maximize dispersoid nucleation. It has also been applied to predict the effect of scandium additions on recrystallization, investigate the factors that control the through thickness variation in recrystallized fraction, and interpret the results of experiments where the effect of strain rate have been studied.

Effect of scandium additions on microstructure and mechanical properties of Al–Zn–Mg alloy welds

The microstructure and mechanical properties of fusion zones of medium strength Al–Zn–Mg alloy (RDE-40) welds obtained by using different fillers containing various amount of scandium was investigated. It was observed that addition of scandium led to very significant grain refinement in the fusion zone especially for scandium levels greater than the eutectic composition (0.55 wt%). The grain refinement led to the reduction in solidification cracking and improved the tensile properties of fusion zone compared to the ones obtained by the commercial AA5556 filler.

Effect of Scandium Addition on Aging Behavior of 6061 Aluminum Alloy

It has been reported that scandium addition improved various properties of aluminum alloys. However, present authors can not find any reports about the addition of Sc to 6000 series alloys. In this study, Sc was added to 6061 alloy and various effects of the Sc addition on aging behavior were examined, comparing with Al-Sc binary alloy. In the STQ state, resistivity at 77K, ρD77, of 0.2%Sc added alloy (6061+Sc) was about 2.0n-m higher than the alloy of no addition (6061). The ρD77 increased in initial stage of isothermal aging up to 473K, then decreased. Though ρD77 of binary Al-0.176%Sc alloy began to decrease from 1.8Ms at 448K and 18ks at 523K, excess decrease in ρD77 of 6061+Sc corresponding to precipitation of Sc compounds was not clear. Peak value of the HV0.1 was decreased and peak aging time delayed by the Sc addition in aging up to 498K. However, softening by overaging was retarded by the Sc addition. These effects of the Sc addition are considered to come from vacancy trap by solute Sc atoms or interface between particles of Sc compound and matrix acting as vacancy sinks.