Scandium Addition Research Articles

Spark plasma sintering of aluminum powders prealloyed with scandium additions

The objective of this research was to commence work on the spark plasma sintering (SPS) of Al–Sc alloys in an effort to develop fundamental data in this area. In this precursory study, a series of binary systems containing 0.1 to 0.4wt% Sc were processed in laboratory and industrial-scale equipment. Data revealed that all powders were responsive to SPS in both scenarios and that sintering temperature was a variable of critical importance. Hardness of as-sintered products scaled directly with Sc concentration but varied inversely with SPS temperature owing to in-situ aging of the raw powders. Hardness losses could be recovered through a post-SPS heat treatment into the T6 condition. Industrially processed slugs of Al-0.4Sc-T6 exhibited full densification and offered the highest hardness (786+/−8MPa). This was accompanied by a nominal tensile yield strength of 197MPa, UTS of 226MPa and tensile ductility of 11%.

Al–Mg–Si合金の再結晶挙動に及ぼすスカンジウムとジルコニウム添加の影響

Al–Mg–Si合金の再結晶挙動に及ぼすスカンジウムとジルコニウム添加の影響

Эвтектические сплавы на основе системы Al – Ca с добавкой скандия как возможная альтернатива термически упрочняемым силуминам

Эвтектические сплавы на основе системы Al – Ca с добавкой скандия как возможная альтернатива термически упрочняемым силуминам

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.

Synthesis of aluminum-based scandium–yttrium master alloys

The preparation technology for an Al–2% Sc–0.5% Y master alloy using aluminum–manganese alloys has been developed and tested. The microstructure of the prepared master alloy is studied and the compositions of intermetallics is determined. The efficient technological parameters of the synthesis are determined. It is shown that varying the compositions of starting reagents and alloying additions and optimizing the process conditions (temperature, mixing, etc.) allow us to forecast the manufacturing and operating characteristics of aluminum-based master alloys. Joint additions of scandium and yttrium oxides to a charge favor a substantial decrease in the grain size of the formed intermetallics; this effect appears to the utmost in the case of microallying with yttrium up to 0.5 wt %.

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.

Comparative study of the effect of lanthanum and scandium additives on anodic characteristics of AK1 alloy based on special-purity aluminum

Potentiostatic method was used to study the corrosion-electrochemical properties in a 3% NaCl electrolyte of an AK1 alloy modified with lanthanum and scandium. It was found that the lanthanum and scandium additives positively affect the corrosion resistance of the AK1 alloy in the NaCl electrolyte. For example, the additives reduce the anodic corrosion rate of the alloy by 3.6 × 10–4 to 0.97 × 10–4 g m–2 h–1. Upon alloying of the alloy, the pitting and corrosion potentials are shifted into the positive region, which indicates that alloys containing lanthanum and scandium become more pitting corrosion resistant.

Joint effect of scandium and zirconium on the recrystallization of aluminum Al–Mg2Si alloys

Metallographic analysis and hardness measurements are used to study the recrystallization processes in aluminum Al–Mg2Si alloys with scandium and combined scandium and zirconium additions that occur during annealing of the cold-deformed alloys at 100–600°C. The temperature of the onset of recrystallization of the Al–Mg2Si alloys with scandium and combined zirconium and scandium additions is shown to be 50°C higher than that of the alloys free from scandium and zirconium. It was noted that the small grain sizes of the alloyed compositions lead to weaker disordering during recovery and recrystallization.

Influence of scandium addition on the high-temperature grain size stabilization of oxide-dispersion-strengthened (ODS) ferritic alloy

The influence of 1–4at% Sc addition on the thermal stability of mechanically alloyed ODS ferritic alloy was studied in this work. Sc addition was found to significantly stabilize grain size and microhardness at high temperatures. Grain sizes of samples with 1 and 4at% Sc was found maintained in the nanoscale range at temperatures up to 1000°C with hardness maintained at 5.6 and 6.7GPa, respectively. The detailed microstructure was also investigated from EDS elemental mapping, where nanofeatures [ScTiO] were observed, while nanosized [YTiO] particles were rarely seen. This is probably due to the concentration difference between Sc and Y, leading to the formation of [ScTiO] favoring that of [YTiO]. Precipitation was considered as the major source for the observed high temperature stabilization. In addition, 14YT–Sc alloys without large second phases such as Ti-oxide can exhibit better performance compared to conventional ODS materials.

Achieving high superplasticity of a traditional thermal–mechanical processed non-superplastic Al–Zn–Mg alloy sheet by low Sc additions

The non-superplastic Al–Zn–Mg alloy sheet produced by a simple traditional thermal–mechanical processing can achieve high superplasticity at the temperatures ranging from 450 to 500°C and the strain rates ranging from 1×10−3 to 1×10−2s−1 by low scandium additions in the presence of 0.10% Sc (wt.%). An elongation of 1050% is obtained at 500°C and 5×10−3s−1. Analyses on the superplastic data reveal that the average values of the strain rate sensitivity and the activation energy of the Al–Zn–Mg–Sc–Zr alloy are about 0.5 and 85kJ/mol−1, respectively. The microstructural results show that the studied alloy consists of 3.14μm grains characterized by a high fraction of low angle grain boundaries and strong β-fiber rolling textures. During superplastic deformation, low angle grain boundaries gradually transfer into high angle grain boundaries to sustain grain boundary sliding, and the texture intensity diminishes. Besides, β-fiber rolling textures weaken and cube and random textures are dominant in the superplastic deformed alloy. Superior superplastic ductility of the Al–Zn–Mg–Sc–Zr alloy is ascribed to the coherent 10–20nm Al3ScxZr1−x particles that strongly retard recrystallization grain growth. Analyses of the superplastic data indicate that grain boundary sliding is the predominant deformation mechanism.

The effects of scandium on A356 aluminium alloy in gravity die casting

In this project, the addition of scandium into A356 aluminium alloy was studied for its effect on the mechanical properties as well as the changes in microstructure and eutectic morphology after casting process. Scandium addition was administered at the weight percentages of 0·2, 0·4 and 0·6. The results obtained in this work revealed that scandium can significantly enhance the mechanical properties of A356 alloy in terms of hardness and tensile strength. In general, the addition of 0·4 wt-% scandium in A356 alloy was found to be able to achieve the maximum tensile strength of 119·48 MPa as compared to 91·36 MPa for sample without scandium. Similarly, the sample with 0·4 wt-% scandium attained the maximum hardness of 20·36 HRA as compared to 17·32 HRA for unmodified A356. The mechanism that renders the enhancement in mechanical properties can be attributed to grain refinement. In SEM micrographs of samples with scandium, grain refinement can be observed in the microstructure and the morphology of eutectic structure. The eutectic morphology was also converted into a finer and fibrous structure.

The superplasticity of friction stir processed Al-5Mg alloy with additions of scandium and zirconium

Abstract The paper describes the effect of minor additions of scandium and zirconium on the superplastic behaviour of friction stir processed Al-5Mg based alloy. The measurements included the flow curves and tensile elongations of (in wt.%) Al-5Mg-0.1Zr, Al-5Mg-0.2Sc, and Al-5Mg-0.2Sc-0.15Zr alloys at initial strain rates ranging from 1 × 10−3 to 1 × 10−1 s−1, and at forming temperatures from 350 to 500°C. The inclusion of friction stir processing at tool rotation rates of 95 and 475 rpm considerably enhanced the superplastic behaviour of the Al-5Mg-0.2Sc-0.15Zr alloy, which was reflected in elongations without failure of over 1900%. Other friction stir processed alloys, treated at lower tool rotation rates, did not achieve superplasticity due to abnormal grain growth. The results yielded by the friction stir processed alloys are compared with the superplastic behaviour of the same alloys produced conventionally by cold rolling.

Scandium Influence on the Structure and Chemical Inhomogeneity of Welded Joints of Al-Zn-Mg-Cu System Alloys

Structural transformations and formation of chemical inhomogeneity in the weld and HAZ metal in fusion welding of complex alloy of V96 type were studied. It is shown that under the influence of welding heat, partial melting of the alloy phase components proceeds in the heat-affected zone with formation of structures of eutectic origin in the form of extended interlayers along the grain boundaries, causing metal embrittlement. Scandium addition to the alloy enables reducing the solidification processes and degree of segregation along the grain boundaries, as well as localizing partial melting of the grains without formation of coarse eutectic interlayers.

Effect of Sc/Zr ratio on the microstructure and mechanical properties of new type of Al–Zn–Mg–Sc–Zr alloys

Abstract The rare earth scandium (Sc) as a microalloying element has attracted an increasing interest in aluminum alloys for achieving excellent mechanical properties. Combining with zirconium, high strength and low price Al–Sc alloys are expected. The effects of Sc and Zr on the grain refinement, recrystallization resistance and precipitation hardening were investigated in new type of Al–Zn–Mg–Sc–Zr alloys by rolling, annealing and aging processes. Scandium addition into the Al–Zn–Mg alloys can efficiently refine the grain size and increase recrystallization resistance, especially together with zirconium addition. The maximum value of the yield-to-tensile strength (627 MPa/667 MPa) was obtained with 0.2Sc/0.4Zr ratio of the alloy after solution-aging treatment. The additional strengthening of the alloys is attributed to the grain refinement and the precipitation-strengthening effect of Al 3 Sc, Al 3 Zr or Al 3 (Sc, Zr) in the proper ratio of Sc/Zr during aging.

Effects of trace Be and Sc addition on the thermal stability of Al–7Si–0.6Mg alloys

In the present study, the effects of trace amounts of beryllium (Be, 0.05wt%) and scandium (Sc, 0.04wt%) addition on the microstructures and thermal stability of Al–7Si–0.6Mg alloys were investigated. The results show that traces of Be and Sc significantly reduce the amount of the iron-bearing phase and the interdendritic shrinkage. Be transformed the acicular iron-bearing phases into the nodular Al–Fe–Si iron-bearing phase, which is less harmful to ductility. Moreover, the addition of Be increased the Mg content of the solid solution within the matrix, prompting greater precipitation of the metastable Mg2Si phase after T6 heat treatment and effectively enhancing the mechanical properties of the alloy. However, during the following thermal exposure at 250°C for 100h, the metastable Mg2Si phase grew into the coarse β-Mg2Si equilibrium phase, resulting in a decrease in the mechanical strength of the alloy. Meanwhile, the addition of Sc had insignificant effect on the amount of metastable Mg2Si phase that precipitated. However, here, the iron-bearing phase was a nodular Al12Si6Fe2(Mg,Sc)5 phase, which significantly enhanced the density of the castings. After the same thermal exposure procedure, it was remarkably found that the precipitation of fine Al3Sc particles effectively inhibited grain growth and hindered the movement of dislocations. These factors led to the Sc-containing alloy having better mechanical properties (strength and ductility) than the alloys without Sc or with Be during the following thermal exposure at 250°C.

Effects of iron on intermetallic compound formation in scandium modified Al–Si–Mg Alloys

In general, iron has a strong tendency to dissolve in molten aluminum. Iron has very low solid solubility in aluminum–silicon casting alloys, so it will form intermetallic compounds that cause detrimental effects on mechanical properties. In this work, the effects of iron on intermetallic compound formations in scandium modified Al–Si–Mg alloys were studied. There were two levels of iron addition (0.2 and 0.4wt.%) and two levels of scandium addition (0.2 and 0.4wt.%). We found that the effects of scandium modification decreased with increasing iron addition. The morphologies of the complex intermetallic compounds were characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and electron backscatter diffraction (EBSD) techniques. It was found that scandium changes the morphology of Fe-rich intermetallic compounds from β-phase (plate-like) to α-phase, which reduces the harmful effects of β-phase.

Effect of Scandium Addition on Mechanical Properties and Corrosion Resistance of Medium Strength Al-Zn-Mg-Cu) Alloy

Al-Zn-Mg alloys are widely used construct material for wide range of application including automotive industry, building, and aviation. Scandium is rare earth metal, which modifies structure of semi-products and can lead to increasing of tensile and yield strength because of Al3Sc intermetallics of nanoscale size. This paper describes results of influence of small addition of scandium (0,08 wt. %) on mechanical and corrosion properties of cold-rolled sheets of 1913 alloy. 1913 is Russian medium strength corrosion resistant weldable Al-Zn-Mg alloy with addition of Cu for improvement of stress corrosion resistance and Mn with Zr for structure improvement. It is shown that addition of Sc transforms kinetics of artificial aging and accelerates decomposition of solid solution, besides tensile strength increases up to 50 MPa in artificially aged tempers. Changes in microstructure and quench sensitivity are described; results of intergranural corrosion, exfoliation and stress corrosion tests are introduced after different heat treatment including peak strength aging and overaging tempers.

Eutectic Morphology of Al-7Si-0.3Mg Alloys with Scandium Additions

The mechanisms of Al-Si eutectic refinement due to scandium (Sc) additions have been studied in an Al-7Si-0.3Mg foundry alloy. The evolution of eutectic microstructure is studied by thermal analysis and interrupted solidification, and the distribution of Sc is studied by synchrotron micro-XRF mapping. Sc is shown to cause significant refinement of the eutectic silicon. The results show that Sc additions strongly suppress the nucleation of eutectic silicon due to the formation of ScP instead of AlP. Sc additions change the macroscopic eutectic growth mode to the propagation of a defined eutectic front from the mold walls opposite to the heat flux direction similar to past work with Na, Ca, and Y additions. It is found that Sc segregates to the eutectic aluminum and AlSi2Sc2 phases and not to eutectic silicon, suggesting that impurity-induced twinning does not operate. The results suggest that Sc refinement is mostly caused by the significantly reduced silicon nucleation frequency and the resulting increase in mean interface growth rate.

Effect of prior cold work on tensile properties of Al–6Mg alloy with minor scandium additions

Effect of aging on the mechanical properties of cold worked Al–6Mg alloy with minor additions of scandium is studied. Cast and mechanically worked samples are isochronally aged for 60 min at different temperatures up to 500°C. Evaluation of mechanical properties of the aged alloys is done at various strain rates of testing. The m-values (strain rate sensitivity) of the experimental alloys are desired from the tensile test results. 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. The ‘m’ values are found to be comparatively high at peak aged condition of alloy with higher scandium content. The fracture of the experimental alloys occurs through microvoid coalescence.On étudie l’effet du vieillissement sur les propriétés mécaniques de l’alliage écroui d’Al-6Mg avec additions mineures de scandium. On a vieilli à durée égale pendant 60 minutes à différentes températures, jusqu’à 500°C, des échantillons moulés et formés mécaniquement. On fait l’évaluation des propriétés mécaniques des alliages vieillis par essai à différentes vitesses de déformation. On désire les valeurs de m (sensibilité à la vitesse de déformation) des alliages expérimentaux à partir des résultats de l’essai de traction. L’influence du scandium est beaucoup plus prononcée sur la limite d’élasticité que sur la résistance à la traction. Les alliages ayant une teneur plus élevée en scandium ont montré une limite d’élasticité plus élevée. On a trouvé que les valeurs de ″m″ étaient comparativement élevées sous la condition maximale de vieillissement de l’alliage ayant la teneur la plus élevée en scandium. La rupture des alliages expérimentaux se produisait par cupulation.

Theoretical Study of the Influence of Microalloying on Sensitization of AA5083 and Moderation of Sensitization of a Model Al-Mg-Mn Alloy via Sr Additions

The calculated effect of a range of quaternary alloying additions to aluminum alloy (AA)5083 (Al-4.4Mg-0.5Mn [UNS A95083]) was investigated. Attention was given to the influence of composition on the volume fraction of β-phase (Mg2Al3), and the possible formation of any additional phases (which we term γ-phase herein). Alloying additions of silver, cerium, copper, lithium, neodymium, nickel, scandium, silicon, strontium, yttrium, zinc, and zirconium were studied in hypothetical additions of 0.1 wt% and 0.5 wt%, revealing that there is potential to modify the fraction of β-phase, and hence sensitization, in AA5083. Calculations indicated strontium to be the most effective addition in decreasing β-phase fraction during thermal exposure (sensitization); therefore, the influence of Sr additions were studied empirically via production of custom Al-Mg-Mn alloys. Sensitization was investigated via the nitric acid mass loss test (NAMLT), revealing that mass loss from intergranular corrosion decreased by more than...