Trace Amounts Of Sc Research Articles

Study on quenching sensitivity of an Al–Zn–Mg–Cu alloy containing trace amounts of Sc and Zr

Study on quenching sensitivity of an Al–Zn–Mg–Cu alloy containing trace amounts of Sc and Zr

Effect of aging treatment on microstructure and mechanical properties of pure aluminum inoculated with Sc Zr element and graphene

Developing excellent performance conductors with high strength and electrical conductivity is a key issue in the electrical conductor industries. In this paper, an extruded composites containing trace amounts of Sc, Zr and graphene was prepared. Then all samples were extruded into round bars with a final diameter of 6.3 mm. Research results show that the UTS of one stage aging is 181 ± 2.7 MPa and the elongation is 21.4%. The hardness increases rapidly from 25.8HB(Brinell hardness) to 69.8HB within the first 12 h when the aging temperature at 280 °C. During the secondly stage aging, a peak electrical conductivity of 58.5%IACS(International annealed copper standard, 100%IACS = 58.0 MS m−1), which is obtained after a secondary aging at 380 °C for 48 h. A large number of nano-sized precipitates phase with smaller diameter are uniformly distributed throughout the matrix after aging at 280 °C for 24 h. With the increasing of aging time, the size of the precipitates phase increases significantly. This work also provides a good guideline for designing heat-resistant conductors.

Microstructure Evolution of High-Alloyed Al–Zn–Mg–Cu–Zr Alloy Containing Trace Amount of Sc During Homogenization

Microstructure evolution of a new high-alloyed Al–Zn–Mg–Cu–Zr–Sc aluminium alloy during two-stage homogenization process was investigated by use of scanning electron microscope, transition electron microscope and high resolution transition electron microscope. The results indicate that the morphology and chemical composition of Al3(Sc, Zr) particles formed in the first stage were greatly affected by heating temperature. With the increase of heating temperature, the morphology of Al3(Sc, Zr) particles transform from cuboidal with evident faceting to spheroidal due to improved Zr diffusivity. More Zr atoms enrich in the interface of precipitate/matrix forming a thin layer. Moreover, the mean diameter of precipitates increases a little bit with the increase of heating temperature, showing very restricted coarsening rate and high thermal stability of Al3(Sc, Zr) particles. After an appropriate second stage heat treatment (474 °C × 48 h), the intermetallic formed in the solidification process could dissolve sufficiently and Al3(Sc, Zr) particles still keep very good coherency with Al matrix without abnormal growth.

As-cast microstructure of Al–Zn–Mg–Cu–Zr alloy containing trace amount of Sc

It has been reported that the element scandium (Sc) is the most effective modificator which can significantly refine the grain size, prohibit recrystallization process and increase the strength. Adding trace of Sc in 7000 series aluminum alloys is considered to be an effective way to modify its microstructure and promote mechanical properties. In order to study the effect of Sc element on as-cast microstructure of Al–Zn–Mg–Cu–Zr alloy, ingots containing different amounts of Sc were prepared by ferrous-mold cast. Microstructures were characterized by means of differential scanning calorimeter (DSC), X-ray diffraction (XRD), optical microscope (OM) and scanning electrical microscope (SEM). The results indicate that when the Sc level exceeds a critical concentration, Al3(Sc,Zr) primary phase would form in the melt and act as an efficient nucleant, resulting in very refined grain and an equiaxed grain structure. Sc element reduces the number of eutectic phases formed during solidification, coupled with an increase in the concentration of major alloying elements retained in the solute. This behavior suggests possible benefits in improving the integrated properties of terminal products.

Microstructure, mechanical properties and stress corrosion cracking of Al–Zn–Mg–Zr alloy sheet with trace amount of Sc

Microstructural and property evolution of the Al–Zn–Mg–0.10%Sc–0.10%Zr alloy sheet during its preparation were investigated in detail by means of optical microscopy (OM), scanning electron microscope (SEM), energy dispersive X-ray (EDX), transmission electron microscopy (TEM), Vickers micro-hardness test and room temperature tensile test. Stress corrosion cracking (SCC) behavior of the Al–Zn–Mg–0.10%Sc–0.10%Zr alloy under different heat treatments was studied using slow strain rate test. The results showed that serious dendritic segregation existed in as-cast condition. The suitable homogenization treatment for Al–Zn–Mg–0.10%Sc–0.10%Zr alloy was 470°C/24 h. After homogenization treatment, dissoluble Zn and Mg enriched non-equilibrium phases dissolved into α-Al matrix completely. The suitable solid solution-aging treatment for Al–Zn–Mg–0.10%Sc–0.10%Zr alloy was solution treated at 470 °C for 60 min, followed by water quenching and then aged at 120 °C for 24 h. Under this aging temper, the grain structures were composed of sub-grains, ηʹ phases and nanometer-sized, spherical Al3(Sc, Zr) particles. Grain boundary precipitates (GBPs) area fraction was found to be an important parameter to evaluate the SCC susceptibility. The improved corrosion resistance from increasing aging temperature or prolonging aging time was due to the discontinuous η precipitates along the grain boundary and the high area fraction of GBPs. The main strengthening mechanisms of Al–Zn–Mg–0.10%Sc–0.10%Zr alloy are precipitation strengthening derived from ηʹ precipitates, dispersion strengthening, sub-grain strengthening and grain refinement caused by coherent Al3(Sc, Zr) particles.

Effect of minor Sc on microstructure and mechanical properties of Al–Zn–Mg–Zr alloy metal–inert gas welds

2.5mm thick cold-rolled Al–Zn–Mg–Zr alloy plates with trace amount of Sc were subjected to metal–inert gas (MIG) welding with Al–Mg–Sc as the filler metal. The influence of Sc additions on microstructure and mechanical properties of the welded joints was investigated by means of optical microscopy (OM), scanning electron microscope (SEM), energy dispersive X-ray (EDX), transmission electron microscopy (TEM), Vickers micro-hardness test and room temperature tensile test. Experimental results indicated that trace amount of Sc had significant effect on microstructure and mechanical properties of the joints. In both cases, base metal consisted of a typical fiber structure, different width of the equiaxed zones (EQZs) with fine grains were observed in the weld metal at the fusion boundary, fusion zones exhibited dendritic microstructure and average size of Al–Zn–Mg–0.10%Sc–Zr was 120μm, while in Al–Zn–Mg–0.25%Sc–Zr, grain size decreased drastically to 50μm. The grain refinement is mainly caused by the extremely fine, coherent Al3(Sc, Zr) particles with L12 structure, which act as heterogeneous nucleation. The observed grain refinement resulted in an appreciable increase in fusion zone strength and micro-hardness. Tensile strength of Al–Zn–Mg–0.25Sc–Zr alloy welded joint was 460MPa, approximately 11% higher than Al–Zn–Mg–0.10Sc–Zr alloy welded joint. Micro-hardness in the center of fusion zone rose from 95HV to 110HV. The main strengthening mechanisms of Al–Zn–Mg–Sc–Zr MIG welded joints are precipitation strengthening derived from η′ precipitates, dispersion strengthening and fine grain strengthening caused by coherent secondary Al3(Sc, Zr) particles.

Microstructures and properties of Al–Zn–Mg–Mn alloy with trace amounts of Sc and Zr

Abstract Microstructures and properties of Al–Zn–Mg–Mn alloy with trace amounts of Sc and Zr have been investigated. The results show that the addition of minor Sc and Zr to Al–Zn–Mg–Mn alloy can effectively refine grain size caused by the formation of Al 3 (Sc, Zr) particles with cubic L1 2 structure, which is coherent with α(Al) matrix. After solution treatment at 470 °C for 1 h, more homogenous recrystallization grains are observed in Al–Zn–Mg–Mn alloy; partial recrystallization occurs in Al–Zn–Mg–Mn–0.12Sc–0.12Zr alloy. However, Al–Zn–Mg–Mn–0.24Sc–0.12Zr alloy still remains an unrecrystallized fiber-like structure, which reveals that minor Sc and Zr can remarkably inhibit the occurrence of recrystallization. After aging treatment at 24 h for 120 °C, the tensile strength of Al–Zn–Mg–Mn–0.12Sc–0.12Zr alloy increased by 40 MPa as compared to Al–Zn–Mg–Mn alloy. When the Sc content increased to 0.24 wt%, the tensile strength of Al–Zn–Mg–Mn–0.24Sc–0.12Zr alloy reached a maximum. The main strength mechanisms are grain refinement strengthening with combined Sc and Zr additions and precipitation strengthening of Al 3 (Sc, Zr) particles. Compared with Al–Zn–Mg–Mn alloy, Al–Zn–Mg–Mn alloy with trace amounts of Sc and Zr exhibits higher corrosion resistance due to the discontinuity distribution of η precipitates along the grain boundary and the resistance effect on recrystallization behavior by Al 3 (Sc,Zr) particles.

Microstructural evolution of Al–Zn–Mg–Zr alloy with trace amount of Sc during homogenization treatment

The microstructural evolution of Al–Zn–Mg–Zr alloy with trace amount of Sc during homogenization treatment was studied by means of metallographic analysis, scanning electron microscopy (SEM), energy dispersive X-ray (EDX) and differential scanning calorimetry (DSC). The results show that serious dendritic segregation exists in studied alloy ingot. There are many eutectic phases with low melting-point at grain boundary and the distribution of main elements along interdendritic region varies periodically. Elements Zn, Mg and Cu distribute unevenly from grain boundary to the inside of alloy. With increasing the homogenization temperature or prolonging the holding time, the residual phases are dissolved into matrix α(Al) gradually during homogenization treatment, all elements become more homogenized. The overburnt temperature of studied alloy is 476.7 °C. When homogenization temperature increases to 480 °C, some spherical phases and redissolved triangular constituents at grain boundaries can be easily observed. Combined with microstructural evolution and differential scanning calorimeter, the optimum homogenization parameter is at 470 °C for 24 h.

Hot compressive deformation behavior and constitutive relationship of Al-Zn-Mg-Zr alloy with trace amounts of Sc

The hot deformation behaviors of Al-Zn-Mg-Sc-Zr alloy were investigated in a temperature range of 340–500 °C and a strain rate range of 0.001–10 s−1 using uniaxial compression test on Gleeble-1500 thermal simulation machine. The results show that the flow stress increases with increasing strain and tends to be constant after a peak value. The flow stress increases with increasing strain rate and decreases with increasing deformation temperature. The phenomenon of dynamic recovery and dynamic recrystallization can be observed by microstructural evolutions. Based on the hyperbolic Arrhenius-type equation, the true stresstrue strain data from the tests were employed to establish the constitutive equation considering the effect of the true strain on material constants (α, β, Q, n and A), which reveals the dependence of the flow stress on strain, strain rate and deformation temperature. The predicted stress-strain curves are in good agreement with experimental results, which confirms that the developed constitutive equations are suitable to research the hot deformation behaviors of Al-Zn-Mg-Sc-Zr alloy.

Hot Deformation Behavior of Al-Zn-Mg-Zr Alloy with Trace Amounts of Sc

The flow behavior of Al-Zn-Mg-Sc-Zr alloy during hot compression deformation was studied by thermal simulation test at strain rate of 0.001 to 10s-1 and deformation temperature of 340 to 500°C on the Gleeble-1500 thermal mechanical simulator. The results show that the flow stress increases with increasing strain rate, and decreases with increasing deformation temperature. The flow stress of the alloy during the elevated temperature deformation can be represented by a Zener-Hollomon parameter with the inclusion of the Arrhenius term. The values of A, n, α in the analytical expression of flow stress are fitted to be 1.49×1010s−1, 7.504 and 0.0114MPa−1, respectively. The hot deformation activation energy of the alloy during hot deformation is 150.25kJ/mol.

Simultaneous capillary electrophoretic determination of Sc(III) and Y(III) based on the complex-formation with a lacunary Keggin-type [PW 11O 39] 7− complex

Trace amounts of Sc(III) and Y(III) can react with [PW 11O 39] 7− to form the ternary Keggin-type complexes: [P(Sc IIIW 11)O 40] 6− and [P(Y IIIW 11)O 40] 6− having high molar absorptivities in the UV region. Since the rate of the complex-formation was very rapid and the kinetically stable ternary anions migrated in the capillary with different electrophoretic mobilities, the complex-formation reaction was applied to the simultaneous CE determination of Sc(III) and Y(III) with direct UV detection at 250 nm. For both Sc(III) and Y(III), the pre-column method provided linear calibration curves in the range of 2 × 10 −7 to 1 × 10 −5 M; the respective detection limits were 1 × 10 −7 M (the signal-to-noise ratio = 3). The proposed method was successfully applied to the determination of Sc(III) and Y(III) in river water.