Y Alloy Research Articles

Microstructure evolution and simulation study of a duplex Mg–Li alloy during Double Change Channel Angular Pressing

The dual-phase Mg–9Li–3Al–2Sr–2Y alloy was extruded at 553K using Double Change Channel Angular Pressing (DCCAP) with an extrusion ratio of 17. The commercial code DEFORM-3D was used to develop a numerical model for deformation of the investigated material and the strain distribution, damage and grain shape evolution were predicted. The accurate computation of the material flow and deformation was performed, of which the results showed good agreement with microscope observations and micro-hardness measurements on the deformed billet and extrudate. Results suggest that dynamic recrystallization (DRX) occurs during the deformation and leads to grain refinement during the DCCAP process. The tensile strength and elongation after fracture in middle part of the extrudate show optimum values of 246.6MPa and 19.9%, respectively.

Constitutive modeling of Mg–9Li–3Al–2Sr–2Y at elevated temperatures

Hot deformation behavior of Mg–9Li–3Al–2Sr–2Y alloy was studied via hot compression tests in the temperature range of 423–573K with different strain rates ranging from 0.001 to 1.0s−1 using the Gleeble® 3500 thermal–mechanical simulation testing system at the University of Waterloo. A number of constitutive equation models including the Ludwik, Zener–Hollomon and modified Hensel–Spittel models were used to evaluate the correct material parameters for this alloy and assessed in terms of their ability to accurately predict the constitutive behavior. The analysis of the experimental data by the three constitutive models resulted in an excellent description of the flow curves. The results showed that the Ludwik and Zener–Hollomon models lead to a good agreement between the calculated and measured flow stresses during work softening. Whereas, the modified Hensel–Spittel equation was able to describe the entire deformation process for the deformation temperatures studied. The developed models were then applied to predict the stress strain behavior of this alloy under different thermomechanical behavior paths and showed good accuracy.

Microstructure and phase transformation of as-cast and annealed Mg–4Zn–1Y alloy containing quasi-crystal phase

By means of optical microscope (OM), X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analyses, the microstructures of as-cast and heat-treated Mg–4Zn–1Y (wt%) alloy containing quasi-crystal phase were studied. The microstructure of the as-cast alloy consists of α-Mg solid solution grains, intermetallic particles and eutectic phases (W-phase and I-phase), and huge grains with serious dendritic segregation are clearly observed. After heat treatment, phase transformation and dissolution occur in the alloy and many phases remain. When the alloy was treated above 410 °C, the eutectic phases transform into spherical shape as the I-phase turns to W-phase. After heat treatment for long time, the alloy is over burnt and the W-phase decomposes to Mg–Y binary phase.

Effect of pickling processes on the microstructure and properties of electroless Ni–P coating on Mg–7.5Li–2Zn–1Y alloy

The electroless plating Ni–P is prepared on the surface of Mg–7.5Li–2Zn–1Y alloys with different pickling processes. The microstructure and properties of Ni–P coating are investigated. The results show that the Ni–P coatings deposited using the different pickling processes have a different high phosphorus content amorphous Ni–P solid solution structure, and the Ni–P coatings exhibit higher hardness. There is higher phosphorus content of Ni–P amorphous coating using 125g/L CrO3 and 110ml/L HNO3 (w=68%) than using 180g/L CrO3 and 1g/L KF during pre-treatment, and the coating structure is more compact, and the Ni–P coatings exhibit more excellent adhesion with substrate (Fc up to 22N). The corrosion potential of Ni–P coating is improved and exhibits good corrosion resistance. As a result, Mg-7.5Li-2Zn-1Y alloy is remarkably protected by the Ni–P coating.

In vitro corrosion of Mg–1.21Li–1.12Ca–1Y alloy

The influence of the microstructure on mechanical properties and corrosion behavior of the Mg–1.21Li–1.12Ca–1Y alloy was investigated using OM, SEM, XRD, EPMA, EDS, tensile tests and corrosion measurements. The results demonstrated that the microstructure of the Mg–1.21Li–1.12Ca–1Y alloy was characterized by α-Mg substrate and intermetallic compounds Mg2Ca and Mg24Y5. Most of the fine Mg2Ca particles for the as-cast alloy were distributed along the grain boundaries, while for the as-extruded along the extrusion direction. The Mg24Y5 particles with a larger size than the Mg2Ca particles were positioned inside the grains. The mechanical properties of Mg–1.21Li–1.12Ca–1Y alloy were improved by the grain refinement and dispersion strengthening. Corrosion pits initiated at the α-Mg matrix neighboring the Mg2Ca particles and subsequently the alloy exhibited general corrosion and filiform corrosion as the corrosion product layer of Mg(OH)2 and MgCO3 became compact and thick.

Surface characteristics and fatigue performance of warm shot peened wrought magnesium alloy Mg–9Gd–2Y

The surface characteristics and fatigue performance of the warm shot peened Mg–9Gd–2Y alloys were investigated. Compared to conventional shot peening (SP) at room temperature, warm shot peening (WSP) at 240°C induces higher subsurface hardening and larger maximum compressive residual stress in the subsurface of the specimens. The optimum Almen intensity of WSP is 0·15 mm N, whereas it is 0·10 mm N for SP. The main reason is that the surface of warm shot peened specimen is more plastically deformed but less damaged at the optimum Almen intensity due to the increase in plastic deformation ability of the tested alloys at elevated temperature. The fatigue strength of the tested alloy at 107 cycles is increased from 125 to 175 MPa by optimum SP and to 185 MPa by optimum WSP.

Microstructure and mechanical properties of Mg–Li–Al based alloy with yttrium addition

The Mg–11Li–3Al–xY (LA113–xY, x = 0, 2·0; mass fraction, %) alloys were designed and prepared using a vacuum induction furnace by argon atmosphere, then processed by hot extrusion. The results show that, as yttrium (Y) is added, the LA113–2Y alloy mainly consists of β-Li, LiMgAl2 and Al2Y phases. The fine, granular and dispersed Al2Y phase is favoured for refining matrix crystals and optimising internal microstructure of the alloy. The microstructures of the investigated alloys are crushed into smaller phases, and obviously refined after hot extrusion process. As Y is added, the strength of the alloy also improves by the refining effect and the Al2Y phase. Specifically, the extruded LA113–2Y alloy exhibits a favourable combination of strength and ductility, with yield strength of 227·06 MPa, ultimate tensile strength of 239·65 MPa and elongation of 20·71%.

热处理对挤压变形Mg-7%Zn-0.6%Zr-0.5%Y合金低周疲劳行为的影响 *

对热挤压、时效处理（T5态）及固溶＋时效处理（T6态）Mg-7%Zn-0.6%Zr-0.5%Y合金（质量分数）分别进行了低周疲劳实验,探讨了热处理对合金低周疲劳变形行为的影响.结果表明：时效处理和固溶＋时效处理可提高热挤压Mg-7%Zn-0.6%Zr-0.5%Y合金的循环变形抗力;时效处理降低了合金的疲劳寿命,固溶＋时效处理可以提高合金在较高外加总应变幅下的疲劳寿命,但降低合金在较低外加总应变幅下的低周疲劳寿命;不同状态合金的弹性应变幅和塑性应变幅与载荷反向周次的关系可分别用Basquin和Coffin-Manson公式来描述;时效及固溶＋时效处理过程中形成的长周期堆垛有序结构（LPSO相）是合金的循环变形抗力大幅提高的主要原因,而疲劳变形过程中形成的孪晶可能是时效态合金疲劳寿命降低的原因.

Grain size stability and hardness in nanocrystalline Cu–Al–Zr and Cu–Al–Y alloys

Cryogenic high energy ball milling has been used to synthesize nanocrystalline Cu–14Al, Cu–12Al–2Zr and Cu–12Al–2Y alloys by mechanical alloying. The alloys were studied with the aim of comparing the effect of substituting Y and Zr in place of Al, in Cu–Al alloys, on the grain size stability at elevated temperatures. The as-milled alloys were subjected to annealing at various temperatures between 200 and 900°C and the resulting grain morphology has been studied using X-ray diffraction and transmission electron microscopy. The addition of Y results in significantly reduced susceptibility to grain growth whereas in case of CuAl and CuAlZr alloys, the susceptibility to grain growth was much higher. The hardness is substantially increased due to Zr and Y addition in the as-milled CuAl powders. However, the hardness of Cu–12Al–2Zr gradually decreases and approaches that of Cu–14Al alloy after the annealing treatment whereas in case of Cu–12Al–2Y alloy, the relative drop in the hardness is much lower after annealing. Accordingly, the efficacy of grain size stabilization by Y addition at high homologous temperatures has been explained on the basis of a recent thermodynamic stabilization models.

Effect of Yttrium addition on microstructure and mechanical properties of Mg–Zn–Ca alloy

The effects of Y on the microstructure and mechanical properties of the solution treated Mg–6Zn–0·5Ca alloys were investigated in this study. The results indicated that the alloy was mainly composed of α-Mg solid solution and the secondary phases of MgZn2, Ca2Mg6Zn3 and Mg12ZnY. The grains size of the solution treated alloys decreased from 210 to 80 μm with the increasing of Y content up to 1·5 wt-%. The great progressional mechanical properties were observed in the prepared Mg–6Zn–0·5Ca–1Y alloy at room temperature, the ultimate tensile strength (σb), tensile yield strength (σ0·2) and elongation (ϵ) were 284 MPa, 166 MPa and 14·7% respectively, which was determined by the combined contributions of solid solution strengthening, precipitation strengthening plus grain size refinement strengthening.

The electrochemical behaviors of Mg–8Li–0.5Y and Mg–8Li–1Y alloys in sodium chloride solution

The electrochemical performances of Mg–8Li–0.5Y and Mg–8Li–1Y electrodes in 0.7 mol L−1 NaCl solution are investigated by methods of potentiodynamic polarization, electrochemical impedance spectroscopy, potentiostatic oxidation and scanning electron microscopy (SEM). Their performances as anodes of Mg–H2O2 semi-fuel cells are also determined. It is found that the Mg–8Li–1Y electrode has higher corrosion resistant ability and electrooxidation activity than that of Mg–8Li–0.5Y electrode in 0.7 mol L−1 NaCl solution. The corrosion potential of Mg–8Li–1Y electrode is 60 mV more positive than that of Mg–8Li–0.5Y electrode. The current density of Mg–8Li–1Y electrode is around 2 mA cm−2 higher than that of Mg–8Li–0.5Y electrode at the discharge potentials of −0.8 V, −1.0 V and −1.2 V, and it is similar to that of Mg–8Li–0.5Y electrode at −1.4 V. The Mg–H2O2 semi-fuel cell with Mg–8Li–1Y anode presents a maximum power density of 59 mW cm−2 at room temperature, which is higher than that of Mg–8Li–0.5Y anode (53 mW cm−2). The content of Y in alloys obviously affects the performance of the alloys and the Y content of 1 wt. % is better than 0.5 wt. %.

Effects of yttrium and zinc on the texture, microstructure and tensile properties of hot-rolled magnesium plates

Pure magnesium, Mg–Y (1, 3, 5) and Mg–1Zn alloy (nominal composition, in wt%) were selected to examine the influence of alloying on the microstructure, texture and mechanical properties of Mg plates after hot-rolling and subsequent annealing. It was found that the maximum intensity of the rolled texture was markedly decreased with increasing Y additions but slightly increased by the Zn addition, in comparison with that of pure Mg. The texture weakening efficiency of Y addition declined with increasing Y concentration. The weakening of texture in Mg–Y alloys was attributed to the solute-driven effect, manifest as solute segregation at grain boundaries, which was evidenced by the TEM examination. Tensile testing revealed that the Mg–1Y alloy exhibited the highest elongation-to-failure of 30% at room temperature, and EBSD analysis suggested that the observed high room-temperature ductility was attributed to the weakened texture which favored the operation of the basal slip and tensile twinning.

Monocrystalline Al(As1–xNx)Si3 and Al(P1–xNx)ySi5–2y Alloys with Diamond-like Structures: New Chemical Approaches to Semiconductors Lattice Matched to Si

The reaction of M(SiH3)3 (M = P, As) with Al atoms from a Knudsen cell has recently led to an entirely new approach to the synthesis of (III–V)–(IV) alloys on Si substrates using gas-source molecular beam epitaxy. The main feature of these new materials is the presence of isolated “donor–acceptor” pairs within fully interlinked III–V–(IV)3 “building blocks”, leading to highly stable and crystalline structures with average diamond-like symmetry. Examples include stoichiometric compounds Al(P–As)Si3 as well as silicon-rich alloys (Si)5–2y(AlP)y. While these materials can be grown on Si with small mismatch strains, the complete elimination of the lattice mismatch may be important for applications such as photovoltaics which require thick films. Accordingly, in this paper we expand the above compositional space and explore the optical tuning potential in this new class of materials by introducing nitrogen onto the group V sublattice. We demonstrate that the addition of N(SiH3)3 into the reaction mixture under appropriate conditions readily yields novel Al(As1–xNx)Si3 and Al(P1–xNx)ySi5–2y alloys which exhibit enhanced optical absorption with respect to silicon as evidenced by spectroscopic measurements indicating potential applications in Si-based photovoltaics. These materials can be grown as monocrystalline layers completely lattice matched on Si via substitution of As and P by the markedly smaller N atoms. First-principles studies of the reactivity trends are consistent with the finding that a large excess of the less reactive N(SiH3)3 is needed to incorporate even minor amounts of the N atoms in the alloy products, up to ∼11% in the case of AlAs1–xNxSi3 but only ∼3% in the case of AlP1–xNxSi3. Molecular calculations are then combined with solid-state simulations to elucidate the path from “molecule to solid” by quantifying the structural changes associated with the incorporation of the Al–P–Si3, Al–As–Si3, and Al–N–Si3 tetrahedral cores into the solid. The main conclusions of this study are that severe departures from tetrahedral symmetry in the Al–N–Si3 building block thwart the assembly of a regular diamond lattice. This is in contrast to the AlAsSi3 counterpart, which is found to exhibit near perfect tetrahedral symmetry in the crystalline state. All compounds are predicted to be thermodynamically stable relative to their elemental reference states.

Experimental and calculated phases in two as-cast and annealed Mg–Zn–Y alloys

Abstract The CALPHAD (Calculation of Phase Diagram) method was used to select ternary alloys from Mg–Zn–Y system, aimed at determining the role of precipitates in the microstructure and texture evolution of Mg during and after deformation. The selected alloys are Mg–6Zn–1.2Y and Mg–5Zn–2Y. The constituent phases in the as-cast Mg–6Zn–1.2Y alloy are α-Mg solid solution phase and I (Mg3YZn6) intermetallic phase. The as-cast Mg–5Zn–2Y alloy is composed of α-Mg, I and W (Mg3Y2Zn3) phases. The intermetallics in the two alloys form by eutectic reaction, which in Mg–5Zn–2Y alloy results in initially W-phase formation and ultimately I-phase formation during solidification. After heat treatment, the Mg–6Zn–1.2Y and Mg–5Zn–2Y alloys contain nearly the same amount of ternary intermetallics (I and W phases, respectively) in equilibrium with α-Mg solid solution phase. The main solute in α-Mg phase is Zn with the same amount in the two alloys. The type and quantity of the phases obtained experimentally disagree with the results obtained from the thermodynamic database. One important discrepancy is that, in Mg–6Zn–1.2Y alloy, the I phase is not stable at the temperature of 430 °C, and that the W phase is the stable phase at this temperature. The differences in the experimental and calculated data indicate that the Mg–Zn–Y system requires to be reassessed with more experimental data.

Preparation and properties of Mg–Cu–Mn–Zn–Y damping magnesium alloy

Abstract This paper presents the successful preparation of a high-damping, high-strength Mg–Cu–Mn–Zn–Y alloy by alloying and extrusion. The damping capacity of the as-cast Mg–3Cu–1Mn alloy (alloy 1) displayed evident variations with changes in Y and Zn content. The as-cast Mg–3Cu–1Mn–2Zn–1Y alloy (alloy 2) exhibited excellent damping capacity and unusual damping growth in the high-strain amplitude stage; the damping capacity of alloy 2 exceeded that of alloy 1 and even approached that of pure Mg when the strain amplitude exceeded 5 × 10 −4 . This observation is believed to be related to the formation of long and parallel dislocation configurations and the interactions between these dislocations and plastic second-phase particles. The study also showed a remarkable improvement in the mechanical properties of as-extruded Mg–Cu–Mn–Zn–Y alloys. We attribute this finding to dynamic recrystallization, dispersion strengthening, and work hardening during hot extrusion.

The effects of calcium and yttrium additions on the microstructure, mechanical properties and biocompatibility of biodegradable magnesium alloys

In this study, the effects of calcium (Ca) and yttrium (Y) on the microstructure, mechanical properties, corrosion behaviour and biocompatibility of magnesium (Mg) alloys, i.e. Mg–xCa (x = 0.5, 1.0, 2.0, 5.0, 10.0, 15.0 and 20.0%, wt%, hereafter) and Mg–1Ca–1Y, were investigated. Optical microscopy, X-ray diffractometry (XRD), compressive and Vickers hardness testing were used for the characterisation and evaluation of the microstructure and mechanical properties. The in vitro cytotoxicity of the alloys was assessed using osteoblast-like SaOS2 cells. The corrosion behaviour of these alloys was evaluated by soaking the alloys in simulated body fluid (SBF) and modified minimum essential medium (MMEM) at 37 °C in a humidified atmosphere with 5% CO2. Results indicated that the increase of the Ca content enhances the compressive strength, elastic modulus and hardness of the Mg–Ca alloys, but deteriorates the ductility, corrosion resistance and biocompatibility of the Mg–Ca alloys. The Y addition leads to an increase in the ductility; but a decrease in the compressive strength, hardness, corrosion resistance and biocompatibility of the Mg–1Ca–1Y alloy when compared to the Mg–1Ca alloy. Solutions of SBF and MMEM with the immersion of Mg–xCa and Mg–1Ca–1Y alloys show strong alkalisation. Our research results indicate that Mg–xCa alloys with Ca additions less than 1.0 wt% exhibited good biocompatibility, low corrosion rate as well as appropriate elastic modulus and strength; whilst the Y is not a proper element for Mg alloys for biomedical application due to its negative effects to the corrosion resistance and biocompatibility.

Microstructure and texture evolution of Mg alloys during twin-roll casting and subsequent hot rolling

Microstructure and texture evolution of Mg–6Zn–1Mn–1Al (ZMA611) and Mg–6Zn–1Y (ZW61) alloys have been investigated. It is shown that recrystallization occurs through a shear (deformation) band nucleation mechanism. Alloy composition has a significant effect on the nature of the deformation bands formed during rolling, resulting in a difference in the orientation of recrystallized grains between the two alloys: double twin-related in ZMA611 and tension twin-related in ZW61. Such a contrast in microstructure results in the two alloys having different (00.2) pole figures.

Microstructures and mechanical properties of AZ91D alloys with Y addition

As-cast AZ91D + xY ( x = 0, 0.5, 1, 2 mass%) magnesium alloys were prepared by a simple addition of Y-rich interalloy to AZ91D alloy. Influences of Y on the microstructures and tensile properties of AZ91D alloy were investigated. Influences of extrusion temperature on the microstructure and tensile properties of AZ91D + 2Y alloy were investigated. Moreover, microstructures and the resulting tensile of extruded AZ91D + 2Y alloy were also investigated under different heat-treatment conditions. The results show that the addition of Y to AZ91D alloy refines primary α-Mg matrix and β-Mg 17Al 12 phase. The addition of 2 mass%Y forms rod-shaped Al 2Y phase. After hot extrusion, the grain sizes of AZ91D and AZ91D + 2Y alloys are greatly refined through dynamic recrystallisation. At extrusion temperature below 300 °C, the microstructure of AZ91D + 2Y alloy is characterized by fine and equiaxed grains, which leads to a high tensile strength but relatively low elongation. With increasing extrusion temperature up to 400 °C, more equiaxed grains with larger size are obtained. A low strength and large elongation are achieved compared with those extruded at low temperature. The best combination of both high strength and large elongation takes place at 325 °C. As for extruded AZ91D + 2Y alloy, solution treatment at 413 °C (T4) causes parts of broken β-Mg 17Al 12 phase to be dissolved into α-Mg matrix and the deterioration of tensile properties. During aging at 216 °C (T5), discontinuous precipitates appear at grain boundaries. Solid solution followed by aging (T6) treatment increases ultimate tensile strength but decreases yield strength and elongation.

Influence of rare earths addition on the corrosion behaviour of Zn–5%Al (Galfan) alloy in neutral aerated sodium sulphate solution

Abstract The effect of rare earth metal (Ce, Er, Y) additions on the corrosion behaviour of Zn–5Al Galfan alloy has been investigated. The corrosion resistance of Zn–5Al–1Ce, Zn–5Al–1Er and Zn–5Al–1Y alloys has been assessed by various electrochemical tests, such as corrosion potential measurements, polarization curves and electrochemical impedance spectroscopy. They have been performed in a 0.1 M Na 2 SO 4 solution, at approximately neutral pH, without stirring and in contact with the air. For comparison, the electrochemical tests have also been carried out on the Zn–5Al alloy. Moreover, the surface morphology and nature of the corrosion products have been investigated. The results indicated that rare earths’ addition improves the corrosion behaviour of Galfan, the effect being more pronounced for the Er- and Y-containing alloys. The mechanism by which the corrosion resistance of Zn–5Al alloy is enhanced in presence of the rare earths is discussed.

Mg–Gd–Y system phase diagram calculation and experimental clarification

Phase equilibrium of the Mg–Gd–Y system in Mg-rich corner was calculated in detail by phase diagram calculation software Pandat and thermodynamic database for Mg alloys. The calculated phase diagrams were compared with the key experimental results of DSC analysis for the alloys Mg–1 wt%Gd–7 wt%Y and Mg–5 wt%Gd–2 wt%Y. The solidification and precipitation process of the newly developed alloy Mg–12 wt%Gd–4 wt%Y–0.6 wt%Zr were analyzed. The detailed comparison strongly supports the reliability of the selected thermodynamic description based on the results of thermodynamic calculation. It is clarified that when the Mg–1Gd–7Y alloy ends its solidification and cools down continuously, the second phase Mg 24Y 5 firstly precipitated from solid solution of magnesium and then the GdMg 5 phase precipitated at relative lower temperature. But for Mg–5Gd–2Y alloy, the precipitation sequence of Mg 24Y 5 and GdMg 5 are in reverse order. Referring the calculated Mg–Gd–Y system phase diagrams, the suitable thermal mechanical processing and heat-treatment processes of newly designed and developed alloy Mg–12 wt%Gd–4 wt%Y–0.6 wt%Zr has been done.