Yuansheng Yang

Institute of Metal Research, Chinese Academy of Sciences

In this paper, the isothermal oxidation experiments were used to study the effect of Ag on the high-temperature oxidation behavior of Mg–6.5Gd–5.6Y–0.1Nd–0.01Ce–0.4Zr (wt%) alloy oxidized at 350 °C, 400 °C and 450 °C for 120 h. The results show that the oxidation weight gain of the alloy mainly occurs in the early oxidation stage (0–20 h). This rea...

The effects of B addition on microstructure and mechanical properties of a γ′-strengthened CoNi-base superalloy are investigated. The addition of B leads to a substantial increase in the volume fraction of both the eutectic structure and borides. The CoNi-base alloy shows a high solubility limit for the element B. Borides become noticeable in the a...

Exfoliation corrosion (EFC) has rarely been reported for wrought magnesium alloys. Enhanced EFC of the as-extruded Mg–1Li–1Ca alloy was observed after the removal of outermost fine-grained skins. The microstructure and corrosion products were investigated using optical microscopy, scanning electron microscopy, electron backscattered diffraction, X-...

In order to understand the effects of drawing velocity, initial grain size and texture on the microstructure evolution during directional annealing, a cellular automata model based on grain boundary (GB) curvature, GB energy and GB mobility was established with a modified calculation model of the GB curvature. The simulation results show that there...

In order to impart electrical conductivity to the magnesium alloy micro-arc oxidation (MAO) coating, the electroless copper plating was performed. Effects of plating temperature and complexing agent concentration on the properties of the electroless copper plating layers were studied by measuring their microstructure, corrosion resistance and elect...

The effect of extrusion parameters on the residual stress in the extruded magnesium rod is investigated through FEM. The residual stress on the surface and in the center of the extruded rod is tensile and compressive, respectively, with the axial residual stress showing the highest magnitude. The extrusion temperature is the most influential factor...

Reducing the local stress in the vicinity of the grain boundaries is a favorable way to improve the super-elastic properties of super-elastic alloys. The crystal plasticity finite element method (CPFEM) was applied in this study to simulate the deformation behavior and local stress of a super-elastic Cu-8Al-11Mn (wt.%) alloy containing single grain...

The microstructure and mechanical properties of Mg-6Zn-1Al-0.3Mn under different heat treatments were investigated. The results show that the two-stage solution treatment is obviously better than single-stage solution treatment, and all the MgZn phases nearly dissolve into the matrix after 335 °C × 4 h + 385 °C × 8 h solution treatment. Both the so...

The Ni impurity existing in electrolytic Mg cannot be removed using the common settling method since there is a deep eutectic reaction between Ni and Mg. Thermodynamic calculations in this work indicate that the equilibrium solute distribution coefficients of Ni between solid and liquid Mg above the eutectic temperature are far less than 1. The dir...

The microstructure and tensile properties of hot-extruded Al-8Zn-2Mg-2Cu-0.15Zr alloy (7055 alloy) with the minor addition of Sc were investigated. The 0.1 and 0.2 wt.% Sc were added into 7055 alloy during the preparation process by conventional casting. Attributing to the Sc additions, the grain sizes of as-cast ingots were remarkably refined and...

An investigation into the corrosion characteristics and mechanism of directionally solidified (DSed) Mg-3Zn-xCa (x = 0, 0.2, 0.5, 0.8 wt.%) alloys in 0.9 wt.% NaCl solution is presented. The DSed microstructure consists of columnar dendrites and eutectics distributed in the interdendritic region. The primary dendritic arm spacing (PDAS) and the vol...

This study combines machine learning and a phase diagram to accelerate the design of a cobalt-based superalloy with a composition of Co-30Ni-10Al-6Ta (at%). The results show that Co-30Ni-10Al-6Ta alloy exhibits high γ′ solvus temperature (1,215 °C) and high yield strength (1,220 Mpa at 25 °C), which is comparable with commercial nickel-based polycr...

Achieving high strength in Mg alloys is usually accompanied by ductility loss. Here, a novel Mg97Y1Zn1Ho1 at. % alloy with a yield strength of 403 MPa and an elongation of 10% is developed. The strength-ductility synergy is obtained by a comprehensive strategy, including a lamella bimodal microstructure design and the introduction of nano-spaced so...

Magnesium alloys with homogeneous degradation and controlled degradation rate are desirable for biodegradable materials. In the present work, Mg-3 wt.%Zn-0.2 wt.%Ca alloys with different columnar structures were fabricated and the degradation in 0.9 wt.% NaCl were investigated. With the increase of the growth rate for the directional solidification...

In the present work, the effect of heat treatment on the cyclic deformation behavior of as-extruded ZA81M magnesium alloy was investigated. Two heat treatment conditions were applied to the as-extruded ZA81M alloy: a solution treatment (T4, 653 K for 40 h and quenched with 298 K water) and a solution treatment plus artificial aging (T6, 348 K for 3...

A Mg-3 wt.%Zn-0.2 wt.%Ca alloy was fabricated by directional solidification, and its mechanical and corrosion properties were investigated from different crystallographic orientations. It was found that the directionally solidified (DSed) Mg-3Zn-0.2Ca alloy had a cellular structure with a preferred <11-20> growth orientation. The {0001} basal plane...

The coarsening behavior of the γʹ precipitates and compression deformation mechanism of the γʹ-strengthened CoNi-base superalloys are investigated. By substituting 1 at.% Ta for 1 at.% W, the 4W2Ta alloy exhibits a higher γʹ solvus temperature of 1218 °C and a lower mass density of 8.93 g/cm³. During the aging process from 900 to 1000 °C, both of t...

In this paper, the influence of the Sn element on the melt viscosity, grain size, shrinkage, and tensile properties of the sub-rapidly solidified Mg-6Al-4Zn alloy was studied. The results showed that the melt viscosity of the Mg-6Al-4Zn alloy was greatly decreased because of the addition of Sn. As the content of Sn increased from 0 to 1.8 wt.%, the...

In this study, Mg–6.0Zn–3.0Sn–0.5Mn (ZTM630) magnesium alloy was pre-activated by colloidal Ti, oxalic acid, and phosphoric acid, and a phosphate conversion coating (PCC) was prepared on the alloy surface. The morphology and corrosion resistance of the prepared PCCs were investigated. Surface morphology studies showed that the phosphate crystals th...

Interfacial segregation is ubiquitous in mulit-component polycrystalline materials and plays a decisive role in material properties. So far, the discovered solute segregation patterns at special high-symmetry interfaces are usually located at the boundary lines or are distributed symmetrically at the boundaries. Here, in a model Mg−Nd−Mn alloy, we...

The corrosion behaviors of ferrite-pearlite steels before and after intermediate quenching treatment were compared in the simulated bottom plate environment of cargo oil tanks. The results indicate that all tested steels exhibited an enhanced galvanic corrosion caused by the accumulated Fe3C. However, the corrosion resistance of steels could be imp...

The microstructure, phase transformation temperature, γ/γ′ lattice misfit, and mechanical properties of Co-4Ti-10V-2W-2Ta (at. %, referred to as 2Ta) quinary alloy were investigated in detail. In addition, the results show that Ti, W, and Ta exhibit a strong partitioning tendency to the γ′ phase, resulting in a high γ′ solvus temperature (~1131 °C)...

In this study, CoCr2Ni2AlTi, Co2Cr2Ni2AlTi and CoCr2Ni3AlTi alloys are prepared using vacuum arc melting furnace. The morphology, microstructure, compositions and corrosion behavior in 3.5 wt% NaCl solution or 0.5 M H2SO4 solution are investigated by means of scanning electron microscope (SEM), X-ray diffraction (XRD), energy dispersive spectromete...

The shrinkage microporosity formed during the directional solidification of Ni-based single crystal superalloys can significantly reduce the fatigue life of turbine blades, which may lead to a catastrophic flight accident due to the failure of aeroengines. We developed an integrated mesoscale model, which combined the shrinkage pressure drop from d...

The effect of the quenching rate after solution treatment on the residual stress and precipitation behavior of a high strength Mg-5Zn-3.5Sn-1Mn-0.5Ca-0.5Cu plate is studied. The simulation results show decreasing temperature gradient in the plate with decreasing quenching rate, which leads to weakened inhomogeneous plastic deformation and decreased...

Understanding how intrinsic defects impact magnesium (Mg) crystals mechanics is of prime importance for engineering applications. In this work, the mechanical performance of Mg crystals with cracks at the nanoscale was studied using molecular dynamics method. Influence of the nano-crack type and size on the deformation behavior of Mg crystals was a...

Poor corrosion resistance of magnesium alloys remains a major obstacle to their extensive application. Phosphate conversion coating (PCC) is one of the most direct and effective strategies to enhance the corrosion resistance of magnesium alloys. To overcome the environmental damage of traditional phosphating technology, a PCC free of fluorine, chro...

A comparative study on the microstructures and mechanical properties of the extruded Mg-xCa/Mn/Ce (x = 0.25, 0.5, 1, 2.0 wt%) alloys and pure Mg has been carried out. It was found that when the addition of Ca, Mn and Ce was more than 0.25 wt%, 0.5 wt% and 0.5 wt% respectively, microstructures with fine grain sizes smaller than 5 μm can be achieved...

The evolution of the microstructure and microsegregation in a new type of Mg–6Al–4Zn–1.2Sn (wt%) cast magnesium alloy solidified at cooling rates from 4.5 × 10¹ °C s⁻¹ to 2.3 × 10³ °C s⁻¹ is investigated. The results indicate that the secondary dendrite arm spacing and the average grain sizes decrease from 14.3 to 2.9 μm and from 187 to 78 μm, resp...

A novel method of pulsed magnetic field (PMF) treatment was developed to eliminate the residual stress of rolled magnesium alloy AZ31 sheet in this study. The effect of PMF on residual stress of rolled AZ31 sheet was investigated and its mechanism was analyzed. The experimental results revealed that the pulse frequency had a significant impact on r...

This work investigated the microstructure, mechanical properties and corrosion behavior of dual-phase (DP) steel after different intercritical quenching treatment and compared the results with commercial AH32 steel. The results indicate that the microstructure of all tested DP steels was composed of lath martensite and polygonal ferrite. As the tem...

Magnesium alloys exhibit significant potential for use in next-generation biodegradable materials. Implanted magnesium alloys are expected to exhibit good wear resistance. In this work, the effects of rare earth metal Sc on the wear resistance of biodegradable magnesium alloys were studied. The average grain sizes of Mg–1.5Zn–0.6Zr–xSc (ZK21–xSc, x...

The effect of Ca on the microstructure and mechanical properties of directionally solidified (DSed) Mg-3Zn-xCa alloys (x=0.2,0.5,0.8wt.%) was investigated in the present work. The results showed that the DSed samples with the growth rate of 120 μm/s had columnar dendritic structures and the primary dendritic arm spacing (PDAS) decreased with the co...

The coarsening behavior of γʹ precipitates at different temperatures and the compression deformation mechanism of a novel Co–V–Ta–Ti superalloy are investigated. It is found that the coarsening behavior of the γʹ precipitates follows the classical Lifshitz-Slyozov-Wagner (LSW) model based on measured results of the temporal evolution of the mean ra...

The effect of the pulsed magnetic field on the grain refinement of superalloy K4169 has been studied in directional solidification. In the presence of the solid–liquid interface condition, the distributions of the electromagnetic force, flow field, temperature field, and Joule heat in front of the solid–liquid interface in directional solidificatio...

The tensile strengths of the as-extruded Mg–Al–Ca ternary alloys at both ambient and elevated temperatures are enhanced via adding a high content of Ca element up to 6 wt%. High-temperature strength of the present rare-earth-free Mg alloys can be even compared with those of the reported Mg-RE alloys. The as-extruded Mg–6Al–6Ca (wt. %, AX66) alloy e...

The low voltage pulsed magnetic field (LVPMF) disrupts the columnar dendrite growth, and the columnar-to-equiaxed transition (CET) occurs during the directional solidification of superalloy K4169. Within the pulse voltage ranging from 100 V to 200 V, a transition from columnar to equiaxed grain was observed, and the grain size decreased as the puls...

A model for crystal growth in multi-directional flowing melt was built to study the crystal morphology evolution during solidification under forced convection. Based on the model, the formation of non-dendritic structure of Ni-based alloy solidified with forced convection was numerically investigated by the cellular automata method. The results ind...

Minimizing pore size during directional solidification is critical for reducing the risk of failure for Ni-based superalloys. In this study, the pore size distribution as a function of casting conditions during the entire single crystal casting was obtained by two-dimensional optical metallography and three-dimensional X-ray microtomography. Then,...

Directionally solidified Mg-4wt-% Zn alloy was prepared and the effect of growth rate on its microstructure evolution and mechanical properties was investigated. A typical cellular structure was observed when the growth rate was lower than 60 µm s⁻¹. The microstructure evolved from cell to columnar dendrite as the growth rate increased. The ultimat...

This article aims to explore the age hardening responses of both as-extruded and as-aged Mg-2.5Sn-1.5Ca-xAl alloys (x = 2.0, 4.0 and 9.0 wt%, termed TXA322, TXA324 and TXA329, respectively) through microstructural and mechanical characterization. Results indicate that grain size of as-extruded TXA322, TXA324 and TXA329 alloys were ∼ 16 μm, ∼ 10 μm...

The hot deformation behavior of Mg-5Zn-3.5Sn-1Mn-0.5Ca-0.5Cu alloy containing coarse second phase particles is studied. The flow stress increases with decreasing temperature and increasing strain rate. The stress-strain result is fitted to the hyperbolic sine equation to obtain the constitutive equation of the alloy. The processing map is construct...

The mechanical anisotropy of directionally solidified Mg-4 wt.% Zn alloy was studied under compression test at room temperature. The results show that directionally solidified Mg-4 wt.% Zn has higher compression strength and work hardening rates when compression axis is parallel to the growth direction, which is mainly due to the formation of {101‾...

The degradation behavior of Mg-4 wt% Zn alloy with three different microstructures was examined in Hank's solution at 37 °C by electrochemical measurements and immersion tests in this study. The results show that the sample with cellular structure exhibits a more positive corrosion potential, lower corrosion current density, larger impedance and mo...

The microstructure and mechanical properties of Mg–6Zn–2Sn–0.5Mn–xAl (x = 0, 1, 2, 3) alloy are investigated. The addition of Al leads to the refinement of grain size and the formation of Al6Mn, Mg32(Al,Zn)49 also forms when the amount of Al is higher than 2 wt-%. Because of the addition of Al, the precipitates in the alloy after ageing treatment a...

The microstructural evolution and compression property of a novel γʹ-strengthened CoNi-base superalloy have been investigated. The directionally solidified CoNi-base superalloy possesses a lower density of 9.03 g/cm³ and a higher γʹ solvus temperature of 1166 °C, compared with those of the Co–Al–W-base superalloys with high level of W element. Afte...

The previous study has shown that the mechanical properties of extruded Mg–Zn–Al–Sn alloys decrease with the increasing of extrusion temperature because of the coarsened microstructure. In order to improve the microstructure of Mg–Zn–Al–Sn alloy extruded at a high temperature, a small amount of Mn (0.6 wt%) was added to Mg–4Zn–2Al–2Sn (ZAT422, wt%)...

The electromagnetic field is interested increasingly for its powerful means to control the solidification process. The solidification microstructure can be effectively controlled by the transfer processes with electromagnetic field during solidification. Based on the interaction of the pulsed magnetic field and metallic melt, for example, the as-ca...

It has been found that the crystal morphology during equiaxed solidification can be strongly changed by the applied physical fields, such as the electromagnetic field, ultrasonic treatment or mechanical stirring. Theoretically, the applied external fields cause melt flow to impact the crystal growth and thus change the solidification structure. How...

Grain refinement of pure copper solidified with the low voltage pulsed magnetic field (LVPMF) has been achieved in our previous experiments. To further study the influence of solidification condition on the as-cast structure and the relevant mechanism, the numerical investigation of grain growth of pure copper under LVPMF was conducted in the prese...

Microstructure of Mg-5Zn-3.5Sn-1Mn-0.5Ca-0.5Cu alloy is studied after hot compression tests. The processing map is constructed using the strain rate sensitivity parameter from the power-law form of the constitutive equation. To identify the microstructure evolution for deformation conditions outside and inside the region suitable for hot processing...

A new Mg-5Zn-3.5Sn-1Mn-0.5Ca-0.5Cu alloy with high strength is developed and the microstructure and mechanical properties of the alloy in the as-cast, extruded and aged states are investigated. The as-cast alloy contains α-Mg, MgZn2, Mg2Sn and MgSnCa phase. The extrusion process refines the microstructure and leads to fully dynamic recrystallized g...

In this paper, empirical dynamic recrystallization (DRX) models for the semicontinuous AZ31 magnesium alloy were established based on the stress–strain curves and microstructure observations generated from hot compression tests. The DRX evolution during the seamless tube extrusion of the alloy was studied by numerical and experimental methods. The...

Heretofore, recognitions of the systematic effects of scandium addition on corrosion behavior of biodegradable magnesium alloys are not yet clear. In the present study, a series of Mg–1.5Zn–0.6Zr–xSc (ZK21–xSc, x = 0, 0.2, 0.5, 1.0 wt.%) alloys were casted and investigated with respect to the immersion and electrochemical degradation behavior. The...

In the present study, an AZ31B magnesium alloy was welded using a low-power pulsed Nd:YAG laser attached to a six-axis welding robot. The welding metallurgical characteristics, including microstructure, porosity formation, texture evolution and microhardness distribution were systematically investigated using a scanning electron microscope (SEM), e...

Microstructures, elemental partition behavior, phase stabilities and mechanical properties of Nb- and W-containing Co-V-Ti-based superalloys were investigated. Elemental partition coefficients (KX = Cγ’/Cγ) of Nb and W in Co-V-Ti-based superalloys are 2.07 and 1.10, respectively. The γ’ solvus temperatures are determined as 1023 °C, 1055 °C and 103...

The hot working flow stress of as-cast and two as-extruded magnesium alloys ZK60 was investigated through uniaxial compression tests. It was found that the hot deformation behavior was sensitive to the deformation conditions and initial microstructure. The peak flow stress was affected by the deformation temperature and the strain rate. Its value w...

In this work, the microalloying approach was adopted to improve the mechanical properties of Mg-6Zn-0.5Zr alloy by co-addition of trace Cu and Ce elements. The results showed that the grain size of the Mg-6Zn-0.5Zr-0.5Cu-0.5Ce alloy was refined, and MgZnCu and Mg-Zn-Ce phases formed by the microalloying of Cu and Ce. In addition, high-density nano-...

Heretofore, understandings about the effects of scandium on properties of magnesium alloys for biodegradable implant applications are extremely limited. In the present study, four Mg–1.5Zn–0.6Zr–xSc (ZK21–xSc, x = 0, 0.2, 0.5, 1.0 wt%) alloys were fabricated and investigated with respect to the microstructure and mechanical properties. Microstructu...

The automatic TIG welding on AZ31B alloys was carried out by the six-axis robot in the present work. After post-welded heat treatment (PWHT), the microstructure, precipitates, and mechanical properties of the AZ31B joints were investigated by using the optical microscope (OM), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy...

The Al–Mg–Y system was critically assessed by means of the CALPHAD technique. The solution phases of liquid, face-centered cubic (FCC), body-centered cubic (BCC) and hexagonal close-packed (HCP) were modeled with Redlich–Kister equation. The thermodynamic models of compounds Al12Mg17, Al30Mg23 and Al3Mg2 in the Al–Mg system, AlY2, Al2Y3, AlY and Al...

The immersion and electrochemical degradation behaviors of as-extruded Mg-1.5Zn-0.6Zr-0.2Sc (ZK21-0.2Sc) alloy in Hank's solution with and without albumins were investigated and the influencing mechanism was elucidated. The immersion experiment showed that the presence of albumins could inhibit the corrosion of the ZK21-0.2Sc alloy through the adso...

In this study, an approach is proposed to improve the microstructure and mechanical properties of Mg-4Zn-0.5Zr alloy by combining trace Cu and rare earth Ce addition. The results showed that Cu and Ce additions led to obvious grain refinement and the formation of Mg-Zn-Cu and Mg-Zn-Ce phases. The Mg-Zn-Ce phase was identified to have an orthorhombi...

A new efficient micro-arc oxidation technology was developed for AZ80 magnesium alloy, the treating time was shorten to 3 min compared to the conventional micro-arc oxidation process. The surface morphologies and cross section morphology of the coatings were analyzed by scanning electron microscopy (SEM) and X-ray energy dispersive spectroscopy (ED...

Previous numerical inverse method to calculate composition-dependent interdiffusivity with one diffusion couple can encounter with low calculation efficiency due to the unavoidable diffusion simulation procedure. The present work applies the numerical inverse method to the integrated form of diffusion equation, degenerating the original inverse pro...

The quench induced residual stress in extruded ZK60 magnesium alloy is investigated. X-ray diffraction and layer removal technique are employed to determine the residual stress in extrusion and long transverse direction through the thickness of the extruded plate after solution and quenching treatment. FEM simulation is employed to clarify the orig...