Yu-long Wu

Bio: Yu-long Wu is an academic researcher from Central South University. The author has contributed to research in topics: Chemistry & Dehydrogenation. The author has an hindex of 2, co-authored 2 publications receiving 29 citations.

Intermetallic phase evolution of 5059 aluminum alloy during homogenization

Abstract: Intermetallic phase evolution of 5059 aluminum alloy during homogenization was investigated by means of optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive spectrometry (EDS), differential scanning calorimetry (DSC) and X-ray diffraction analysis (XRD). The results show that severe dendritic segregation exists in as-cast alloy. The dissolvable intermetallic phases in as-cast alloy consist of Zn- and Cu-rich non-equilibrium β (Al3Mg2) phase, Fe-rich eutectic Al6Mn phase and equilibrium Mg2Si phase. During the homogenization, Zn- and Cu-rich non-equilibrium β (Al3Mg2) phase, Fe-rich eutectic Al6Mn phase and equilibrium Mg2Si gradually dissolve into matrix. Fine dispersed β(Al3Mg2) particles and rod-shaped Al6Mn particles form in the Al matrix after homogenization. The proper homogenization processing is at 450 °C for 24 h, which is consistent with the results of homogenizing kinetic analysis.

Grain structure and microtexture evolution during superplastic deformation of 5A90 Al-Li alloy

Abstract: The microstructural evolution of banded 5A90 Al-Li alloy during superplastic deformation at 475 °C with an initial strain rate of 8×10−4 s−1 was studied using EBSD technique. The results showed that, before deformation, the grain shape appeared to be banded, the most grain boundaries belonged to low-angle boundaries, and the initial sheet had a dominate of {110}«112» brasstexture. During deformation, there were grain growth, grain shape change, misorientation increasing and textural weakening. The fraction of high-angle boundaries increased rapidly once the flow stress reached the peak value. Corresponding deformation mechanism for various stages of deformation was suggested. Dislocation activity was the dominant mechanism in the first stage, then dynamic recrystallization occurred, and grain rotation was expected as an accommodation for grain boundary sliding (GBS). At large strains, GBS was the main mechanism.

Catalytic depolymerization of lignin via transfer hydrogenation strategy over skeletal CuZnAl catalyst

Abstract: Selective cleavage of the aromatic CO bonds in lignin is a crucial step for lignin valorization to produce value-added chemicals, however, the development of efficient catalysts for mild conversions is still challenging. Herein, non-precious skeletal CuZnAl catalysts were firstly reported for the depolymerisation of lignin dimers and real organosolv lignin via the catalytic transfer hydrogenation (CTH) method. Typical lignin dimers, including α-O-4, β-O-4 and 4-O-5 types, were all effectively converted to the corresponding aromatics and alcohols in isopropanol under mild reaction condition. Furthermore, birch organosolv lignin was also well depolymerized into monophenols in 56.1 wt% yield. Experiments revealed that the water brought by the wet catalyst effectively promoted the CO bond cleavage, but slightly decreased the catalyst reactivity toward hydrogenation in isopropanol. Reaction evolution profiles and control experiments suggested that three reaction pathways were included, with the CO ether bond cleavage and subsequent hydrogenolysis taking precedence over the dehydrogenation or hydrodeoxygenation routes. This work provides an economical and environmentally-friendly method for the selective cleavage of lignin and lignin model compounds into value-added chemicals, which holds great promise in industrial application.

Control of second-phase particles in the Al-Mg-Mn alloy AA 5083

Abstract: The purpose of the present work is to understand the evolution of microstructure and microchemistry during homogenization of the Al-Mg-Mn alloy AA 5083 (Al Mg4.5 Mn0.7) and its influence on down-stream materials properties. The evolution of the particle state during solidification and subsequent homogenization annealing was tracked with a variety of experimental characterization methods and simulated with microchemistry models to analyse the changes in solute level and precipitation. Different homogenization practices were characterized by different sizes, volumes and densities of dispersoids which, in turn, had a clear impact on materials properties, including recrystallization behaviour and flow stress.

Ultrasonic spot welding of carbon fiber reinforced epoxy composites to aluminum: mechanical and electrochemical characterization

Abstract: The mechanical and electrochemical behavior of ultrasonic spot welded hybrid joints, made of AA5754 aluminum and carbon fiber reinforced epoxy with a co-cured thermoplastic surface layer, was studied. The effect of the welding parameters (energy and force) and the thickness of a thermoplastic film, applied as an upper ply in the composite lay-up, on the development of adhesion strength, was investigated. The best mechanical results were obtained when the welding parameters were able to achieve a large bonding area of mechanical interlocking between naked carbon fibers and aluminum and a better load distribution. The electrochemical results excluded the possibility of galvanic corrosion between aluminum and composite adherends thanks to the insulating action provided by the thermoplastic film.

Effect of friction coefficient in deep drawing of AA6111 sheet at elevated temperatures

Abstract: The effect of friction coefficient on the deep drawing of aluminum alloy AA6111 at elevated temperatures was analyzed based on the three conditions using the finite element analysis and the experimental approach. Results indicate that the friction coefficient and lubrication position significantly influence the minimum thickness, the thickness deviation and the failure mode of the formed parts. During the hot forming process, the failure modes are draw mode, stretch mode and equi-biaxial stretch mode induced by different lubrication conditions. In terms of formability, the optimal value of friction coefficient determined in this work is 0.15. At the same time, the good agreement is performed between the experimental and simulated results. Fracture often occurs at the center of cup bottom or near the cup corner in a ductile mode or ductile–brittle mixed mode, respectively.

A Review on Superplastic Formation Behavior of Al Alloys

Abstract: Superplastic formation technology is considered to be an effective and promising method to conquer formation difficulties of Al alloys, especially thin-walled or complex structure. In this paper, fundamentals of superplastic deformation of Al alloys are summarized and the superplastic deformation behaviors of main kinds of Al alloys are summarized and compared, including Al-Mg alloys, Al-Li alloys, and Al-Zn-Mg alloys as well as aluminum matrix composites. Then, the superplastic deformation mechanism for different Al alloys is thoroughly discussed. Last but not the least, the factors affecting the superplastic deformation process are fully analyzed.

The Effect of Concentration of Lawsonia inermis as a Corrosion Inhibitor for Aluminum Alloy in Seawater

Abstract: Lawsonia inermis also known as henna was studied as a corrosion inhibitor for aluminum alloy in seawater. The inhibitor has been characterized by optical study via Fourier transform infrared spectroscopy (FTIR). The FTIR proves the existence of hydroxyl and carbonyl functional groups in Lawsonia inermis. Aluminum alloy 5083 immersed in seawater in the absence and presence of Lawsonia inermis was tested using electrochemistry method, namely, electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PP). EIS and PP measurements suggest that the addition of Lawsonia inermis has caused the adsorption of inhibitor on the aluminum surface. The adsorption behavior of the inhibitor follow Langmuir adsorption model where the value of free energy of adsorption, , is less than 40 kJ/mol indicates that it is a physical adsorption. Finally, it was inferred that Lawsonia inermis has a real potential to act as a corrosion inhibitor for aluminum alloy in seawater.