Xingwu Guo
Shanghai Jiao Tong University
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Featured researches published by Xingwu Guo.
Materials | 2014
Xi-Shu Wang; Xingwu Guo; Xu-Dong Li; Dong-Yun Ge
In this paper, rotating bending fatigue tests of 2024-T4 Al alloy with different oxide coatings were carried out. Compared to the uncoated and previously reported oxide coatings of aluminum alloys, the fatigue strength is able to be enhanced by using a novel oxide coating with sealing pore technology. These results indicate that the better the coating surface quality is, the more excellent the fatigue performance under rotating bending fatigue loading is. The improvement on the fatigue performance is mainly because the fatigue crack initiation and the early stage of fatigue crack growth at the coating layer can be delayed after PEO coating with pore sealing. Therefore, it is a so-called synergistic coating technology for various uses, including welding thermal cracks and filling micro-pores. The effects of different oxide coatings on surface hardness, compressive residual stress, morphology and fatigue fracture morphology are discussed. A critical compressive residual stress of about 95–100 MPa is proposed.
Transactions of Nonferrous Metals Society of China | 2007
Jian-Wei Chang; Xingwu Guo; Peng-huai Fu; Liming Peng; Wenjiang Ding
Abstract The corrosion behaviour of Mg-3.0Nd-0.4Zr (NK30) magnesium alloy was investigated in as-cast (F), solution treated (T4) and peak-aged (T6) conditions in 5% NaCl solution by immersion tests and electrochemical measurements. The results of immersion test show that NK30 alloy exhibits better corrosion resistance in F condition than it does in the other two conditions due to the more compact corrosion film formed on alloy in F condition. The potentiodynamic polarization curves show that the overpotential of cathodic hydrogen evolution reaction on NK30-F is much higher than that on NK30-T4 and NK30-T6. The corrosion potentials of NK30 increase in the following order: F
Transactions of Nonferrous Metals Society of China | 2014
Shaohua Wang; Xingwu Guo; Can Sun; Jia Gong; Liming Peng; Wenjiang Ding
Abstract To improve the corrosion resistance, electrodeposition of Cu coating on Mg–3.0Nd–0.2Zn–0.4Zr (mass fraction, % NZ30K) magnesium alloy via an appropriate pretreatment was investigated. The surface morphologies, compositions and microstructures of the pretreated films and Cu coating were characterized in detail. The results show that the activation film consists of fluoride and phosphates and Zn immersion film forms preferentially on the eutectic compound Mg 12 Nd phase region. A smooth, uniform and dense Cu coating is successfully obtained. Potentiodynamic polarization tests reveal that Cu coating can greatly improve the corrosion resistance of NZ30K magnesium alloy. Open circuit potential (OCP) and electrochemical impedance spectroscopy (EIS) tests during long-term immersion further demonstrate that Cu coating can provide an effective protection for NZ30K magnesium alloy from corrosion up to ∼60 h, due to its dense structure and a stable passive film formed. In addition, Cu coating exhibits good adhesion to substrate as confirmed by thermal shock test.
Transactions of Nonferrous Metals Society of China | 2008
Jian-Wei Chang; Xingwu Guo; Liming Peng; Wenjiang Ding; Ying-hong Peng
Abstract Anodization of rare earth-containing Mg alloy of Mg-3Nd-0.2Zn-0.4Zr (mass fraction, %) (NZ30K) was performed in composite electrolyte containing NaOH, KOH, K2SiO3, Na2SiO3, NaF, KF etc. The anodic coating was characterized by using X-ray diffraction(XRD), field emission electron scanning microscope(FE-SEM) and electron probe microscopic analysis(EPMA). The corrosion resistance of the anodized alloy and the substrate was evaluated in 5% NaCl solution using electrochemical impedance spectroscopy(EIS). The results of XRD show that the anodic coating is mainly composed of MgO. EPMA indicates that magnesium and oxygen are almost uniformly distributed across the coating, and the fluorine content decreases gradually from the interface of coating-substrate to the surface, whereas the distribution of silicon is reverse to that of fluorine. The results of EIS analysis shows that the anodic coating exhibits the superior corrosion resistance for NZ30K alloy.
Transactions of Nonferrous Metals Society of China | 2014
Can Sun; Xingwu Guo; Shaohua Wang; Jiacheng Guo; Wenjiang Ding
Abstract Electroless nickel plating on AZ91D substrate with a new and eco-friendly pretreatment process based on tuning an electrochemical homogeneous surface was investigated. The morphology, deposition process, chemical composition and microstructure of Ni–P coating were studied. It is indicated that β phases are selectively removed, producing a microstructural homogeneous surface and the subsequent uniform and compact Zn immersion layer. A defect-free and well adhesive Ni–P coating can be successfully obtained due to its uniform nucleation and growth based on such pretreatment. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) tests reveal that Ni–P coating could significantly improve the corrosion resistance of AZ91D substrate.
Corrosion Science and Protection Technology | 2014
Can Sun; Xingwu Guo; Shaohua Wang; Wenjiang Ding
A new environment-friendly homogenization pretreatment process was adopted for the electroless nickel plating on AZ91D magnesium alloy. Then, the morphologies, chemical composition and microstructure of the pretreated layer and the formed Ni-P coating were studied using scanning electronic microscopy(SEM), energy-dispersive X-ray spectroscopy(EDS) and X-ray diffraction spectroscopy(XRD). It was indicated that a dense Zn film formed on the substrate surface after the homogenization pretreatment, due to the selective removal of β phase during the processing.As the result, the subsequently formed Ni-P coating was uniform, compact and defect-free with P content around 7.0%, which was characterized as an amorphous matter by XRD. Potentiodynamic polarization and electrochemical impedance spectroscopy(EIS) tests revealed that the Ni-P coating could significantly improve the corrosion resistance of AZ91D magnesium alloy with an obvious positive shifting of corrosion potential by 1.136 V and a dramatic reduce of corrosion current density by two orders of magnitude. Furthermore the obtained Ni-P coating showed excellent adhesion to AZ91D substrate.
Electrochimica Acta | 2007
Jian-Wei Chang; Xingwu Guo; Peng-Huai Fu; Liming Peng; Wenjiang Ding
Electrochimica Acta | 2007
Xingwu Guo; Jian-Wei Chang; Shangming He; Wenjiang Ding; Xi-Shu Wang
Corrosion Science | 2008
Jian-Wei Chang; Xingwu Guo; Shangming He; Penghuai Fu; Liming Peng; Wenjiang Ding
Corrosion Science | 2011
Haiyan Yang; Xingwu Guo; Guohua Wu; Wenjiang Ding; N. Birbilis