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Han P.H.,Shanghai University of Engineering Science | Xu Z.H.,Shanghai University of Engineering Science | Wang C.P.,Shanghai University of Engineering Science | Li M.C.,Shanghai University of Engineering Science | And 2 more authors.
International Journal of Electrochemical Science | Year: 2014

The cyclic method of hot exhaust gas-oxidation and condensates immersion has been adopted to simulate the internal service conditions of automotive mufflers. The condensation corrosion of 409 stainless steel was investigated during the immersion by using electrochemical measurement and surface analysis techniques. Due to the existence of defects, the oxidation and corrosion products layers on the specimen surfaces play an unimportant role in the condensate corrosion. During the cyclic processes, small pits will form gradually and result in relatively steady active corrosion for specimens in the condensate solutions. Trace SO2 in the hot exhaust gas only exerts slight inhibition on condensate corrosion through the initial oxidation process, but it almost has no influence on condensate corrosion anymore with the progress of cyclic process. The evolution of condensate corrosion is discussed in detail.© 2014 The Authors. Source


Feng W.,State Key Laboratory of Development and Application Technology of Automotive Steels | Wu Z.,Shanghai JiaoTong University | Wang L.,State Key Laboratory of Development and Application Technology of Automotive Steels | Speer J.G.,Colorado School of Mines
Steel Research International | Year: 2013

The effect of testing temperature on retained austenite (RA) stability of industrially cold rolled CMnSi sheet steel treated by quenching and partitioning (Q&P) process has been investigated by observing the deformation and transformation behavior of RA at different testing temperatures. Uniaxial tensile properties at different temperatures were determined and a correlation between RA stability and mechanical properties were also established. Ultimate tensile strength increases monotonously when temperature decreases, while total elongation reaches an optimum value between 0 and 20°C, where RA exhibits the greatest TRIP effect. Work hardening rate was calculated to decrease through three different stages in an oscillation manner, leading to significant enhancement in both strength and ductility. The kinetic of deformation-induced martensite transformation is also studied and the stability of RA can be evaluated by comparing the kinetic parameter β. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source


Sun J.,State Key Laboratory of Development and Application Technology of Automotive Steels | Sun J.,Shanghai JiaoTong University | Yan Q.,State Key Laboratory of Development and Application Technology of Automotive Steels | Gao W.,China Automotive Systems | And 2 more authors.
Materials and Design | Year: 2015

Dissimilar metals of AA6013 aluminum alloy and Q235 low-carbon steel of 2.5mm thickness were butt joined using a 10kW fiber laser welding system with ER4043 filler metal. The study indicates that it is feasible to join aluminum alloy to steel by butt joints when zinc layer was hot-dip galvanized at the steel's groove face in advance, and better weld appearance can be obtained at appropriate welding parameters. The joints had dual characteristics of a welding joint on the aluminum side and a brazing joint on the steel side. The smooth Fe2Al5 layer adjacent to the steel matrix and the serrated-shape FeAl3 layer close to the weld metal were formed at the brazing interface. The overall thickness of Fe-Al intermetallic compounds layers produced in this experiment were varied from 1.8μm to 6.2μm at various welding parameters with laser power of 2.85-3.05kW and wire feed speed of 5-7m/min. The Al/steel butt joints were failed at the brazing interface during the tensile test and reached the maximum tensile strength of 120MPa. © 2015 Elsevier Ltd. Source


Sun J.,State Key Laboratory of Development and Application Technology of Automotive Steels | Sun J.,Shanghai JiaoTong University | Huang J.,State Key Laboratory of Development and Application Technology of Automotive Steels | Huang J.,Shanghai JiaoTong University | And 2 more authors.
International Journal of Advanced Manufacturing Technology | Year: 2015

Butt joining of aluminum alloy to steel of 2.5 mm thickness was conducted by a 10-kW fiber laser with ER4043 filler metal. A sound joint with excellent front and back formation was obtained after treating the steel with an electro-galvanizing process. The zinc coating could markedly improve the wetting of weld metal on the bevel surface of the steel. Zinc-rich regions which were mainly composed of Al matrix and Al-Zn eutectic at the grain boundaries were formed. The brazing interface consisted of Fe2Al5 layer close to the steel and the FeAl3 layer adjacent to the weld metal. The weld metal was composed of α-Al solid solutions and Al-Si near eutectic phases. The mechanical strength of the joint depended on the area of the brazing interface. Maximum tensile strengths of 174.64 and 130.19 MPa were obtained for the joint with a bevel angle of 30° and 45°, respectively. The fracture surface presented a typical cleavage fracture mode. All the joints failed in the Fe2Al5 layer. © 2015 Springer-Verlag London Source


Sun J.,State Key Laboratory of Development and Application Technology of Automotive Steels | Sun J.,Shanghai JiaoTong University | Sun J.,Shanghai Key Laboratory of Materials Laser Processing and Modification | Yan Q.,State Key Laboratory of Development and Application Technology of Automotive Steels | And 5 more authors.
Materials and Design | Year: 2016

Butt joining of AA6061 aluminum alloy and Q235 low-carbon steel of 2.5mm thickness was conducted using laser welding-brazing method with ER4043 filler metal. An electro-galvanizing process of the steel was performed to obtain a zinc coating at the steel's bevel surface before welding. The brazing interface and the tensile strength of the joints were evaluated. The results showed that a sound butt joint between Al and steel was obtained, with the brazing interface consisted of zinc rich regions and a Fe-Al intermetallic (IMC) layer. The thickness and morphology of the IMC reaction layer were not constant but varied along the brazing interface. The morphology of the IMC reaction layer was more complex and the layer was thicker when a smaller bevel angle of the steel was used. All the joints fractured in the Fe2Al5 layer of the brazing interface. The tensile strength of the joints was mainly determined by the bonding area of the brazing interface, and average tensile strengths of 110MPa and 150MPa were achieved when bevel angles of 45° and 30° were used respectively. © 2015 Elsevier Ltd. Source

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