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Qianjin, China

Cui C.Y.,Jiangsu University | Cui X.G.,Jiangsu University | Ren X.D.,Jiangsu University | Liu T.T.,Jiangsu University | And 2 more authors.
Materials and Design | Year: 2013

The butt welding of 304 stainless steel plates with thickness of 3. mm and 6. mm were achieved by YLR-6000 fiber laser under Ar protective gas. The weld appearance, microstructure, composition distribution and microhardness of welded joint were emphatically investigated. The results showed that the narrow and fully penetrated welded joint without marco-defects can be obtained with tightly focused 2. kW fiber laser power and 20. mm/s welding speed. The weld bead was smooth, and various microstructures typically formed at different zones of the welded joint. The fine columnar and equiaxed crystals existed in the edge and center of weld bead, respectively. Both were different with the microstructure of the stainless steel substrate. However, the composition distribution of the welded joint had no obvious changes. Furthermore, the superior microhardness of welded joint over the stainless steel substrate was mainly attributed to its finer microstructure. © 2013 Elsevier Ltd.

Cui X.G.,Jiangsu University | Cui C.Y.,Jiangsu University | Cheng X.N.,Jiangsu University | Xu X.J.,Jiangsu University | And 3 more authors.
Materials Science and Engineering A | Year: 2010

Experiments were conducted to study the microstructure and tensile properties of the sub-micro and nano-structured Al produced by the Nd:YAG pulsed laser surface melting (LSM). The surface and longitudinal section microstructures of the Al samples after LSM were analyzed. The solidification microstructures in the LSM region were very fine which was beneficial to improve the properties of the Al sample. The tensile behavior and the relevant fracture mechanism of the LSM layer on the Al surface were investigated based on the analyses of the tensile test results. The fracture morphologies in the LSM region were small and shallow dimples with the size of 0.4-1μm. It indicated that the Al sample showed the ductile behavior because the grains were refined effectively after LSM. Furthermore, the typical amorphous fracture morphology with the fish scale structure was also obtained at the strain rate of 1.0×10-4s-1 after LSM with the laser power density of 3.65×109W/m2. © 2010 Elsevier B.V.

Cui C.Y.,Jiangsu University | Cui X.G.,Jiangsu University | Ren X.D.,Jiangsu University | Qi M.J.,Jiangsu University | And 2 more authors.
Applied Surface Science | Year: 2014

Surface oxidation phenomenon of AISI 304 stainless steel induced by Nd:YAG pulsed laser in air was investigated using scanning electron spectroscopy (SEM), high resolution transmission electron microscope (HRTEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The results showed that there were different morphologies and phase compositions in one laser spot from the center to the edge on stainless steel surface after pulsed laser oxidation. The morphologies were mainly nano-spheres and hexagons. It was proved using XRD that they were basically γ-Fe, Cr2O3, Fe 2O3 and a small amount of MnO2. The elemental compositions in the edge region were rich in Cr and deficient in Fe, while it had an opposite distribution trend in the center of the laser spot. XPS measurement confirmed the formed oxides on the stainless steel surface, indicating that most of the elements were in oxidation states. Moreover, the oxidation behavior of the stainless steel in one laser spot was assessed using thermodynamics and kinetics of laser oxidation process. And the oxidation mechanism was also clearly revealed. © 2014 Elsevier B.V.

Cui C.Y.,Jiangsu University | Cui X.G.,Jiangsu University | Zhao Q.,Jiangsu University | Hu J.D.,Jilin University | And 2 more authors.
Optics and Laser Technology | Year: 2012

Different surface morphologies on AISI 304 stainless steel have been obtained after millisecond Nd:YAG pulsed laser oxidation. The effects of laser processing parameters, especially pulse width and laser energy density on the surface morphologies of the stainless steel were emphatically investigated. The results showed that surface morphologies were significantly changed with increasing laser pulse widths and laser energy densities. When the pulse width was 0.21.0 ms and laser energy density was 4.30×10 67. 00×10 6 J/m 2, the surface was obviously damaged and the morphologies varied gradually from craters to ripple structures. However, when the pulse width was longer than 1 ms and the laser energy density was increased from 1.90×10 7 to 3.16×10 7 J/m 2, the sizes of craters got smaller until disappeared and the surface became flatter and smoother. Nevertheless, the smooth surface was not obtained under overhigh laser energy densities. In addition, the schematic relationship was used to describe the formation process and mechanism of different surface morphologies. © 2011 Elsevier Ltd. All rights reserved.

Cui C.Y.,Jiangsu University | Xia C.D.,Jiangsu University | Cui X.G.,Jiangsu University | Cui X.G.,Zhejiang University | And 3 more authors.
Journal of Alloys and Compounds | Year: 2015

Novel morphologies of chromium sesquioxide (Cr2O3) were successfully formed on AISI 304 stainless steel surface by Nd: YAG pulsed laser oxidation in air. The obtained Cr2O3 presented mainly dendritic, gear-like, flower-like and regular hexagonal morphologies with sizes from hundred nanometers to several micrometers. These various morphologies chiefly originated from two groups of diverse growth directions within (0 0 0 1) basal plane, i.e., ¯21¯1¯0¯ and ¯011¯0¯ directions. The preferential growth along different directions determined the final Cr2O3 morphologies. And the crystallographic analyses basically accorded with the experimental results. Moreover, the growth mechanism of the hexagonal Cr2O3 was analyzed in detail from its morphology evolution, and a corresponding growth model was reasonably proposed. © 2015 The Authors.

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