Browsing by Author "Guo, Shun"

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    Microstructural evolution and mechanical properties of maraging steel produced by wire + arc additive manufacture process
    (Elsevier, 2017-12-06) Xu, Xiangfang; Ganguly, Supriyo; Ding, Jialuo; Guo, Shun; Williams, Stewart W.; Martina, Filomeno
    Wire + arc additive manufacture is developed for producing large-scale metallic components. In this paper, maraging steel parts were produced, and the microstructure and mechanical properties were investigated. The microhardness and tensile strength of the as deposited alloy reduced from the bottom to the top due to the transient thermal cycling, which resulted in partial aging and non-uniform formation of intermetallic compounds along the building direction. Solutionizing, followed by 3 h aging, significantly reduced the microstructural heterogeneity and increased the mechanical properties by 24.7% through the formation of large amounts of finely distributed precipitates. The as deposited alloy possessed superior strength to the wrought alloy in solutionized condition but inferior to the later in aged condition, which was attributed to the less pronounced aging response of the low-angle columnar grains characterized microstructure and the presence of retained and reverted austenite.
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    Study on strengthening mechanism of Ti/Cu electron beam welding
    (Elsevier, 2017-02-20) Guo, Shun; Zhou, Qi; Peng, Yong; Xu, Xiangfang; Diao, Chenglei; Kong, Jian; Luo, TianYuan; Wang, Kehong; Zhu, Jun
    Welding-brazing method is widely used for dissimilar metals welding. However, it is becoming increasingly difficult to further improve the connection strength by controlling the formation of the transition layer. In this study, an innovative welding method referred to as adjacent welding was addressed, which greatly improved the tensile strength of Ti/Cu dissimilar joint. The strength of new joint could reach up to 89% that of copper base metal, compared to the use of a traditional welding-brazing method which strength coefficient is within the limit of 70%. In order to determine the strengthening mechanism of adjacent welding, optical microscopy, SEM, EDS and XRD were applied for the analysis of microstructure and phase structure. Furthermore, tensile strength was also tested. The results show that due to the process of remelting and reverse solidification of intermetallic compounds (IMCs) layer, a less complex and thinner IMCs layer was formed and TiCu (553 HV) with high embrittlement existing in the front of titanium substrate was changed into Ti2Cu (442 HV). Performances of joints were optimized by these changes. An interpretation module was presented for the mechanism.