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首页> 外文学位 >Effect of alloying on microstructure and precipitate evolution in ferritic weld metal.
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Effect of alloying on microstructure and precipitate evolution in ferritic weld metal.

机译：合金化对铁素体焊缝金属组织和析出物的影响。

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摘要

The effect of alloying on the microstructure of ferritic weld metal produced with an self-shielded flux cored arc welding process (FCAW-S) has been studied. The welding electrode has a flux core that is intentionally alloyed with strong deoxidizers and denitriding elements such as aluminum, titanium and zirconium in addition to austenite formers such as manganese and nickel. This results in formation of microstructure consisting of carbide free bainite, retained austenite and twinned martensite. The work focuses on characterization of the microstructures and the precipitates formed during solidification and the allotropic phase transformation of the weld metal. Aluminum, manganese and nickel have significant solubility in iron while aluminum, titanium and zirconium have very strong affinity for nitrogen and oxygen. The effect of these alloying elements on the phase transformation and precipitation of oxides and nitrides have been studied with various characterization techniques. In-situ X-ray synchrotron diffraction has been used to characterize the solidification path and the effect of heating and cooling rates on microstructure evolution. Scanning Transmission Electron Microscopy (STEM) in conjunction with Energy Dispersive Spectroscopy (EDS) and Electron energy loss spectroscopy (EELS) was used to study the effect of micro-alloying additions on inclusion evolution. The formation of core-shell structure of oxide/nitride is identified as being key to improvement in toughness of the weld metal. Electron Back Scattered Diffraction (EBSD) in combination with Orientation Imaging Microscopy (OIM) and Transmission electron microscopy (TEM) has been employed to study the effect of alloying on austenite to ferrite transformation modes. The prevention of twinned martensite has been identified to be key to improving ductility for achieving high strength weld metal.
机译：研究了合金化对采用自保护药芯焊丝电弧焊工艺（FCAW-S）生产的铁素体焊缝金属组织的影响。焊接电极的焊剂芯除奥氏体形成剂（如锰和镍）外，还特意与强脱氧剂和反氮化元素（如铝，钛和锆）合金化。这导致形成由无碳化物的贝氏体，残余奥氏体和孪晶马氏体组成的微观结构。这项工作着重于在焊接金属的凝固和同素异形相变过程中形成的微观结构和析出物的表征。铝，锰和镍在铁中具有显着的溶解性，而铝，钛和锆对氮和氧具有非常强的亲和力。已经通过各种表征技术研究了这些合金元素对氧化物和氮化物的相变和沉淀的影响。原位X射线同步加速器衍射已用于表征凝固路径以及加热和冷却速率对组织演变的影响。扫描透射电子显微镜（STEM）结合能量色散谱（EDS）和电子能量损失谱（EELS）用于研究微合金化添加剂对夹杂物演化的影响。氧化物/氮化物核-壳结构的形成被认为是提高焊接金属韧性的关键。电子背散射衍射（EBSD）与定向成像显微镜（OIM）和透射电子显微镜（TEM）的结合已用于研究合金化对奥氏体到铁素体转变模式的影响。业已确定，防止孪晶马氏体是提高延展性以获得高强度焊接金属的关键。

著录项

  • 作者

    Narayanan, Badri Kannan.;

  • 作者单位

    The Ohio State University.;

  • 授予单位 The Ohio State University.;
  • 学科 Engineering Materials Science.
  • 学位 Ph.D.
  • 年度 2009
  • 页码 205 p.
  • 总页数 205
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 工程材料学;
  • 关键词

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