Journal of the Korean Society for Heat Treatment (열처리공학회지)

The Korean Society for Heat Treatment (한국열처리공학회)
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Microstructure and Mechanical Properties of Pure Titanium Processed using Friction Stir Welding

순수 타이타늄의 기계적 특성에 미치는 마찰 교반 용접 공정 조건의 영향

  • Lee, Y.J. (Materials Science and Metallurgical Engineering, Sunchon National University) ;
  • Choi, A. (Materials Science and Metallurgical Engineering, Sunchon National University) ;
  • Lee, S.J. (Joining and Welding Research Institute, Osaka University) ;
  • Fujii, Hidetoshi (Joining and Welding Research Institute, Osaka University) ;
  • Shin, S.E. (Materials Science and Metallurgical Engineering, Sunchon National University) ;
  • Lee, D.G. (Materials Science and Metallurgical Engineering, Sunchon National University)
  • 이용재 (순천대학교 신소재공학과) ;
  • 최안드레 (순천대학교 신소재공학과) ;
  • 이승준 (오사카대학교 용접접합연구소) ;
  • ;
  • 신세은 (순천대학교 신소재공학과) ;
  • 이동근 (순천대학교 신소재공학과)
  • Received : 2019.05.10
  • Accepted : 2019.05.24
  • Published : 2019.05.30
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Abstract

Friction stir welding is one of the interesting welding methods for titanium and its alloy which proceeds with plastic flow due to thermo-mechanical stirring and friction heat. Solid-state welding can solve severe problems such as high-temperature oxidation, interstitial oxygen diffusion and grain coarsening by liquid-state welding. Dynamic recrystallization and grain refinement can vary significantly with the plunging load and rotational speed of tool during friction stir welding, and suitable process conditions must be optimized to obtain microstructure and better mechanical characteristics. Suitable FSW conditions were 1000 kg of plunging load and 200 rpm of rotational speed and it showed YS 270 MPa, UTS 332.1 MPa, and El 17.3%, which were very similar to those of wrought titanium sheet.

Keywords

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Fig. 1. Schematic image of FSW process.

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Fig. 2. OM images of the welded joint for each samples; (a), (b) Sample 1, (c), (d) Sample 2, and (e), (f) Sample 3. (a), (c), (e) BM, and (b), (d), (f) TMAZ of the samples.

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Fig. 3. SEM images of the SZ region for each samples;(a) Sample 1, (b) Sample 2, and (c) Sample 3.

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Fig. 4. Vickers hardness profiles on the cross-section of the welded zone according to welding conditions.

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Fig. 5. Fractography of the FSWed samples after tensile test; (a)-(c) Sample 1, (d)-(f) Sample 2, and (g)-(i) Sample 3.

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Fig. 6. Observation of DIC during tensile testing of the FSWed samples.

Table 1. FSW conditions of different samples

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Table 2. Tensile properties of the FSWed samples

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