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Residual Stress Measurement Using X-ray Diffraction in Friction Stir-Welded Dissimilar Titanium Alloys.
1Mechanical Engineering, School of Engineering, Wentworth Institute of Technology, Boston, MA 02115, USA.
Materials (Basel, Switzerland)
|April 13, 2024
Summary
Friction stir welding of dissimilar titanium alloys creates tensile residual stresses, particularly at the weld nugget. Stress levels are influenced by tool rotation and traverse speeds, showing an asymmetric pattern.
Area of Science:
- Materials Science
- Mechanical Engineering
- Metallurgy
Background:
- Surface residual stresses critically impact welded joint properties like fatigue resistance and fracture toughness.
- Joining dissimilar titanium alloys offers synergistic property combinations for advanced applications.
- Friction stir welding (FSW) is an effective solid-state joining technique for titanium alloys.
Purpose of the Study:
- To assess macroscopic surface residual stresses in dissimilar titanium alloys (Ti-6242 SG and Ti-54M) joined by friction stir welding.
- To investigate the influence of tool rotation and traverse speeds on residual stress distribution.
- To understand the effect of grain refinement and distortion in the stir zone on residual stresses.
Main Methods:
- Friction stir welding of Ti-6242 SG and Ti-54M dissimilar alloys.
- X-ray diffraction (XRD) for residual stress measurement, assuming linear lattice distortion.
- Application of the sin²φ method using LEPTOS® (v7.8) software.
- Quantification of stresses at the surface and 1.5 mm depth within a 1x1 mm² cross-section.
Main Results:
- Tensile residual stresses were observed at the weld boundaries and within the stir zone.
- Approximately 50 MPa of tensile stress was measured at the weld nugget center under specific low-speed conditions.
- Residual stress values exhibited asymmetry and were influenced by varying tool rotation and traverse speeds.
Conclusions:
- FSW of dissimilar titanium alloys results in tensile residual stresses that are sensitive to process parameters.
- The distribution of residual stresses is complex, influenced by material interfaces and welding conditions.
- Understanding these stresses is crucial for predicting the performance of dissimilar titanium alloy joints.
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