Residual stresses, microstructure and tensile properties in Ti–6Al–4V friction stir welds

Abstract

This paper reports the results of a systematic investigation of residual stresses as a function of welding speed in a set of Ti–6Al–4V friction stir welds. The investigation focuses on residual stress but links these data with microstructural information derived from micrographs and hardness measurements as well as mechanical testing results. Residual stresses were determined using energy dispersive synchrotron X-ray diffraction, which allows phase specific stresses to be distinguished. The data presented in this paper demonstrate that welds with high tensile properties can be obtained, which also have relatively low peak tensile residual stress values of ∼30% of the tensile strength. The data also show a clear correlation between heat input and the width of the residual stress profile.

Keywords:

• Residual stress
• Ti–6Al–4V
• Titanium
• Friction stir weld
• Microstructure
• Synchrotron X-ray diffraction

The authors acknowledge the European Synchrotron Radiation Facility for access to beam time through experiment MA-856 as well as the technical support of beam line staff on ID15A in the preparation of the experiment. Financial support from the South African National Research Foundation (NRF) with grant no. IRDP-62341 is also acknowledged for one of the authors (DGH). In addition, Dr M. Attallah (University of Birmingham, UK) is gratefully acknowledged for assistance with the discussion on elastic properties of Ti alloys.