Thermomechanical deformation behaviour of DH36 steel during friction stir welding by experimental validation and modelling

Abstract

Friction stir welding is a solid state thermomechanical deformation process from which the plasticisation behaviour of the stirred material can be evaluated through the study of flow stress evolution. Flow stress data also supporting the development of a local microstructural numerical model have been generated. Hot compression testing of DH36 steel has been performed at a temperature range of 700–1100°C and strain rates from 10⁻³ to 10² s⁻¹ to study the alloy’s thermomechanical deformation behaviour in conditions that simulate the actual friction stir welding process. It has been found that the evolution of flow stress is significantly affected by the test temperature and deformation rate. The material’s constitutive equation and constants have been calculated after analysis of these data. Preliminary numerical analysis results are in good agreement with experimental observations.

Keywords:

• Friction stir welding
• Thermomechanical deformation
• Flow stress
• Low alloy steel
• Simulation
• Modelling

Acknowledgements

The authors gratefully acknowledge the financial support of the European Union, which has funded this work as part of the Collaborative Research Project HILDA (High Integrity Low Distortion Assembly) through the Seventh Framework Programme (grant no. SCP2-GA-2012-314534-HILDA).