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

Friction stir welding is a solid state thermo-mechanical deformation process from which the plasticisation behaviour of the stirred material can be evaluated throuh 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 700ºC-1100ºC and strain rates from 10-³ s-¹ to 10² s-¹ to study the alloy's thermo-mechanical deformation behaviour in conditions which 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.