Experimental thermal analysis of friction stir processing

Despite the large number of studies that are being conducted to advance the friction stir processing (FSP) technology, the effects of FSP on various mechanical and microstructural properties are still in need for further investigations. In addition, correlations between FSP parameters, mechanical properties and microstructural characteristics are not yet well understood. Accurate correlations are needed for successful modeling and process optimization. It is established that the temperature generated during FSP plays an important role in determining the microstructure and properties of the processed sheet and defining the tool life. Process parameters must be carefully chosen to allow the generation of enough heat to soften the material while limiting significant grain growth. Accurate measurement of the temperature distributions during processing are essential to understand the complicated deformation and associated mechanisms and to allow for effective process optimization. In this work, a dual-band thermography approach is used to measure the temperature distributions of AA5052 sheet during FSP. The setup utilizes two infrared detectors, to neutralize the emissivity and the facial effects, with 30 Hz acquisition rate. The variation of temperature with process parameters and their correlation to the resulting microstructure are discussed.