Dissimilar friction stir welds in AA5083-AA6082. Part II: Process parameter effects on microstructure

The aim of this study is to explore the bounds of the so-called processing window, within which good-quality welds can be produced, for the friction stir welding of AA5083 to AA6082 using a systematic set of rotation and traverse speeds. The first paper in this series examined the thermal and macroscopic aspects. In this paper, several microstructurally related characteristics, including hardness, grain size, and precipitate distribution, have been examined in greater detail. The observed variations are correlated and contrasted with the observed and predicted thermal distributions. In addition, the thermal model developed in part I has been coupled to hardness models based on classical isothermal aging studies for each alloy to predict the hardness variations across the welds.