Friction stir processing of a Zr-modified 2014 aluminium alloy

The mechanical and microstructural properties of a Zr-modified 2014 aluminium alloy resulting from friction stir processing were analysed. The sheets were processed parallel to the extrusion direction, the tensile mechanical properties were evaluated at room temperature in transverse and longitudinal direction respect to the processing one. Tensile tests were also performed at higher temperatures and different strain rates in the nugget zone, in order to analyse the superplastic properties of the recrystallized material and to observe the differences with the parent materials as a function of the strong grain refinement due to the friction stir process. The high temperature behaviour of the material was studied, in the parallel direction, by means of tensile tests in the temperature and strain rate ranges of 400–500 °C and 10−2 to 10−4 s−1, respectively. Scanning electron microscopy (field-emission gun) examinations were also carried out to investigate more closely the fracture surfaces of the specimens tested at different temperatures and strain rates. namic recrystallized structure of the material was observed by employing optical and electron microscopy. The room temperature and high temperature tensile properties of the heavily refined structure resulted optimal for superplastic deformation thanks to very high levels of strain to fracture and strain-rate sensitivity exhibited at high strain rate levels (10−2 s−1).