Abstract:Based on the pressure-controlled solid-state friction extrusion additive equipment, additive friction stir deposition (AFSD) process tests of AA7075-T6 were carried out to explore the effect of travel speed on the microstructure and mechanical properties of the deposited layer. The results show that well-formed and defect-free AA7075-T6 deposited specimens were fabricated at a spindle rotational speed of 300 r/min and travel speeds of 100 and 150 mm/min. The deposited area exhibits a fully dense and fine equiaxed grain microstructure. The average grain size is significantly reduced compared with that of the original feed rod (36.33±1.99 μm). Due to strong thermal-force coupling friction and extrusion, the recrystallization area fraction of the deposited area is more than 80%, while the hardness and tensile properties exhibit uniform distribution. As the travel speed increases from 100 mm/min to 150 mm/min, the hardness of the top of deposited layers increases from 120 HV to 141 HV, corresponding to 69.8% and 82.1% of that of the feed rod, respectively. The corresponding tensile strength along transverse direction increases from 416.5 MPa to 477.5 MPa, and the average elongation improves from 6.25% to 9.25%. However, the tensile strength of bottom deposited layers increases from 397.0 MPa to 414.0 MPa, and the average elongation increases from 11.5% to 12.25%. The largest tensile strength and elongation of deposited layers can reach 78.1% and 80.6% of those of the feed rod, respectively. The fracture mode of the deposited specimens is characterized by ductile fracture. This indicates that the increase in travel speed is favorable to the improvement of strength and plasticity of the AFSD-treated layers.