Microstructure and mechanical properties of 7B85 alloy ultrasonic rolling treated 7B85 alloy

The 7B85 alloy was treated by ultrasonic rolling treatment (USRT) with different preloading depth (0, 0.1, 0.2, 0.3 and 0.4 mm). The microstructure and mechanical properties of 7B85 alloy treated by ultrasonic rolling were investigated by optical microscope, surface roughness tester, micro Vickers hardness test, tensile test, scanning electron microscope, X-ray diffraction and electron back scattering diffraction. The results show that the surface roughness, microhardness and tensile strength of 7B85 alloy treated by ultrasonic surface rolling reached the optimal value, when the preloading depth was 0.2 mm. The fracture morphology of the 7B85 alloy showed a large number of deep dimples, which were mainly in the form of ductile fracture. Meanwhile, most of the η precipitates in the 7B85 alloy are dissolved into the aluminum matrix after USRT, and the average grain size of the alloy surface is about (25.22 ± 6.46) nm. The improvement of the mechanical properties of the 7B85 alloy after USRT is mainly attributed to the joint action of fine grain strengthening and stress strengthening on the alloy surface.