Microstructures Evolution And Mechanical Properties Of 5052 Alloy With Gradient Structure

Gradient materials have attracted much attention because of the possibility to overcome the trade-off between strength and ductility.In this study,the RASP(Rotation Accelerated Shot Peening)equipment was used to obtain gradient structures in 5052 Al-Mg alloy.Firstly,microstructure evolution along the thickness of 5052 Al-Mg alloy was analyzed after RASP treatment.Secondly,the effects of RASP parameters,including RASP duration,RASP speed,RASP temperature,and sample thickness,on the mechanical properties of 5052 Al-Mg alloy were discussed,respectively.Finally,the influence of Co-rolling treatment on the mechanical behavior of 5052 Al-Mg alloy was studied.The main conclusions are as follows:(1)Nano-grains,equiaxed sub-grains and elongated sub-grains were formed in the surface of 5052 Al-Mg alloy processed by RASP along the cross-section.And the dislocation configuration mainly consists of DTs(dislocation tangles),DWs(dislocation walls)and DCs(dislocation cells),and DCs size changes along the thickness.(2)The effect of RASP dutation on the mechanical properties can be concluded that the increase of RASP duration increases the YS(yield strength)while the ductility decreases,and the YS reaches the maximum value of 180 MPa at the condition of 50 m/s-10 min.The influence on the microhardness distribution is as follows:when the RASP speed is below 40 m/s,the microhardness distribution curve moves up as a whole with the duration increase;when the RASP speed is above 40 m/s,the increase of duration makes the microhardness values intertwined near the surface,but increase near the core.With the increase of RASP speed,the YS increases linearly while uniform elongation(?u)decreases linearly,and the thickness of the gradient layer is changed.(3)Cryogenic-RASP treatment suppressed dislocations' movement when compared to room temperature RASP,which leads to lower microhardness.But the YS is higher because of precipitated phases.It is found that the synergetic strengthing by gradient structure is the most significant when the volume fraction of gradient structures is about 0.5,which is helpful to obtain high strength and ductility simultaneously.(4)Co-rolling treatment makes the YS improved greatly and ?u decreased drastically,a small increase of YS and ?u was found in the samples left with gradient structure.