Microstructure And Mechanical Properties Of 5182 Al Alloy With Surface Mechanical Attrition Treatment

Through into the research of recent years, gradient nano-structured materials exhibited unique microstructure and excellent performance. Surface Mechanical Attrition Treatment(SMAT), as one of Surface nano-technology itself, can significantly improve the mechanical properties. SMAT can overcome the Surface performance defect of aluminum alloy, improve overall performance of materials,prolong the service life. Therefore, this work was carried out on 5182 aluminum alloys with two kinds of different grain size subjected to SMAT. Using electron backscatter diffraction(EBSD), X-ray diffraction(XRD), scanning electron microscopy(SEM), micro-hardness and uniaxial tensile test equipment systems study the characteristics of microstructure and mechanical properties of 5182 aluminium alloys with different grain size after SMAT.Here are the main conclusions:1. The microstructure aspects, fine grain(continuous casting and rolling) and coarse grain(traditional rolling) of 5182 aluminum alloy testing for X-ray diffraction,the calibration results of the X-ray diffraction graph show that Al single-phase alloy only can be found in the fine grain and coarse grain of 5182 aluminum alloy before and after SMAT. Moreover, the crystal plane(111),(200),(220),(311) and(222)owned by the face-centered cubic structure can be found and the 5182 aluminum alloy of fine grain and coarse grain presented the stronger crystal(111) and(200)after SMAT. After SMAT for 1 min, the 5182 aluminum alloys of fine grain and coarse grain minimize the surface average grain size to 65.7 nm and 70.1 nm,respectively. The corresponding micro-strain were 0.17 % and 0.15 %.For the EBSD analysis of 5182 aluminum alloys with fine grain and coarse grain,the results show that 5182 aluminum alloys of the fine grain and coarse grain after SMAT treatment, the average grain size of alloy surface have a very large degree of refinement. Without SMAT, the average grain size of aluminium alloy 5182 with fine grain and coarse grain is 7 and 13μm, respectively. After SMAT for 3 min, the 5182 aluminum alloy of fine grain and coarse grain obtained the surface nanometer crystal(~ 100 nm) layer of 20 μm and 10 μm, respectively. Otherwise, the average grain size decreased to 5.6 μm and 12.5 μm, reduced by 24 % and 24 % comparing to the original samples, respectively. And, after SMAT, a gradient nano structure from the surface to the core of material was generated in the the 5182 aluminum alloys of fine grain and coarse grain. At the same time, we can see that the grains along the rolling direction were significantly elongated for the 5182 aluminum alloy of fine grain.However, the 5182 aluminum alloy of the coarse grain, the grain variation of rolling direction is relatively small, which indicates that continuous casting and rolling of5182 aluminum alloy is more efficient to generate the anisotropic than the traditional rolling. After SMAT for 3 min, the misorientation of 5182 aluminium alloy with fine grain and coarse grain is affected, making large angle grain boundary transform into the low angle grain boundary.2.Mechanics performance, for the aluminium alloy 5182 with fine grain and coarse grain after SMAT, the overall hardness of plate rised to a certain degree, and along the direction of plate specimen surface to the core formed the gradient descent state. Without SMAT, the hardness of 5182 aluminum alloys exhibited uniform distribution along the thickness direction. The hardness of 5182 aluminum alloy with fine grain after SAMT about 100μm depth from alloy surface is the highest and the micro-hardness increased from 76 Hv to 94~103 Hv. The 5182 aluminum alloy of coarse grain after SMAT within about 80μm gained the highest hardness and micro hardness increased from 74 HV to 93~103 Hv. With the increase of SMAT time, the hardness of plate also increased. A the same time, the hardness variation of 5182 aluminum alloys with the fine grain and coarse grain is similar before and after SMAT.At the same time, SMAT can improve the yield strength and the ultimate tensile strength of the alloy are significantly increased, but with a decrease in fracture elongation. As compared to the as-received fine-grained and coarse-grained 5182 Al alloy, the SMATed one exhibits 87.6 % and 82.2 % higher yielding strength after SMAT for 3min,respectively. However, with the increase of SMAT duration, the improvement of yield strength becomes lesser. However, the fine-grained and coarse-grained 5182 Al alloy retains respectable ductility; It was mainly attributedto its good strain harden behavior. Therefore, the different grain size 5182 Al alloy subjected to SMAT exhibits good strength- plasticity.In addition, we can find the fine-grained 5182 Al alloy exhibits a quite similar strain hardening behavior with the coarse-grained 5182 Al alloy. As compared to the as-received Al alloy, the SMATed one exhibits different strain hardening behavior. In the hardening stage II, the SMATed 5182 Al alloy shows a lower strain hardening rate and the strain hardening rate decreases with the increasing duration of SMAT process.In the hardening stage III, the SMATed 5182 Al alloy shows a higher strain hardening rate and the strain hardening rate increases with the increasing duration of SMAT process. While, the SMATed 5182 Al alloy shows a lower strain hardening rate and the strain hardening rate decreases with the increasing duration of SMAT process in the stage IV. At the same time, SMAT process 3min, and the strain hardening exponent strain hardening alloys can be only a slight decline. The SMATed 5182 Al alloy shows a lower strain hardening exponents and strain hardening exponents decreases with the increasing duration of SMAT process. Strain hardening capacity is the similar as strain hardening exponents, and strain hardening exponents and strain hardening capacity slightly decreases after SMAT for 3min...