Effects of wet shot peening on microstructures and mechanical properties of a 2060-T8 aluminum-lithium alloy

In this work, wet shot peening (WSP) was investigated to modify the microstructures and mechanical properties of a 2060-T8 aluminum-lithium (Al-Li) alloy through numerical and experimental methods. Gradient distribu-tions of plastic strain and strain rate induced by WSP were obtained from simulation via coupled Eulerian-Lagrangian method and fitted by exponential functions. They were the primary extrinsic factors determining microstructural evolution and deformation mechanisms. In parallel, the hardening behaviors and heterogeneous microstructures in the modified layer with a thickness of about 200 mu m were characterized by experiments. Experimental results showed that WSP improved yield strength, tensile strength and the microhardness at surface respectively by 16.15%, 11.83% and 10%, but the total elongation was reduced by 30.18%. The significant improvement of strength was associated with the combined influences of nanocrystalline, severe lattice distor-tion, precipitates variation, dense dislocations and stacking faults. Moreover, the gradient hierarchical micro-structures fabricated by the non-uniform deformation of WSP can promote the accumulation of geometrically necessary dislocations (GNDs). The corresponding back stress caused by GNDs would produce extra hardening effects. Consequently, a modified composite model considering various microstructures, the volume fractions of modified layers as well as material continuity was proposed to predict the mechanical properties of materials processed by surface treatments. The estimated yield strength was found to agree well with experimental results.

Automated summary

In this study, wet shot peening (WSP) was used to modify the microstructures and mechanical properties of an aluminum-lithium (Al-Li) alloy. Numerical simulation and experimental methods were employed to investigate the effects of WSP. The results showed that the gradient distributions of plastic strain and strain rate induced by WSP were the primary factors determining the microstructural evolution and deformation mechanisms. Experimental characterization revealed that WSP significantly improved the yield strength, tensile strength, and microhardness of the alloy, but reduced its total elongation. The non-uniform deformation of WSP also resulted in a gradient hierarchical microstructure that promoted the accumulation of geometrically necessary dislocations, leading to extra hardening effects.