Effect of pre-rolling temperature on microstructures, tensile properties and fracture behaviors of Al-5.9Zn-1.9Mg alloy during thermomechanical treatment

Abstract

The microstructures, mechanical properties, and fracture behaviors of an Al-5.9Zn-1.9Mg alloy subjected to thermomechanical treatment across different pre-rolling temperatures have been exhaustively investigated in present work. The pre-deformation temperature exerts a modest influence on grain morphology, while it profoundly impacts the dislocation configurations and precipitation behaviors. Elevating the rolling temperature from ambient to 170 °C result in a reduction in dislocation density within grains accompanied by a notable enhancement in their distributional uniformity. While advancing the temperature to 320 °C prompts the premature formation of precipitates during deformation, which diminishes the precipitation during the subsequent ageing. Tensile results reveal that the thermomechanical treatment incorporating pre-rolling at 170 °C confer a substantial strengthening effect on the alloy on the basis of both grain boundary strengthening and dislocation strengthening stemmed from pre-deformation along with the precipitation strengthening generated by ageing. Furthermore, the microstructure exhibits a relatively scarce presence of inhomogeneous features such as dislocation pile-ups and micro shear bands, contributing favorably to enhance the ductility of the alloy that present the mixture of cleavage fracture and dimple-induced failure.

Keywords

Al-Zn-Mg alloy / thermomechanical treatment / deformation temperature / microstructures / tensile properties

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