Evaluation of the residual stress and microstructure of extruded and shot peened aluminum alloy 6082

Abstract

Aluminum-magnesium-silicon alloys have been widely used as extruded products due to its mechanical strength and high ductility. The effects induced by shot peening has been extensively used in materials that have potential for structural applications. In this context, the purpose of this study was to evaluate the residual stress induced by shot peening of extruded aluminum alloy 6082. Initially, the effect of heat treatments such as solution treatment and ageing of this alloy was studied. The residual stress measurements were carried out using x-ray diffraction. The microstructure of the alloy was studied by optical microscopy. The crystallographic texture was determined using x-ray diffraction and back-scattered electron diffraction. The heat treatment sequence that resulted in the highest hardness of Al alloy 6082 was solution treatment at 560ºC for 30 min, followed by ageing at 185ºC for 5 h. The residual stress in compression of the extruded alloy’s surface increased by 87.38%, from -66.6 to -124.8 MPa, caused by shot peening. The residual stress profile indicated an increase in its value up to a depth of 86 μm, beyond which the values obtained were unreliable. The extruded section revealed accentuated crystallographic texture in the (111) plane parallel to the cross-section and in the (200) and (220) planes oriented preferentially in the longitudinal direction to extrusion and perpendicular to the (111) plane.