Characterization of the microstructure, mechanical properties, and shot peening response of an industrially processed Al-Zn-Mg-Cu PM alloy

The objective of this study was to characterize the mechanical/physical properties of an industrially processed Al-Zn-Mg-Cu powder metallurgy (PM) alloy and assess the subsequent effects of shot peening. The research involved a number of experimental techniques, including density measurements, tensile testing, Rockwell hardness measurements, nano-indentation, and optical and scanning electron microscopy. Residual stress measurements were completed using a combination of X-ray diffraction (XRD) and neutron diffraction (ND). Industrially produced specimens attained near full theoretical density and exhibited a nominal yield strength on the order of 460 MPa in the T6 condition. It was discovered that zinc had preferentially evaporated from the surface of the components during sintering. The depleted region persisted to a depth of ≈3 mm and resulted in reduced nano-hardness of 1.65 GPa at the surface versus 2.50 GPa in the bulk. Shot peening increased the surface hardness of the alloy and resulted in a peak compressive residual stress of 232 MPa at the treated surface.