Precipitation induced densification in a sintered Al–Zn–Mg–Cu alloy

It is demonstrated that slow cooling to 200 °C from a high sintering temperature (620 °C) reduces porosity in an Al–8Zn–2.5Mg–1Cu powder compact when compared to isothermal sintering at the higher temperature for a longer time. The reduction in porosity is attributed to shrinkage associated with removal of solute from the aluminium solid solution and heterogeneous precipitation of the η phase (MgZn2), particularly onto pore surfaces.