Dispersoid particles precipitated during the solutionizing course of Al-12 wt%Si-4 wt%Cu-1.2 wt%Mn alloy and their influence on high temperature strength

Microstructure evolution during the solutionizing course of Al-12 wt%Si-4 wt%Cu-1.2 wt%Mn alloy was characterized by XRD and TEM-SAD (selected area diffraction), and the contribution of dispersoid Mn-rich precipitates to high temperature strength is discussed qualitatively. Fine and dispersoid Al20Cu2Mn3 (orthorhombic structure, a=2.34 nm, b=1.32 nm, c=0.75 nm) and Al15Mn3Si2 (body center cubic structure, a=2.259 nm) particles are found to precipitate during the solutionizing course. Both the solutionizing temperature and time have an important influence on the precipitation behavior of these particles. The number density of the precipitates first increased and then decreased with the solutionizing temperature. It decreased monotonically with the solutionizing time. The variation trend of the size of precipitates with temperature and time was opposite to that of the number density. The precipitation of these dispersoid Al20Cu2Mn3 and Al15Mn3Si2 particles has a considerable influence on the high temperature strength.