The structure of complex Mg-Ag-R.E.-Th alloys

The magnesium-silver-rare earth system provides the best combination of room and elevated temperarure properties of all the magnesium casting alloys. Preliminary investigation had shown that small Th additions improved the room temperature properties of these alloys. Thus, the effect of the replacement of Nd by Th on the structure and properties was studied. Three alloys were examined in detail: Mg-2.5%Ag-0.5%Th-1.5%Nd-0.6%Zr; Mg-2.5%Ag-1%Th-1%Nd-0.6%Zr; Mg-2.5%Ag-1.5%Th-0.5%Nd-0.6%Zr. Zr is present as a grain refining constituent. The alloys were solution treated and then precipitation hardened at 250 deg C for various time. The ageing response and the metallographic examination of the alloys are presented