Effects of Hot Isostatic Pressing on the Microstructure and Properties of Mg-Gd-Y-Zn Alloys

Hot isostatic pressing (HIP) treatment after solution treatment has been investigated on its effects on the mechanical and corrosion properties of Mg-Gd-Y-Zn alloys with high long-period stacking order (LPSO) 14H phase fractions. Plate and cylinder samples of three different compositions were cut from permanent mold castings. The alloy samples were solution treated for 25 h at 500 °C and processed with the following HIP conditions: 485–490 °C, 100–200 MPa, for 2 h. The mechanical properties generally increased with HIP. Under accelerated corrosion conditions (submersion in 3% KCl at a temperature of 90 °C), the corrosion rate was observed to increase after HIP. HIP was found not to change the density of the samples, indicating micro-porosity was not an issue. The change in corrosion rate and mechanical properties were a result of microstructural changes due to the HIP thermal cycle. CALPHAD (CALculation of PHAse Diagrams) modeling of the three compositions as well as scanning electron microscopy (SEM) microstructural observations of the alloys are provided.