Characterization of extruded Mg-Dy-Nd under stress corrosion in C-Ring tests
This study focuses on the characterization of the failure behavior of extruded Mg-10Dy-1Nd alloy under stress corrosion. The binary alloys Mg10Dy and Mg1Nd are compared to the ternary alloy system regarding microstructure, hardness, strength and corrosion behavior. The ternary alloy Mg-Dy-Nd has not fully recrystallized, but reveals the highest strength and hardness. These investigated alloys twin under plastic deformation. Static C-Ring tests in Ringer solution are used to evaluate the stress corrosion properties. Furthermore, the C-Ring specimen were subjected to compressive loading until fracture. Whereas Mg1Nd shows a ductile behavior, the alloys containing Dy fractured at the crack‐opening tensile side. The crack initiation and growth is mainly influenced by twin boundaries. The inhomogeneous microstructure in Mg10Dy1Nd causes lower fracture toughness compared to Mg10Dy. Hydrogen assisted fracture cannot be excluded. Under static stress corrosion none of the alloys failed by fracturing, but corrosion pits formed to different extents. Even adding Nd causes lower fracture toughness, it reduces the grain size and has a positive influence on the corrosion rate. Corrosion pits are shaped elliptical and subsurface. Even some of them reduced the remaining wall thickness significantly, but the stress increase because of the notch effect did not lead to crack initiation.