Characterization of an Extruded Mg-Dy-Nd Alloy during Stress Corrosion with C-Ring Tests

Abstract

This study focuses on the characterization of the failure behavior of an extruded Mg10Dy1Nd alloy during stress corrosion. The microstructure, hardness, strength and corrosion behavior of binary alloys Mg10Dy and Mg1Nd are compared to those of the ternary alloy system. The ternary alloy Mg-Dy-Nd that is not fully recrystallized has the highest hardness but lacks ductility. The investigated alloys twin during plastic deformation. Static C-ring tests in Ringer solution were used to evaluate the stress corrosion properties, and stress corrosion could not be found. None of the alloys failed by fracturing, but corrosion pits formed to various extents. These corrosion pits were elliptical in shape and located below the surface. Some of the pits reduced the remaining wall thickness significantly, but the stress increased by the notch effect did not lead to crack initiation. Furthermore, the C-ring specimen was subjected to compressive loading until fracture. Whereas the Mg1Nd alloy showed ductile behavior, the alloys containing Dy fractured on the tensile side. The crack initiation and growth were mainly influenced by the twin boundaries. The Mg10Dy1Nd alloy had an inhomogeneous microstructure and low ductility, which resulted in a lower fracture toughness than that of the Mg10Dy alloy. There were features that indicate hydrogen-assisted fracture. Although adding Nd decreased the fracture toughness, it reduced the grain size and had a positive influence on the corrosion rate during immersion testing.

Crack Propagation in As-Extruded and Heat-Treated Mg-Dy-Nd-Zn-Zr Alloy Explained by the Effect of LPSO Structures and Their Micro- and Nanohardness

“…This study applies a C-ring compression test to investigate the fracture toughness and crack propagation. Similar tests have already been done on the Mg-Dy-Nd alloy [37]. Dislocations in twinned regions or grains with lamellae LPSO structures will have short distances to move and will therefore pile up at these obstacles and can lead to crack initiation and reduced toughness [38].…”

“…C-ring samples with a width of 10 mm were machined from the extruded tubes with an outer diameter of 34 mm and a wall thickness of 2 mm. Their position in the initial extruded tubes can be seen in [37]. C-ring samples were compressed at 2 mm/min in a testing machine up to fracture in Ringer solution at 37 • C. The study on Mg-Dy-Nd [37] provides detailed information on the C-ring compression test in Ringer and the study in [26] presents data from the force-displacement curves, such as force and displacement at crack initiation and its fracture toughness.…”

Magnesium Alloys for Biomedical Applications

“…Four research articles and one review paper have been published in this Special Issue of Metals. The subjects cover studies on corrosion behavior and its characterization in in-vitro environments [1][2][3] and in vivo studies on facial reconstruction [4,5]. Mainly Al-free alloys, Mg-Gd [1], Mg-Zn-Ca [2], Mg-Dy-Nd [3], and Mg-Zn-Zr [5] and its corrosion morphology are the focus of papers in this Special Issue.…”

“…An extruded Mg-Dy-Nd alloy during stress corrosion with C-ring compression tests in Ringer solution has been examined in [3]. Microstructural changes during deformation, initial hardness, and strength are used to discuss stress corrosion behavior.…”

Promising Methods for Corrosion Protection of Magnesium Alloys in the Case of Mg-Al, Mg-Mn-Ce and Mg-Zn-Zr: A Recent Progress Review

“…Therefore, the development of effective technologies for corrosion protection is an urgent task to ensure the use of magnesium-containing structures in various fields of application. It should be noted that, 2 of 37 in a contrast to steels or aluminium alloys, magnesium-based alloys exhibit a much higher resistance to stress corrosion cracking (SCC) and they are highly resistant to intergranular and exfoliating corrosion at the same time (except in the case of magnesium-lithium alloys) [1,2].…”