Directionally solidified Mg-4wt-% Zn alloy was prepared and the effect of growth rate on its microstructure evolution and mechanical properties was investigated. A typical cellular structure was observed when the growth rate was lower than 60 µm s⁻¹. The microstructure evolved from cell to columnar dendrite as the growth rate increased. The ultimate tensile strength of the directionally solidified alloy was found to be higher than that of the alloy ingot with the same cooling rate. The ultimate tensile strength of the directionally solidified alloy increased with increasing growth rate but it decreased during the cell–dendrite transition. The results indicate that the mechanical properties of the directionally solidified alloy with fine cellular and columnar dendritic structures meet the requirements of biomaterials.

The mechanical deterioration of Mg alloys during degradation significantly impairs their service performance as biomaterial implants. In the present study, the degradation behavior of a Mg-6Zn-0.5Cu alloy was systematically examined through electrochemical measurements and immersion tests, while the mechanical integrity was assessed via tensile tests under different immersion periods. The results revealed a severe loss in mechanical properties was disproportionate to the corrosion rate. After 7 days’ immersion, the ultimate tensile strength (UTS) and elongation to failure (EL) decreased by 34.4% and 60.1%, respectively, while the corrosion rate was 0.11 mm/y based on the weight loss. This severe mechanical deterioration was primarily caused by pronounced localized corrosion, which induced aggravated local stress concentration at corrosion sites, promoting microcracks initiation and leading to premature fracture of the alloy.

The relative content of strengthening element tantalum (Ta) and oxidation-resistant element chromium (Cr) is an essential value for superalloys to obtain an excellent combination of oxidation resistance and mechanical properties. In the present paper, the isothermal oxidation behavior of several single crystal Ni-base superalloys with different Ta/Cr (wt. %, similarly hereinafter) ratios at 1000 °C in static air has been systematically investigated to explore the optimal Ta/Cr for excellent oxidation resistance. A detailed microstructure study using X-ray diffraction (XRD), scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS) and an electro-probe microanalyzer (EPMA) was performed to reveal the oxidation products and mechanisms. For all alloys, a three-layer structured scale consisting of an outer (Cr, Al, Ti, Ni, Ta)-O layer, an inner Al₂O₃ layer and an inner nitride layer was formed. As Ta/Cr increased, the amounts of Ta-containing products, cracks, holes and inner nitride increased. Meanwhile, the completeness of the Al₂O₃ layer got worse. It was shown that if Ta/Cr ≤ 0.5, Ta increased the growth rate of Cr₂O₃ via the doping effect induced by Ta cations. If Ta/Cr > 0.5, Ta reduced the completeness of Cr₂O₃ through competitive growth of Ta₂O₅ and Cr₂O₃. A good oxidation performance can be expected with the value Ta/Cr ≤ 0.5.

A novel Mg–Zn–Zr–Y–Cu alloy was fabricated, and its corrosion behaviour was investigated in the present work. The results showed that, compared with Mg–6Zn–0.5Zr (ZK60) alloy, Mg–6Zn–1Y–0.5Cu–0.5Zr (ZWCK6100) alloy exhibited finer recrystallised (DRXed) and unDRXed grains, more homogeneous microstructure, and contained CuMgZn and I phase (Mg₃Zn₆Y) in addition to α-Mg, Zn₂Zr, MgZn₂ precipitates. As a result, ZWCK6100 alloy had a lower corrosion rate and higher corrosion resistance, underwent slightly localised corrosion in 3.5 wt-% NaCl solution, implying that the combined addition of Y and Cu was conducive to improving the corrosion resistance of Mg alloys.

In this study, symmetric rolling (SR), unidirectional asymmetric rolling (UASR) and reverse asymmetric rolling (RASR) were conducted in AZ31B alloy, and the corrosion behaviour of AZ31B alloy deformed via these processes mentioned above were studied. The results indicated that samples deformed via the RASR process exhibited a more homogeneous microstructure with refined grains. As a result, samples deformed via the RASR process had the highest open circuit potential (OCP), corrosion potential ( E_corr) and the lowest corrosion current density ( i_corr), underwent slightly localised corrosion, suggesting that the RASR process is beneficial to improve the corrosion resistance of Mg alloy.