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• Ca addition promotes the DRX and grain growth of WZ10 alloy and, consequently, deteriorates mechanical properties. • Absence of Y segregation at the grain boundaries and the associated lack of solute drag to the boundary mobility leads to a pronounced grain growth during SRX in WZX100 alloy. • Partially recrystallized microstructure is a prerequisite at the as-extruded status to form the quadrupole texture and during subsequent annealing, which stands for high formability. • The main influence on the formability seems to be the tilt angle of basal planes in extrusion direction. This paper investigates the influence of addition of Ca in a Y-Zn-containing magnesium alloy on the dynamic and static recrystallization behaviors and reveals the formation mechanism of the quadrupole texture during thermomechanical processing. Direct extrusion of flat bands has been conducted at various process conditions to study the difference between the two alloys WZ10 and WZX100 in terms of microstructure and texture development. It can be shown that, Ca addition promotes the DRX of WZ10 alloy. During additional heat treatment, the absence of Y segregation at the grain boundaries and the associated lack of solute drag to the boundary mobility leads to a pronounced grain growth during SRX in WZX100 alloy. Furthermore, it is shown that the addition of Ca to Y-Zn is not beneficial in terms of formability. It is demonstrated that alloying elements can have different effects depending on the recrystallization mechanisms. Partially recrystallized microstructure is a prerequisite at the as-extruded status to form the quadrupole texture and during subsequent annealing, which stands for high formability. [ABSTRACT FROM AUTHOR]

Mg–RE (Dy, Gd, Y) alloys show promising for being developed as biodegradable medical applications. It is found that the hydride REH 2 could be formed on the surface of samples during their preparations with water cleaning. The amount of formed hydrides in Mg–RE alloys is affected by the content of RE and heat treatments. It increases with the increment of RE content. On the surface of the alloy with T4 treatment the amount of formed hydride REH 2 is higher. In contrast, the amount of REH 2 is lower on the surfaces of as-cast and T6-treated alloys. Their formation mechanism is attributed to the surface reaction of Mg–RE alloys with water. The part of RE in solid solution in Mg matrix plays an important role in influencing the formation of hydrides. [ABSTRACT FROM AUTHOR]

Previous investigations indicate that the creep resistance of magnesium alloys is proportional to the stability of precipitated intermetallic phases at grain boundaries. These stable intermetallic phases were considered to be effective to suppress the deformation by grain boundary sliding, leading to the improvement of creep properties. Based on this point, adding the alloying elements to form the stable intermetallics with high melting point became a popular way to develop the new creep resistant magnesium alloys. The present investigation, however, shows that the creep properties of binary Mg–Sn alloy are still poor even though the addition of Sn possibly results in the precipitation of thermal stable Mg 2 Sn at grain boundaries. That means other possible mechanisms function to affect the creep response. It is finally found that the poor creep resistance is attributed to the segregation of Sn at dendritic and grain boundaries. Based on this observation, new approaches to improve the creep resistance are suggested for magnesium alloys because most currently magnesium alloys have the commonality with the Mg–Sn alloys. [ABSTRACT FROM AUTHOR]

Abstract: The present work investigates the influences of microalloying with rare earths on the mechanical properties of magnesium alloys. The amount of each rare earth element is controlled below 0.4 wt.% in order not to increase the cost of alloy largely. The synergic effects from the multi-microalloying with rare earths on the mechanical properties are explored. The obtained results show that the as-cast magnesium alloys multi-microalloying with rare earths possesses a quite high ductility with a tensile strain up to 25–30% at room temperature. Moreover, these alloys exhibit much better corrosion resistance than AZ31 alloy. The preliminary in situ neutron diffractions on the deformation of these alloys indicate that the multi-microalloying with rare earths seems to be beneficial for the activation of more slip systems. The deformation becomes more homogeneous and the resultant textures after deformation are weakened. [Copyright &y& Elsevier]

The growth of plasma electrolytic oxidation (PEO) coatings can be considered a complex process that includes discharge breakdown, sintering, and deposition process. In this work, inert SiO 2 and La 2 O 3 particles were used as tracers to investigate the formation mechanisms of PEO coatings on Mg alloy AM50. The growth direction and kinetics of the coating formation are primarily controlled by the intensity and the number of discharges. High-intensity discharges enable the inward growth of the PEO coating rapidly. Low-intensity discharges allow the outward growth of the coating at a slow speed. At the initial stage of a treatment, conversion products form locally around the intermetallics and disseminate gradually. Discharges appear after reaching the breakdown potential, leading to rapid growth of the coating. The outward growth of the layer is non-uniform because the protruding conversion products are the last locations converted by the discharges. Inward growth of the layer occurs preferentially around intermetallic phases and the formation of the inner layer is related to the inward growth. [ABSTRACT FROM AUTHOR]

Photocatalytically active plasma electrolytic oxidation coatings on AM50 Mg alloy are reported in the present work. The photocatalytic activity was achieved via introduction of anatase (TiO 2 particles) to the treatment bath. The photocatalytic performance of the coating was evaluated by measuring the degradation rate of aqueous methylene blue solution and was primarily related to the anatase content on the coating surface. Lower treatment voltage and a higher amount of particles in the electrolyte can be used to incorporate more anatase into the layer and generate superior photocatalytic coatings. The tailored and functionalized surface provides new functionality for magnesium alloys. [ABSTRACT FROM AUTHOR]

The addition of particles into plasma electrolytic oxidation (PEO) electrolyte provides a possibility to produce functionalized coatings with a wider range of compositions and new phases. In this study, nano- and micro-sized SiO 2 particles were in-situ incorporated into phosphate-based coatings and the effect of these particles on the microstructure, composition and properties of the coatings was investigated. It was observed that the size and the melting point of the particles have a synergistic effect on the uptake and incorporation mode. The uptake of the nanoparticles occurred mainly via discharge channels and open pores, while micro-sized particles were mainly absorbed via the coating surface. Different particle properties result in reactive and inert incorporation for the nano- and micro-sized SiO 2 particles, respectively. The results show that particle additions improve the wear resistance of PEO coating, although corrosion resistance is slightly reduced. Due to superior wear performance and degradability, PEO coatings with reactively incorporated nanoparticles on Mg alloy might be suitable for bio-medical application. [ABSTRACT FROM AUTHOR]

Abstract: The microstructure, mechanical properties and fatigue crack propagation (FCP) of extruded magnesium alloy AM60 were investigated and compared with rolled AM60. The extruded AM60 has an inhomogeneous microstructure characterized by α-matrix, β phases and Al–Mn precipitates and denuded zones as well, whereas rolled AM60 has fine grains. The change in strain-hardening exponent of extruded AM60 with strain rate is ascribed to inhomogeneous microstructure. In situ double twinning: and occurred during FCP of extruded alloy. Its crack initiation and growth are related to slip bands, double twinning and intermetallic compounds. Small cracks resulted from oxide and intermetallic compounds in rolled AM60 may be responsible for oscillatory crack growth and crack arrest. Extruded AM60 has a slower FCP rate than rolled one. [Copyright &y& Elsevier]

Abstract: Biodegradable metals are breaking the current paradigm in biomaterial science to develop only corrosion resistant metals. In particular, metals which consist of trace elements existing in the human body are promising candidates for temporary implant materials. These implants would be temporarily needed to provide mechanical support during the healing process of the injured or pathological tissue. Magnesium and its alloys have been investigated recently by many authors as a suitable biodegradable biomaterial. In this investigative review we would like to summarize the latest achievements and comment on the selection and use, test methods and the approaches to develop and produce magnesium alloys that are intended to perform clinically with an appropriate host response. [Copyright &y& Elsevier]