Development and prospects of degradable magnesium alloys for structural and functional applications in the fields of environment and energy

Magnesium and its alloys have such advantages with lightweight, high specific strength, good damping, high castability and machinability,which make them an attractive choice for applications where weight reduction is important, such as in the aerospace and automotive industries.However, their practical applications are still limited because of their poor corrosion resistance, low high temperature strength and ambient formability. Based on such their property shortcomings, recently degradable magnesium alloys were developed for broadening their potential applications. Considering the degradable Mg alloys for medical applications were well reviewed, the present review put an emphasis on such degradable magnesium alloys for structural and functional applications, especially the applications in the environmental and energy fields. Their applications as fracture ball in fossil energy, sacrificial anode, washing ball, and as battery anodes, transient electronics, were summarized. The roles of alloying elements in magnesium and the design concept of such degradable magnesium alloys were discussed. The existing challenges for extending their future applications are explored.

Influence of Ca addition on the dynamic and static recrystallization behavior of direct extruded flat profiles of Mg-Y-Zn alloy

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.

四肢组织工程骨新型支架的比较研究

现代医学的骨组织工程中，种子细胞、生物材料和组织构建是三个最基本要素，而生物材料或支架材料是影响组织构建最为关键的因素之一。它必须具有良好的生物相容性、可降解性、低免疫原性以及一定的空间结构、孔隙率、降解速率等特性。

Recent research and developments on wrought magnesium alloys

Wrought magnesium alloys attract special interests as lightweight structural material due to their homogeneous microstructure and enhanced mechanical properties compared to as-cast alloys.In this contribution,recent research and developments on wrought magnesium alloys are reviewed from the viewpoint of the alloy design,focusing on Mg-Al,Mg-Zn and Mg-rare earth(RE)systems.The effects of different alloying elements on the microstructure and mechanical properties are described considering their strengthening mechanisms,e.g.grain refinement,precipitation and texture hardening effect.Finally,the new alloy design and also the future research of wrought magnesium alloys to improve their mechanical properties are discussed.

Role of multi-microalloying by rare earth elements in ductilization of magnesium alloys

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.

添加铈对高压压铸AM50镁合金显微组织和力学性能的影响(英文)

研究添加铈对高压压铸AM50镁合金显微组织和力学性能的影响。结果表明:添加铈能使AM50镁合金晶粒细化,并使其室温和高温力学性能得到显著改善。相对于未添加Ce和添加0.5%Ce(质量分数)的AM50镁合金,添加1%Ce(质量分数)的镁合金的晶粒更细,力学性能更优。

Unexpected formation of hydrides in heavy rare earth containing magnesium alloys

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 REH2 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.

Understanding effects of microstructural inhomogeneity on creep response-New approaches to improve the creep resistance in magnesium alloys

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.

Influence of incorporating Si_(3)N_(4) particles into the oxide layer produced by plasma electrolytic oxidation on AM50 Mg alloy on coating morphology and corrosion properties

The influence of incorporating different sizes of Si_(3)N_(4) particles on the microstructure and corrosion properties of a phosphate-based plasma electrolytic oxidation (PEO) coating on AM50 magnesium alloy was investigated. The experiments for this study were performed in alkaline electrolytes containing 1 g/L KOH, 10 g/L Na_(3)PO_(4) with and without three different sized of Si_(3)N_(4) particles. The corrosion properties of PEO coatings were investigated by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) in 0.5 wt.% NaCl solution. Microstructure observations by SEM showed that the surface morphology and composition of the PEO coating were affected greatly by particle addition. Si_(3)N_(4) particles can still be found without decomposition in the final coating due to their high melting point.

添加CaO或Y的ZK40镁合金的腐蚀行为（英文）

研究了铸造ZK40、添加2%(质量分数)CaO和添加1%(质量分数)Y的ZK40镁合金的微观组织,并表征了金属间化合物相的形貌和分布。利用ZK40晶界处分散的金属间化合物颗粒,将添加了CaO或Y的ZK40的微观组织调整为沿晶界分布的金属间化合物的半连续网络结构。微观组织中没有检测到CaO,Ca存在于铸造过程中形成的金属间化合物Ca_2Mg_6Zn_3中。析氢和电化学交流阻抗谱分析显示,添加CaO后合金的耐腐性略有提高,而添加Y却对ZK40的耐腐蚀性有负面影响。浸泡试验结果显示,严重的局部腐蚀和沿金属间化合物的腐蚀对ZK40-Y合金的腐蚀过程有重要影响,而ZK40和ZK40-CaO合金的局部腐蚀不明显。ZK40合金中α-Mg基体中的显微偏析明显高于加CaO或Y的ZK40合金,这种作用结合合金表面形成了更加稳定的耐腐蚀层是ZK40-CaO合金的耐腐蚀性能提高的主要原因。

Recycling of magnesium drive train components

With the development of new heat resistant magnesium alloys, the automotive industry has introduced several parts to the drive train. The rising number of large magnesium components will result in a higher quantity of automotive post consumer scrap. It was the aim of this work to find a reasonable alloy system for the recycling of these magnesium drive train components. A matrix of potential recy-cling alloys based on the magnesium alloy AM50 was prepared via permanent mould casting. The materials were investigated via tensile testing, creep tests and salt spray tests. Three alloys were selected for processing via high pressure die casting and the tests were repeated on the new materials. A promising system for recycling has been isolated and will be investigated more deeply for the influence of impurities.