Cast aluminum alloys have been widely used in aerospace and automotive lightweight fields due to their high specific strength, low density and high fracture toughness. In this paper, six alloys are designed to reveal the role of the individual and joint addition of minor Ti, Mn, Cr, Zr and Er in the cast Al-Zn-Mg-Cu alloys. The results show that the addition of Ti can significantly refine the ingot grains. The addition of Mn and Cr forms Al(Fe,Mn,Cr) and Al5(Fe,Mn)Si2 phases and consequently reduces the impurity elements Fe and Si in the matrix. The joint addition of Ti, Mn, Cr, Zr, and Er produces a poison effect, forming a bulk composite phase containing Al8Cu4Er, Al12(Mn,Cr), and Al3Ti. After solution treatment, a large amount of Al12(Mn,Cr) precipitates are formed in the alloy containing Cr and Mn, and plenty of dispersed spherical Al3(Er,Zr) particles are precipitated out of the alloy with Zr and Er, playing a second phase strengthening effect on the alloys. However, the most important strengthening phase in all alloys is still η’ phase precipitated in the aging process, and its precipitation behavior is not affected by the addition of these alloying elements, so the aging hardening curves of all the alloys show a similar trend. As a result, the hardness of the alloy with joint addition of Ti, Mn, Cr, Zr, and Er is the highest after both solution and aging treatments, which is attributed to the collaborative strengthening effects of Al12(Mn,Cr) and Al3(Er,Zr) particles formed upon solution treatment and η’ phase precipitated upon aging.

Diabetes mellitus, an epidemic with a rapidly increasing number of patients, always leads to delayed wound healing associated with consistent pro-inflammatory M1 polarization, decreased angiogenesis and increased reactive oxygen species (ROS) in the microenvironment. Herein, a poly (lactic-co-glycolic acid) (PLGA)-based microneedle patch loaded with magnesium hydride (MgH2) (MN-MgH2) is manufactured for defeating diabetic wounds. The application of microneedle patch contributes to the transdermal delivery and the prolonged release of MgH2 that can generate hydrogen (H2) and magnesium ions (Mg2+) after reaction with body fluids. The released H2 reduces the production of ROS, transforming the pathological microenvironment induced by diabetes mellitus. Meanwhile, the released Mg2+ promotes the polarization of pro-healing M2 macrophages. Consequently, cell proliferation and migration are improved, and angiogenesis and tissue regeneration are enhanced. Such intelligent microneedle patch provides a novel way for accelerating wound healing through steadily preserving and releasing of H2 and Mg2+ locally and sustainably.

A method of forming an Mg/Al intermetallic compound coating enriched with Mg17Al12 and Mg2Al3 was developed by heat treatment of electrodeposition Al coatings on Mg alloy at 350 °C. The composition of the Mg/Al intermetallic compounds could be tuned by changing the thickness of the Zn immersion layer. The morphology and composition of the Mg/Al intermetallic compound coatings were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), and electron backscattered diffraction (EBSD). Nanomechanical properties were investigated via nano-hardness (nHV) and the elastic modulus (EIT), and the corrosion behavior was studied through hydrogen evolution and potentiodynamic (PD) polarization. The compact and uniform Al coating was electrodeposited on the Zn-immersed AZ91D substrate. After heat treatment, Mg2Al3 and Mg17Al12 phases formed, and as the thickness of the Zn layer increased from 0.2 to 1.8 μm, the ratio of Mg2Al3 and Mg17Al12 varied from 1:1 to 4:1. The nano-hardness increased to 2.4 ± 0.5 GPa and further improved to 3.5 ± 0.1 GPa. The Mg/Al intermetallic compound coating exhibited excellent corrosion resistance and had a prominent effect on the protection of the Mg alloy matrix. The control over the ratio of intermetallic compounds by varying the thickness of the Zn immersion layer can be an effective approach to achieve the optimal comprehensive performance. As the Zn immersion time was 4 min, the obtained intermetallic compounds had relatively excellent comprehensive properties.

Effects of NaI as an additive on electrodeposition of Al coatings in AlCl3-NaCl-KCl (80-10-10 wt-%) molten salts electrolyte at 150 °C were investigated by means of cyclic voltammetry, chronopotentiometry, scanning electron microscopy and X-ray diffraction (XRD). Results reveal that addition of NaI in the electrolyte intensifies cathodic polarization, inhibits growth of Al deposits and increases number density of charged particles. The electrodeposition of Al coatings in the AlCl3-NaCl-KCl molten salts electrolyte proceeds via three-dimensional instantaneous nucleation which however exhibits irrelevance with NaI. Galvanostatic deposition results indicate that NaI could facilitate the formation of uniform Al deposits. A compact coating consisting of Al deposits with an average particle size of 3 μm was obtained at a current density of 50 mA∙cm−2 in AlCl3-NaCl-KCl molten salts electrolyte with 10 wt-% NaI. XRD analysis confirmed that NaI could contribute to the formation of Al coating with a preferred crystallographic orientation along (220) plane.

The Al coatings achieved via electrodeposition on a Cu electrode from AlCl3-NaCl-KCl (80–10–10 wt.%) molten salts electrolyte with Tetramethylammonium Chloride (TMACl) and Sodium Iodide (NaI) additives is reported. The effect of the two additives on electrodeposition were investigated by cyclic voltammetry (CV), chronopotentiometry (CP), scanning electron microscopy (SEM) and X-ray diffraction (XRD). Results reveal that compact and smooth Al coatings are obtained at 150 °C by the electrodeposition process from the electrolyte with 1% TMACl and 10% NaI. The Al coatings exhibit great corrosion resistance close to that of pure Al plate, with a corrosion current of 3.625 μA. The average particle size is approximately 2 ± 1 μm and the average thickness of the Al layer is approximately 7 ± 2 μm. The nucleation/growth process exhibits irrelevance with TMACl or NaI during the electrodeposition of Al. TMACl cannot affect and improve the electrodeposition effectively. However, the addition of TMACl and NaI can intensify the cathodic polarization, producing an inhibition of Al deposition, and contribute to form uniform Al deposits. This can increase the conductivity and facilitate in refining the size of Al particles, contributing to forming a continuous, dense and uniform layer of Al coating, which can be used as effective additives in molten salts electrolyte.

镁合金具有质轻,比强度和比模量高,加工性、减震性和抗冲击性好,环保易回收和电磁屏蔽性能良好等优点,在军事、航空、汽车、电子通讯等领域具有广泛的应用.但镁合金极易发生腐蚀,因此,镁合金在使用前必须进行有效的表面防护处理.在诸多的表面处理方法中,镁合金表面镀覆铝层不仅具有良好的耐腐蚀性和耐摩擦磨损性,还可保持镁合金的金属属性,同时具有轻质、易回收等优点,一直是研究和关注的热点.镁合金表面镀覆铝层的方法主要有:喷涂法、液体扩散法、渗铝法、高能束熔覆法和沉积法.沉积法又包括溅射沉积、物理/化学气相沉积、电沉积.其中电沉积法因其设备简单、操作方便、成本低廉,且镀层的厚度和质量可控,引起了研究者们的广泛关注.电沉积铝技术主要包括前处理工艺、电解液种类、电沉积工艺参数、镀后处理工艺和镀层性能等几个方面.镁合金电沉积铝前处理工艺十分关键,主要包括机械打磨、碱性除油、酸性浸蚀、活化处理和预沉积金属底层.电沉积铝电解液分为有机溶剂、离子液体和无机熔盐三类.其中,有机溶剂易挥发,现在已很少使用;离子液体绿色环保,但成本高;无机熔盐成本低,但沉积温度高,对仪器设备要求较高.电沉积工艺参数与常规水溶液相似,主要包括电流密度、电沉积温度、搅拌速率、添加剂和水含量.需要特别注意的是水含量,水汽的引入将严重影响镀层质量甚至无法电沉积铝.电沉积铝镀层与基体结合力不好是目前存在的主要问题之一,因此镀后处理工艺非常重要,镀后处理包括热处理和阳极氧化处理.热处理可在镀层与界面处形成冶金结合,显著提高镀层结合力;阳极氧化可进一步提高镀层耐腐蚀性和硬度.另外,合金化是提高镀层综合性能的有效方法之一.本文针对镁合金表面电沉积铝镀层技术,从镁合金前处理、电解液类型、电沉积铝工艺参数和镀层后处理与性能四个方面的研究现状进行了阐述,并在文献综述的基础上,结合本课题组在铝镀层方面的研究经验,对镁合金表面电沉积铝的技术难点进行了分析,并对未来的发展方向进行了展望.