关键词： Magnesium alloy   Extrusion   Creep mechanism   Microstructure evolution   Precipitation   Rare earths  

摘要： In this research,the microstructure evolution,mechanical properties,and creep mechanisms of Mg-12 Gd-1 MM-0.6 Zr(wt%)alloy under different conditions were systematically studied using scanning electron microscopy(SEM),transmission electron microscopy(TEM),X-ray diffraction(XRD),and tensile creep *** the microstructure of the as-cast sample,the average grain size is about 42μm,and the eutectic compounds were determined to be Mg_(5)(Gd_(0.8)MM_(0.2)).During homogenization,these eutectic compounds gradually dissolve,and Mg_(12)MM particles are *** hot extrusion,complete dynamic recrystallization(DRX)occurs,resulting in equiaxial grains with an average grain size of about 12μm and the formation of streamlines consisting of Mg_(12)MM particles along the extrusion direction(ED).After T5 treatment(225℃for 7 h),a large number ofβ'(Mg_(7)Gd)phases are precipitated on the{11-20}αhabit plane and are interconnected,forming an interlaced network *** ultimate tensile strength(R_(m)=405 MPa)and yield strength(R_(P0.2)=288 MPa)of the T5 sample are significantly higher than those of the as-extruded sample(R_(m)=289 MPa,R_(P0.2)=185 MPa),but the elongation(A=4%)was remarkably lower than that of the as-extruded sample(A=18%).When crept at225℃under 100 MPa,the steady-state creep rates of the as-cast,as-extruded,and T5 samples are1.59×10^(-8),1.08×10^(-8),and 1.40×10^(-8)s^(-1),respectively,and their total strains within 100 h are respectively breaking,0.81%,and 0.92%,indicating that the as-extruded alloy exhibits the best creep *** analysis reveals that,during the creep process of the T5 sample,theβ'particles coarsen and the precipitate-free zones(PFZs)widen,which increase the steady-state creep rate and the total strain within 100 h as compared with the as-extruded sample.

关键词： AZ31-xGd镁合金   时效处理   显微组织   弥散强化   析出强化  

摘要： 研究了时效处理对含Gd的AZ31镁合金显微组织和力学性能的影响,通过SEM,EDS对合金的显微结构进行了表征。结果表明,AZ31镁合金中添加Gd后,优先形成了高熔点的Al2Gd相,抑制了Mg17Al12相的生成;且随Gd含量的增加铸态合金的显微硬度呈现先增加后减小的趋势。对AZ31-xGd合金进行时效硬度分析,由时效硬化曲线确定了最佳T6处理工艺(500℃,16 h)+(200℃,32 h)。在时效过程中,Al2Gd相从颗粒状变为针状,再转变为短杆状最后团聚变成块状。铸态和时效态合金的力学性能随Gd含量的增加呈先增加后减小的趋势,这是由于时效析出的Al2Gd相具有弥散强化和析出强化的作用。

关键词： 内固定结合人工椎体成形术   老年骨质疏松   椎体骨折  

摘要： 探讨内固定结合人工椎体成形术治疗胸腰椎骨折的临床效果。方法:选取我院2018年6月至2020年6月收治的胸腰椎骨折患者为研究对象。共选择64例患者纳入研究范围,分为对照组和实验组。各32例,对照组采用常规护理方法,实验组采用内固定结合人工椎体成形术。结果:实验组治疗效果明显优于对照组,相关研究有统计学意义。结论:内固定结合人工椎体成形术在胸腰椎骨折患者针对性护理中的应用,能有效改善老年人的运动功能,得到患者及其家属的认可,值得在临床实践中进一步推广应用。

关键词： 镁合金   干滑动   摩擦   磨损  

摘要： 镁合金被广泛应用于航空航天、汽车及军事等领域,但其摩擦学性能对零部件的服役寿命和可靠性具有重大影响。本研究采用往复式球-盘摩擦方式,通过与GCr15钢球配副,研究干摩擦条件下AZ80A、ZK60A和ME20M镁合金在不同滑动速度和载荷条件下的摩擦磨损行为。采用扫描电子显微镜和能谱仪分析镁合金的显微结构及磨损机理。结果表明:当滑动速度超过0.10 m/s时,随着速度的增加,合金的摩擦系数逐渐降低,而磨损率则先减小后增大,其原因在于摩擦热的作用导致摩擦表面形成了氧化物,同时材料表面软化,剪切力降低,使摩擦系数和磨损率不断减小;当滑动速度增加到0.20 m/s时,摩擦表面温度升高,金属软化导致磨损表面金属氧化物剥落,增大了合金的磨损率。随着载荷的增加,合金的摩擦系数和磨损率持续降低。干摩擦条件下镁合金的磨损机理逐渐由磨粒磨损和塑性变形转变为磨粒磨损、氧化磨损、粘着磨损和塑性变形。与ZK60A和ME20M相比,AZ80A镁合金表现出较好的摩擦学性能,这归因于合金的高硬度、β-Mg_(17)Al_(12)硬质相的支撑作用以及摩擦过程中形成的氧化物。

关键词： 镁合金   耐腐蚀性   深冷处理  

摘要： 镁及镁合金是一种应用较为广泛的金属材料,但因其较差的耐腐蚀性能而受限于海洋环境应用。基于此,文章结合笔者相关经验,就镁合金的腐蚀机理进行简要分析,同时提出改善镁合金耐腐蚀性的些许建议以供参考。

关键词： 溶胶-凝胶   掺铝氧化锌薄膜   镁合金   微弧氧化膜   制备   耐蚀性   导电性  

摘要： 为了对镁合金表面微弧氧化陶瓷膜进行导电改性,采用溶胶-凝胶法在镁合金微弧氧化膜表面制备了掺铝氧化锌(ZnO:Al,AZO)透明导电薄膜。通过X射线衍射仪(XRD)、场发射扫描电镜(FE-SEM)、盐雾试验、四探针测试仪等分析测试手段,研究了涂膜层数和退火温度对AZO薄膜的表面形貌、微观结构、耐蚀性和导电性的影响。结果表明:所制备的导电薄膜由c轴择优取向的六角纤锌矿结构的晶体构成;随着涂膜层数和退火温度的增加,薄膜的方块电阻降低。制备的AZO薄膜自身的耐蚀性较差,并且增加涂膜层数并不能明显改善导电薄膜的耐蚀性。通过研究影响膜层耐蚀性的主要因素,为今后进一步优化工艺从而改善透明导电薄膜的耐蚀性奠定了基础。

关键词： plasma electrolytic oxidation   alumina nanoparticle   wear   corrosion  

摘要： The synthesis of ceramic coatings via conversion of metallic surface is the main route of corrosion resistance in the magnesium alloys. Using ceramic nano-particles as sealant in these coatings is very useful. In this study, the effect of applied current density and treatment duration on the alumina nanoparticle incorporation, corrosion resistance, and wear behavior of plasma electrolytic oxidation coating on AZ31 alloy was investigated. The results showed that the highest incorporation of nanoparticles occurs at a current density of 100 mA/cm(2) during 10 min while at higher current densities or treatment durations, the eruption of molten oxide prevents the embedding of nanoparticles inside the coating. The high incorporation of nanoparticles increased the homogeneity and compaction of the coating which caused the highest corrosion and wear resistance.

关键词： Selective laser melting   finite element analysis   porous dental implants   mechanical properties   osteoblast proliferation  

摘要： In this paper, a complex porous dental implant with biodegradable magnesium alloy was designed based on selective laser melting (SLM). Finite element analysis (FEA) was used to simulate the stress distribution of dental implant and alveolar bone in two models of preliminary and later stages of implant. The stress concentration area of dental implants was found not in the porous structure, and the weak part of mechanical properties accords with the work requirements. The porous structure of dental implants can promote the function of cancellous bone in the process of conducting the stress of the dental implant, thus improving the bearing capacity of dental *** vitrofatigue experiments were carried out on the experimental samples produced by 3D printing. Through the cell contrast experiment, it was proved that the decomposed Mg(2+)could reach the titanium surface smoothly through the porous structure and complete the proliferation of osteoblasts.

关键词： Friction stir butt welding   Mg/steel dissimilar metal   Truncated cone-shaped stirring pin   Steel-strip  

摘要： A truncated cone-shaped stirring pin with threads was designed to enhance friction stir butt welding (FSBW) quality of AZ31B magnesium alloy and Q235 low carbon steel. The effects of welding speed and rotation speed on the microstructure and properties of joints were studied. Microstructure characteristics and element distribution along the Mg/steel interface were analyzed. The results showed that the truncated cone-shaped stirring pin with threads effectively improves the metal flow behavior, especially the fluidity of steel. A steel-strip was formed at the bottom of the Mg side weld nugget during the welding process. The stirring pin effectively improved the interfacial reaction at the Mg/steel dissimilar metal. A thin accumulation layer of the Al was observed along with the interface. Discontinuous oxides of Mg appeared in the interface and were mainly distributed in the upper and bottom interfaces of the joint. As the heat input increased, the metallurgical bonding of the Mg/steel interface became stronger, and the joint strength increased. But when the heat input increased to a certain level, the oxidation of the Mg/steel interface became serious. The aggregation of MgO in the Mg/steel interface led to cracks, which decreased the joint strength. When the welding speed was 75 mm/min and the rotation speed was 850 rpm, the highest tensile strength of the joint was 189.4 MPa, which is 75.8 % of magnesium alloy. The joint fractured in the Mg side near the Mg/steel interface.

关键词： magnesium alloy   AM60   biobased coating   PA11   silicon-based coating   polyester lacquer   food contact   chemically aggressive environment   specific migration  

摘要： Low-cost, environmentally friendly and easily applicable coating for Mg alloys, able to resist in real world conditions, are studied. Coatings already used for other metals (aluminum, steel) and never tested on Mg alloy for its different surface and reactivity were deposited on AM60 magnesium alloys to facilitate their technological applications, also in presence of chemically aggressive conditions. A biobased PA11 powder coating was compared to synthetic silicon-based and polyester coatings, producing lab scale samples, probed by drop deposition tests and dipping in increasingly aggressive, salty, basic and acid solutions, at RT and at higher temperatures. Coatings were analyzed by SEM/EDX to assess their morphology and compositions, by optical and IR-ATR microscopy analyses, before and after the drop tests. Migration analyses from the samples were performed by immersion tests using food simulants followed by ICP-OES analysis of the recovered simulant to explore applications also in the food contact field. A 30 mu m thick white lacquer and a 120 mu m PA11 coating resulted the best solutions. The thinner siliconic and lacquer coatings, appearing brittle and thin in the SEM analysis, failed some drop and/or dipping test, with damages especially at the edges. The larger thickness is thus the unique solution for edgy or pointy samples. Finally, coffee cups in AM60 alloy were produced, as real word prototypes, with the best performing coatings and tested for both migration by dipping, simulating also real world aging (2 h in acetic acid at 70 degrees and 24 h in hot coffee at 60 degrees C): PA11 resulted stable in all the tests and no migration of toxic metals was observed, resulting a promising candidate for many real world application in chemically aggressive environments and also food and beverage related applications.